<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Air embolism and can you explain it in depth? [/INST] An air embolism, also known as a  gas embolism, is a blood vessel blockage caused by one or more bubbles of air or other gas in the circulatory system. Air can be introduced into the circulation during surgical procedures, lung over-expansion injury, decompression, and a few other causes. Air embolisms may also occur in the xylem of vascular plants, especially when suffering from water stress.
Divers can develop arterial gas embolisms as a consequence of lung over-expansion injuries. Breathing gas introduced into the venous system of the lungs  due to pulmonary barotrauma will not be trapped in the alveolar capillaries, and will consequently be circulated to the rest of the body through the systemic arteries, with a high risk of embolism. Inert gas bubbles arising from decompression are generally formed in the venous side of the systemic circulation, where inert gas concentrations are highest, these bubbles are generally trapped in the capillaries of the lungs where they will usually be eliminated without causing symptoms. If they are shunted to the systemic circulation through a patent foramen ovale they can travel to and lodge in the brain where they can cause stroke, the coronary capillaries where they can cause myocardial ischaemia or other tissues, where the consequences are usually less critical. The first aid treatment is to administer oxygen at the highest practicable concentration, treat for shock and transport to a hospital where therapeutic recompression and hyperbaric oxygen therapy are the definitive treatment.

Signs and symptoms
In surgery
Symptoms include:
Hypotension
Shortness of breath

In divers
Symptoms of arterial gas embolism include:
Loss of consciousness
Cessation of breathing
Vertigo
Convulsions
Tremors
Loss of coordination
Loss of control of bodily functions
Numbness
Paralysis
Extreme fatigue
Weakness in the extremities
Areas of abnormal sensation
Visual abnormalities
Hearing abnormalities
Personality changes
Cognitive impairment
Nausea or vomiting
Bloody sputum
Symptoms of other consequences of lung overexpansion such as pneumothorax, subcutaneous or mediastinal emphysema may also be present.

Causes
Interventional procedures
Interventional radiology procedures, cardiac, and neurosurgical procedures can predispose to air embolism. Besides, increasing use of pump injectors for contrast delivery, and percutaneous intervention to the lungs also increases the risk of air embolism.

Decompression illness
Gas embolism is a diving disorder experienced by underwater divers who breathe gases at ambient pressure, and can happen in two distinct ways:

Pulmonary barotrauma:  Air bubbles can enter the bloodstream as a result of gross trauma to the lining of the lung following a rapid ascent while holding the breath; the air held within the lung expands to the point where the tissues tear (pulmonary barotrauma).  This is easy to do as the lungs give little warning through pain until they do burst.  The diver will usually arrive at the surface in pain and distress and may froth or spit blood.  A pulmonary barotrauma is usually obvious and may present quite differently from decompression sickness.
Decompression sickness: Inert gas bubbles form in the bloodstream if the gas dissolved in the blood under pressure during the dive is not allowed sufficient time to be eliminated in solution on ascent. The symptoms may be subtle and not immediately noticeable, and may develop for some time after surfacing.

Ventilator induced pulmonary barotrauma
Trauma to the lung can also cause an air embolism. This may happen after a patient is placed on a ventilator and air is forced into an injured vein or artery, causing sudden death. Breath-holding while ascending from scuba diving may also force lung air into pulmonary arteries or veins in a similar manner, due to the pressure difference.

Direct injection
Air can be injected directly into a vein or artery accidentally during clinical procedures. Misuse of a syringe to meticulously remove air from the vascular tubing of a hemodialysis circuit can allow air into the vascular system. Venous air embolism is a rare complication of diagnostic and therapeutic procedures requiring catheterization of a vein or artery. If a significant embolism occurs, the cardiovascular, pulmonary, or central nervous system may be affected. Interventions to remove or mitigate the embolism may include procedures to reduce bubble size, or withdrawal of air from the right atrium.The lethal dose for humans is considered theoretically between 3 and 5 ml per kg. It is estimated that 300-500 ml of gas introduced at a rate of 100 ml per sec would prove fatal.

Mechanism
Air embolism can occur whenever a blood vessel is open and a pressure gradient exists favoring entry of gas. Because the circulatory pressure in most arteries and veins is greater than atmospheric pressure, an air embolus does not often happen when a blood vessel is injured. In the veins above the heart, such as in the head and neck, the venous pressure may be less than atmospheric and an injury may let air in. This is one reason why surgeons must be particularly careful when operating on the brain, and why the head of the bed is tilted down when inserting or removing a central venous catheter from the jugular or subclavian veins.When air enters the veins, it travels to the right side of the heart, and then to the lungs. This can cause the vessels of the lung to constrict, raising the pressure in the right side of the heart. If the pressure rises high enough in a patient who is one of the 20% to 30% of the population with a patent foramen ovale, the gas bubble can then travel to the left side of the heart, and on to the brain or coronary arteries. Such bubbles are responsible for the most serious of gas embolic symptoms.
Venous or pulmonary air embolism occurs when air enters the systemic veins and is transported to the right side of the heart and from there into the pulmonary arteries, where it may lodge, blocking or reducing blood flow. Gas in the venous circulation can cause cardiac problems by obstructing the pulmonary circulation or forming an air-lock which raises central venous pressure and reduces pulmonary and systemic arterial pressures. Experiments on animals show that the amount of gas necessary for this to happen is quite variable. Human case reports suggest that injecting more than 100 mL of air into the venous system at rates greater than 100 mL/s can be fatal. Very large and symptomatic amounts of venous air emboli may also occur in rapid decompression in severe diving or decompression accidents, where they may interfere with circulation in the lungs and result in respiratory distress and hypoxia.Gas embolism in a systemic artery, termed arterial gas embolism (AGE), is a more serious matter than in a vein, because a gas bubble in an artery may directly stop blood flow to an area fed by the artery. The symptoms of AGE depend on the area of blood flow, and may be those of stroke for a cerebral arterial gas embolism (CAGE) or heart attack if the heart is affected. The amount of arterial gas embolism that causes symptoms depends on location — 2 mL of air in the cerebral circulation can be fatal, while 0.5 mL of air into a coronary artery can cause cardiac arrest.

Prevention and screening
If a patent foramen ovale (PFO) is suspected, an examination by echocardiography may be performed to diagnose the defect. In this test, very fine bubbles are introduced into a patients vein by agitating saline in a syringe to produce the bubbles, then injecting them into an arm vein. A few seconds later, these bubbles may be clearly seen in the ultrasound image, as they travel through the patients right atrium and ventricle. At this time, bubbles may be observed directly crossing a septal defect, or else a patent foramen ovale may be opened temporarily by asking the patient to perform the Valsalva maneuver while the bubbles are crossing through the right heart – an action which will open the foramen flap and show bubbles passing into the left heart. Such bubbles are too small to cause harm in the test, but such a diagnosis may alert the patient to possible problems which may occur from larger bubbles, formed during activities like underwater diving, where bubbles may grow during decompression. A PFO test may be recommended for divers intending to expose themselves to relatively high decompression stress in deep technical diving.

Diagnosis
As a general rule, any diver who has breathed gas under pressure at any depth who surfaces unconscious, loses consciousness soon after surfacing, or displays neurological symptoms within about 10 minutes of surfacing should be assumed to be experiencing arterial gas embolism.Symptoms of arterial gas embolism may be present but masked by environmental effects such as hypothermia, or pain from other obvious causes. Neurological examination is recommended when there is suspicion of lung overexpansion injury. Symptoms of decompression sickness may be very similar to, and confused with, symptoms of arterial gas embolism, however, treatment is basically the same. Discrimination between gas embolism and decompression sickness may be difficult for injured divers, and both may occur simultaneously. Dive history may eliminate decompression sickness in many cases, and the presence of symptoms of other lung overexpansion injury would raise the probability of gas embolism.

Treatment
A large bubble of air in the heart (as can follow certain traumas in which air freely gains access to large veins) will present with a constant "machinery" murmur. It is important to promptly place the patient in Trendelenburg position (head down) and on their left side (left lateral decubitus position). The Trendelendburg position keeps a left-ventricular air bubble away from the coronary artery ostia (which are near the aortic valve) so that air bubbles do not enter and occlude the coronary arteries (which would cause a heart attack). Left lateral decubitus positioning helps to trap air in the non-dependent segment of the right ventricle (where it is more likely to remain instead of progressing into the pulmonary artery and occluding it). The left lateral decubitus position also prevents the air from passing through a potentially patent foramen ovale (present in as many as 30% of adults) and entering the left ventricle, from which it could then embolise to distal arteries (potentially causing occlusive symptoms such as stroke).Administration of high percentage oxygen is recommended for both venous and arterial air embolism. This is intended to counteract ischaemia and accelerate bubble size reduction.For venous air embolism the Trendelenburg or left lateral positioning of a patient with an air-lock obstruction of the right ventricle may move the air bubble in the ventricle and allow blood flow under the bubble.Hyperbaric therapy with 100% oxygen is recommended for patients presenting clinical features of arterial air embolism, as it accelerates removal of nitrogen from the bubbles by solution and improves tissue oxygenation. This is recommended particularly for cases of cardiopulmonary or neurological involvement. Early treatment has greatest benefits, but it can be effective as late as 30 hours after the injury.

Treatment of divers
Oxygen first aid treatment is useful for suspected gas embolism casualties or divers who have made fast ascents or missed decompression stops. Most fully closed-circuit rebreathers can deliver sustained high concentrations of oxygen-rich breathing gas and could be used as an alternative to pure open-circuit oxygen resuscitators. However pure oxygen from an oxygen cylinder through a Non-rebreather mask is the optimal way to deliver oxygen to a decompression illness patient.

Recompression is the most effective, though slow, treatment of gas embolism in divers. Normally this is carried out in a recompression chamber. As pressure increases, the solubility of a gas increases, which reduces bubble size by accelerating absorption of the gas into the surrounding blood and tissues.  Additionally, the volumes of the gas bubbles decrease in inverse proportion to the ambient pressure as described by Boyles law.  In the hyperbaric chamber the patient may breathe 100% oxygen, at ambient pressures up to a depth equivalent of 18 msw.  Under hyperbaric conditions, oxygen diffuses into the bubbles, displacing the nitrogen from the bubble and into solution in the blood.  Oxygen bubbles are more easily tolerated.  Diffusion of oxygen into the blood and tissues under hyperbaric conditions supports areas of the body which are deprived of blood flow when arteries are blocked by gas bubbles.  This helps to reduce ischemic injury </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is X-linked ichthyosis and can you explain it in depth? [/INST] X-linked ichthyosis (abbreviated XLI) is a skin condition caused by the hereditary deficiency of the steroid sulfatase (STS) enzyme that affects 1 in 2000 to 1 in 6000 males.  XLI manifests with dry, scaly skin and is due to deletions or mutations in the STS gene.  XLI can also occur in the context of larger deletions causing contiguous gene syndromes. Treatment is largely aimed at alleviating the skin symptoms. The term is from the Ancient Greek ichthys meaning fish.

Signs and symptoms
The major symptoms of XLI include scaling of the skin, particularly on the neck, trunk, and lower extremities.  The extensor surfaces are typically the most severely affected areas.  The >4 mm diameter scales adhere to the underlying skin and can be dark brown or gray in color.  Symptoms may subside during the summer.

Associated medical conditions
Aside from the skin scaling, XLI is not typically associated with other major medical problems. Atrial fibrillation or atrial flutter may affect up to 1 in 10 males with XLI. Heart rhythm abnormalities in individuals with XLI tend to co-occur with disorders of the gastrointestinal tract, and are likely to result from steroid sulfatase deficiency. Corneal opacities may be present but do not affect vision. Cryptorchidism is reported in some individuals. Individuals with XLI appear at increased risk of developmental disorders such as autism and Attention Deficit Hyperactivity Disorder and some affected individuals exhibit mood problems  Mood problems in XLI appear to be most influenced by stigma or bullying associated with the skin condition, and by difficulties with treating the skin condition. Individuals with XLI can exhibit intellectual disability, although this is thought to be due to deletions encompassing neighboring genes (e.g. VCX) in addition to STS.Female carriers generally do not experience any of these problems but can have difficulty during childbirth, as the STS expressed in the placenta plays a role in normal labor. Female carriers may also be at slightly increased risk of developing mental health problems following childbirth  For these reasons carriers should ensure their obstetrician is aware of the condition.

Genetics
The STS gene is located on the X chromosome at band Xp22.3.  Thus, the syndrome is an X-linked condition, and it affects males and females differently.  The 23rd pair of chromosomes is typically termed the "sex chromosomes".  Females have two X chromosomes and males have one X and one Y chromosome.  Therefore, in normal individuals, males carry a single copy of the STS gene and females carry two copies.  This gene partially escapes X-inactivation and females normally express higher amounts of the STS enzyme than males.XLI can occur through new deletions or mutations of the STS gene but is more commonly inherited from a carrier mother.  A hemizygous deletion or mutation of the STS gene in a male results in complete absence of enzyme activity, while a female carrier of a mutation or deletion is heterozygous and still has a normal copy of the STS gene.  Female carriers of an STS deletion or mutation still express the STS enzyme, although with decreased enzyme activity.For this reason, XLI most commonly affects males, although individuals with numeric abnormalities of the sex chromosomes (45,X and 47,XXY) who also carry STS deletions or mutations would be exceptions to this rule.In addition, a female could be affected if she were the offspring of an affected male and a carrier female and inherited a deletion or mutation of the STS gene on both X chromosomes.

Genetic counseling issues
Since the majority of cases appear to occur through transmission of an STS deletion from a carrier mother, enzyme testing or DNA testing should be performed in the mother of any newly diagnosed simplex case (i.e. the first case in a family).  In the case of an extended family with many affected individuals, carrier status can often be assigned based on pedigree analysis.

Males with XLI will transmit the X chromosome harboring the STS deletion or mutation to each of his female offspring, who will therefore be an obligate carrier.  However, all male offspring will be unaffected, since they receive their fathers Y chromosome.
Female carriers of an STS deletion or mutation have a 50% chance with each pregnancy of transmitting it to an offspring.  Thus, each male offspring has a 50% chance of being affected by XLI, while each female offspring has a 50% chance of being a carrier for this condition.  Any individual that inherits the mothers normal copy of the STS gene will be unaffected and will have an extremely low chance of having a child affected with this condition.Due to random segregation of the chromosomes during gametogenesis, each pregnancy will be subject to the same probabilities, regardless of the number of previously affected or unaffected offspring. The above recurrence risks are based on the assumption that an affected male or carrier female will have children with an unaffected or non-carrier individual.  The risks of having affected offspring would clearly increase in the case of a union between a male with XLI and a carrier female.

Physiology/biochemistry
The STS enzyme (EC 3.1.6.2), also referred to as Arylsulfatase C, is expressed throughout the body, with highest expression in the skin, liver, lymph nodes, and placenta, and lower expression in breast tissue and brain  STS catalyzes the hydrolysis of sulfated steroids, such as estrone sulfate and dehydroepiandrosterone sulfate (DHEAS), to non-sulfated steroids estradiol and androstenediol, respectively.  Prenatally, the enzyme is involved in placental estrogen production.  The enzyme is also involved in adrenal steroid production as well as conversion of sulfated steroids in other tissues.There seems to be a particularly important role for the enzyme in skin.  Deficiency of the enzyme leads to the characteristic dry and scaly skin seen in ichthyosis </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Electrocution and can you explain it in depth? [/INST] Electrocution is death or severe injury  caused by electric shock from electric current passing through the body. The word is derived from "electro" and "execution", but it is also used for accidental death.The term "electrocution" was coined in 1889 in the US just before the first use of the electric chair and originally referred to only electrical execution and not other electrical deaths. However, since no English word was available for non-judicial deaths due to electric shock, the word "electrocution" eventually took over as a description of all circumstances of electrical death from the new commercial electricity.

Origins
In the Netherlands in 1746 Pieter van Musschenbroeks lab assistant, Andreas Cuneus, received an extreme shock while working with a leyden jar, the first recorded injury from man-made electricity. By the mid-19th century high-voltage electrical systems came into use to power arc lighting for theatrical stage lighting and lighthouses leading to the first recorded accidental death in 1879 when a stage carpenter in Lyon, France, touched a 250-volt wire.The spread of arc light–based street lighting systems (which at the time ran at a voltage above 3,000 volts) after 1880 led to many people dying from coming in contact with these high-voltage lines, a strange new phenomenon which seemed to kill instantaneously without leaving a mark on the victim. This would lead to execution by electricity in the electric chair in the early 1890s as an official method of capital punishment in the U.S. state of New York, thought to be a more humane alternative to hanging. After an 1881 death in Buffalo, New York, caused by a high-voltage arc lighting system, Alfred P. Southwick sought to develop this phenomenon into a way to execute condemned criminals. Southwick, a dentist, based his device on the dental chair.The next nine years saw a promotion by Southwick, the New York state Gerry commission (which included Southwick) recommending execution by electricity, a June 4, 1888 law making it the state form of execution on January 2, 1889, and a further state committee of doctors and lawyers to finalize the details of the method used.The adoption of the electric chair became mixed up in the "war of currents" between Thomas Edisons direct current system and industrialist George Westinghouses alternating current system in 1889 when noted anti-AC activist Harold P. Brown became a consultant to the committee. Brown pushed, with the assistance and sometimes collusion of Edison Electric and Westinghouses chief AC rival, the Thomson-Houston Electric Company, for the successful adoption of alternating current to power the chair, an attempt to portray AC as a public menace and the "executioners current".

Etymology
In May 1889 the state of New York sentenced its first criminal, a street merchant named William Kemmler, to be executed in their new form of capital punishment. Tabloid newspapers, trying to describe this new form of electrical execution, started settling on "electrocution," a portmanteau word derived from "electro" and "execution". It was not the only choice of word people were considering. The New York Times editorial column noted words such as "Westinghoused" (after the Westinghouse Electric alternating current equipment that was to be used), "Gerrycide" (after Elbridge Thomas Gerry, who headed the New York death penalty commission that suggested adopting the electric chair), and "Browned" (after anti-AC activist Harold P. Brown). Thomas Edison preferred the words dynamort, ampermort and electromort. The New York Times hated the word electrocution, describing it as being pushed forward by "pretentious ignoramuses".

Medical aspects
Fish & Geddes state: "Contact with 20 mA of current can be fatal".The health hazard of an electric current flowing through the body depends on the amount of current and the length of time for which it flows, not merely on the voltage. However, a high voltage is required to produce a high current through the body. This is due to the relatively high resistance of skin when dry, requiring a high voltage to pass through </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Sedative and can you explain it in depth? [/INST] A sedative or tranquilliser is a substance that induces sedation by reducing irritability or excitement. They are CNS depressants and interact with brain activity causing its deceleration. Various kinds of sedatives can be distinguished, but the majority of them affect the neurotransmitter gamma-aminobutyric acid (GABA). In spite of the fact that each sedative acts in its own way, most produce relaxing effects by increasing GABA activity.This group is related to hypnotics. The term sedative describes drugs that serve to calm or relieve anxiety, whereas the term hypnotic describes drugs whose main purpose is to initiate, sustain, or lengthen sleep. Because these two functions frequently overlap, and because drugs in this class generally produce dose-dependent effects (ranging from anxiolysis to loss of consciousness) they are often referred to collectively as sedative-hypnotic drugs.Sedatives can be used to produce an overly-calming effect (alcohol being the most common sedating drug). In the event of an overdose or if combined with another sedative, many of these drugs can cause deep unconsciousness and even death.

Terminology
There is some overlap between the terms "sedative" and "hypnotic".
Advances in pharmacology have permitted more specific targeting of receptors, and greater selectivity of agents, which necessitates greater precision when describing these agents and their effects:

Anxiolytic refers specifically to the effect upon anxiety. (However, some benzodiazepines can be all three: sedatives, hypnotics, and anxiolytics).
Tranquilizer can refer to anxiolytics or antipsychotics.
Soporific and sleeping pill are near-synonyms for hypnotics.

The term "chemical cosh"
The term "chemical cosh" (a club) is sometimes used popularly for a strong sedative, particularly for:

widespread dispensation of antipsychotic drugs in residential care to make people with dementia easier to manage.
use of methylphenidate to calm children with attention deficit hyperactivity disorder, though paradoxically this drug is known to be a stimulant.
See also Antipsychotic controversy

Types of sedatives
Therapeutic use
Doctors and veterinarians often administer sedatives to patients in order to dull the patients anxiety related to painful or anxiety-provoking procedures. Although sedatives do not relieve pain in themselves, they can be a useful adjunct to analgesics in preparing patients for surgery, and are commonly given to patients before they are anaesthetized, or before other highly uncomfortable and  invasive procedures like cardiac catheterization, colonoscopy or MRI.

Risks
Sedative dependence
Some sedatives can cause psychological and physical dependence when taken regularly over a period of time, even at therapeutic doses. Dependent users may get withdrawal symptoms ranging from restlessness and insomnia to convulsions and death. When users become psychologically dependent, they feel as if they need the drug to function, although physical dependence does not necessarily occur, particularly with a short course of use. In both types of dependences, finding and using the sedative becomes the focus in life.  Both physical and psychological dependence can be treated with therapy.

Misuse
Many sedatives can be misused, but barbiturates and benzodiazepines are responsible for most of the problems with sedative use due to their widespread recreational or non-medical use. People who have difficulty dealing with stress, anxiety or sleeplessness may overuse or become dependent on sedatives. Some heroin users may take them either to supplement their drug or to substitute for it. Stimulant users may take sedatives to calm excessive jitteriness. Others take sedatives recreationally to relax and forget their worries. Barbiturate overdose is a factor in nearly one-third of all reported drug-related deaths. These include suicides and accidental drug poisonings. Accidental deaths sometimes occur when a drowsy, confused user repeats doses, or when sedatives are taken with alcohol.
A study from the United States found that in 2011, sedatives and hypnotics were a leading source of adverse drug events (ADEs) seen in the hospital setting: Approximately 2.8% of all ADEs present on admission and 4.4% of ADEs that originated during a hospital stay were caused by a sedative or hypnotic drug.  A second study noted that a total of 70,982 sedative exposures were reported to U.S. poison control centers in 1998, of which 2310 (3.2%) resulted in major toxicity and 89 (0.1%) resulted in death.  About half of all the people admitted to emergency rooms in the U.S. as a result of nonmedical use of sedatives have a legitimate prescription for the drug, but have taken an excessive dose or combined it with alcohol or other drugs.There are also serious paradoxical reactions that may occur in conjunction with the use of sedatives that lead to unexpected results in some individuals.  Malcolm Lader at the Institute of Psychiatry in London estimates the incidence of these adverse reactions at about 5%, even in short-term use of the drugs.   The paradoxical reactions may consist of depression, with or without suicidal tendencies, phobias, aggressiveness, violent behavior and symptoms sometimes misdiagnosed as psychosis.

Dangers of combining sedatives and alcohol
Sedatives and alcohol are sometimes combined recreationally or carelessly. Since alcohol is a strong  depressant that slows brain function and depresses respiration, the two substances compound each others actions and this combination can prove fatal.

Worsening of psychiatric symptoms
The long-term use of benzodiazepines may have a similar effect on the brain as alcohol, and are also implicated in depression, anxiety, posttraumatic stress disorder (PTSD), mania, psychosis, sleep disorders, sexual dysfunction, delirium, and neurocognitive disorders (including benzodiazepine-induced persisting dementia which persists even after the medications are stopped) </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Parapsoriasis and can you explain it in depth? [/INST]  </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Atrioventricular block and can you explain it in depth? [/INST] Atrioventricular block (AV block) is a type of heart block that occurs when the electrical signal traveling from the atria, or the upper chambers of the heart, to ventricles, or the lower chambers of the heart, is impaired. Normally, the sinoatrial node (SA node) produces an electrical signal to control the heart rate. The signal travels from the SA node to the ventricles through the atrioventricular node (AV node). In an AV block, this electrical signal is either delayed or completely blocked. When the signal is completely blocked, the ventricles produce their own electrical signal to control the heart rate. The heart rate produced by the ventricles is much slower than that produced by the SA node.Some AV blocks are benign, or normal, in certain people, such as in athletes or children. Other blocks are pathologic, or abnormal, and have several causes, including ischemia, infarction, fibrosis, and drugs.

Classification
There are three types, or degrees, of AV block: (1) first-degree, (2) second-degree, and (3) third-degree, with third-degree being the most severe. An ECG is used to differentiate between the different types of AV blocks. However, one important consideration when diagnosing AV blocks from ECGs is the possibility of pseudo- AV blocks which are due to concealed junctional extrasystoles. It is important to diagnose AV-blocks precisely because unnecessary pacemaker placement in patients with pseudo-AV blocks can worsen symptoms and create complications.

First-degree atrioventricular block
First-degree AV block occurs when there is a delay, but not disruption, as the electrical signal moves between the atrium and the ventricles through the AV node.  On ECG, this is defined by a PR interval greater than 200 msec. Additionally, there are no dropped, or skipped, beats.

Second-degree atrioventricular block
Second-degree AV block occurs when the electrical signal between the atria and ventricles is even more impaired than in a first-degree AV block. In a second-degree AV block, the impairment results in a failure to conduct an impulse, which causes a skipped beat.

Mobitz I
Mobitz I is characterized by a progressive yet reversible block of the AV node. On ECG, this is defined by progressive prolongation of the PR interval, with a resulting dropped beat (the PR interval gets longer and longer until a beat is finally dropped, or skipped).Some patients are asymptomatic; those who have symptoms respond to treatment effectively. There is a low risk of a Mobitz I AV block leading to heart attack and complete heart block.

Mobitz II
Mobitz II is caused by a sudden, unexpected failure of the His-Purkinje cells to conduct the electrical impulse. On ECG, the PR interval is unchanged from beat to beat, but there is a sudden failure to conduct the signal to the ventricles, and resulting in random skipped beat.The risks and possible effects of Mobitz II are much more severe than Mobitz I in that it can lead to severe heart attack.

Third-degree atrioventricular block
Third-degree AV block occurs when the signal between the atria and ventricles is completely blocked, and there is no communication between the two. None of the signals from the upper chambers makes it to the lower chambers. On ECG, there is no relationship between P waves and QRS complexes, meaning the P waves and QRS complexes are not in a 1:1 ratio.Third-degree AV block is the most severe of the AV blocks. Persons with third-degree AV block need emergency treatment including but not limited to a pacemaker.

Etiology
There are many causes of AV block, ranging from a normal variant among people to the result of a heart attack.First-degree AV block and Mobitz I second-degree block are often thought to be just normal, benign, conditions in people, and do not often result from a severe underlying condition.Mobitz II second-degree block and third-degree AV block are not normal variants and are associated with an underlying condition. Common causes include ischemia (lack of blood flow and oxygen to the heart muscle) or progressive fibrosis (excessive scaring) of the heart.  It is also possible that a high degree block can result after cardiac surgery during which the surgeon was in close proximity to the electrical conduction system and accidentally injured it. Reversible causes of Mobitz II and third-degree heart block include untreated Lyme disease, hypothyroidism, hyperkalemia (high levels of potassium), and drug toxicity. Drugs that slow the conduction of the electrical signal through AV node, such as beta-blockers, digoxin, calcium channel blockers, and amiodarone, can cause heart block if they are taken in excessive amounts, or the levels in the blood get too high.

Anatomy
The synchronized contraction of the heart occurs through a well-coordinated electrical signal pathway. The initial electrical signal originates from the SA node located in the upper portion of the right atrium. The electrical signal then travels through both the right and left atrium and causes the two atria to contract at the same time. This simultaneous contraction results in the P wave seen in an ECG tracing.The electrical signal then travels to the AV node located on the lower portion of the interatrial septum. At the AV node there is a delay in the electrical signal, which allows the atria to contract and blood to flow from the atria to the ventricles. This delay accounts for the ECG period between the P wave and the QRS complex, and creates the PR interval.
From the AV nodes, the electrical signal travels through Bundle of His and divides into the right bundle and left bundle, which are located within the interventricular septum. Finally, the electrical signal travels into the Purkinje fibers. The division of the signal into a right and left bundle and then into the Purkinje fibers allows for a simultaneous depolarization and contraction of the right and left ventricles. The contraction of the ventricles results in the QRS complex seen on an ECG tracing. After contraction, the ventricles must repolarize, or reset themselves, in order to allow for a second depolarization and contraction. The repolarization creates the T wave in the ECG tracing.

Diagnosis
An electrocardiogram, or ECG, is used to differentiate between the different types of AV block. In AV block, there is a disruption between the signal traveling from the atria to the ventricles </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Complication and can you explain it in depth? [/INST]  </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Ovarian disease and can you explain it in depth? [/INST] Ovarian diseases refer to diseases or disorders of the ovary.These can be classified as endocrine disorders or as a disorders of the reproductive system.
If the egg fails to release from the follicle in the ovary an ovarian cyst may form. Small ovarian cysts are common in healthy women. Some women have more follicles than usual (polycystic ovary syndrome), which inhibits the follicles to grow normally and this will cause cycle irregularities.
Various types of ovarian diseases exist. Some of the ovarian diseases or disorders include: endometriosis, ovarian cysts, ovarian epithelial cancer, ovarian germ cell tumors, ovarian low malignant potential tumors, and polycystic ovary syndrome (PCOS).

Endometriosis
Endometriosis is a condition in which tissues lining the uterus (endometrial stroma and gland) grows abnormally beyond the uterus that may become quite painful. In simpler terms, it means that the tissue lining the uterus develops in different parts outside of it. It can be either at ovary, fallopian tubes, or peritoneal spaces.There is no single cause of endometriosis.Symptoms:
Menstrual cramps, heavy menstrual bleeding, bowel or urinary problems, nausea, vomiting, blood with stools, painful intercourse, fatigues, spotting or bleeding between periods.Treatment:

Surgery at extreme situations
Hormonal treatments using birth controls.
Healthier lifestyle.

Ovarian cysts
It is common for many women to develop a cyst in their lifetime. At times, these can go unnoticed without pain or visible symptoms. A cyst may develop in either of the ovaries that are responsible for producing hormones and carrying eggs in the bodies of women. Ovarian cysts can be of various types like dermoid cysts, endometrioma cysts and the functional cyst being the most common one [1]
Symptoms:

Abdominal bloating or swelling.
Painful bowel movement.
Pelvic pain before or after the menstrual cycle.
Painful intercourse.
Pain in the lower back or thighs.
Breast tenderness.
Nausea and vomiting.
Fever.
Rapid breathing.
Faintness or dizziness.
Sharp pelvic pain.Treatment:

Taking of oral contraceptives or birth control pills as prescribed by the doctor.
Laparoscopy: Surgery to remove the cyst.
Hysterectomy in case the cyst is cancerous.

Ovarian epithelial cancer
It is one of the common ovarian cancers that affect women worldwide. It develops outside the ovaries and ultimately spreads outside and can affect other organs.
Causes:
It may happen if there is a family medical history of breast cancer, colon cancer, rectal cancer or uterine cancer, or Lynch syndrome </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Causality and can you explain it in depth? [/INST] Causality (also referred to as causation, or cause and effect) is influence by which one event, process, state, or object (a cause) contributes to the production of another event, process, state, or object (an effect) where the cause is partly responsible for the effect, and the effect is partly dependent on the cause. In general, a process has many causes, which are also said to be causal factors for it, and all lie in its past. An effect can in turn be a cause of, or causal factor for, many other effects, which all lie in its future. Some writers have held that causality is metaphysically prior to notions of time and space.Causality is an abstraction that indicates how the world progresses. As such a basic concept, it is more apt as an explanation of other concepts of progression than as something to be explained by others more basic. The concept is like those of agency and efficacy. For this reason, a leap of intuition may be needed to grasp it. Accordingly, causality is implicit in the logic and structure of ordinary language.In English studies of Aristotelian philosophy, the word "cause" is used as a specialized technical term, the translation of Aristotles term αἰτία, by which Aristotle meant "explanation" or "answer to a why question". Aristotle categorized the four types of answers as material, formal, efficient, and final "causes". In this case, the "cause" is the explanans for the explanandum, and failure to recognize that different kinds of "cause" are being considered can lead to futile debate. Of Aristotles four explanatory modes, the one nearest to the concerns of the present article is the "efficient" one.
David Hume, as part of his opposition to rationalism, argued that pure reason alone cannot prove the reality of efficient causality; instead, he appealed to custom and mental habit, observing that all human knowledge derives solely from experience.
The topic of causality remains a staple in contemporary philosophy.

Concept
Metaphysics
The nature of cause and effect is a concern of the subject known as metaphysics. Kant thought that time and space were notions prior to human understanding of the progress or evolution of the world, and he also recognized the priority of causality. But he did not have the understanding that came with knowledge of Minkowski geometry and the special theory of relativity, that the notion of causality can be used as a prior foundation from which to construct notions of time and space.

Ontology
A general metaphysical question about cause and effect is what kind of entity can be a cause, and what kind of entity can be an effect.
One viewpoint on this question is that cause and effect are of one and the same kind of entity, with causality an asymmetric relation between them. That is to say, it would make good sense grammatically to say either "A is the cause and B the effect" or "B is the cause and A the effect", though only one of those two can be actually true. In this view, one opinion, proposed as a metaphysical principle in process philosophy, is that every cause and every effect is respectively some process, event, becoming, or happening. An example is his tripping over the step was the cause, and his breaking his ankle the effect. Another view is that causes and effects are states of affairs, with the exact natures of those entities being less restrictively defined than in process philosophy.Another viewpoint on the question is the more classical one, that a cause and its effect can be of different kinds of entity. For example, in Aristotles efficient causal explanation, an action can be a cause while an enduring object is its effect. For example, the generative actions of his parents can be regarded as the efficient cause, with Socrates being the effect, Socrates being regarded as an enduring object, in philosophical tradition called a substance, as distinct from an action.

Epistemology
Since causality is a subtle metaphysical notion, considerable intellectual effort, along with exhibition of evidence, is needed to establish knowledge of it in particular empirical circumstances. According to David Hume, the human mind is unable to perceive causal relations directly. On this ground, the scholar distinguished between the regularity view on causality and the counterfactual notion. According to the counterfactual view, X causes Y if and only if, without X, Y would not exist. Hume interpreted the latter as an ontological view, i.e., as a description of the nature of causality but, given the limitations of the human mind, advised using the former (stating, roughly, that X causes Y if and only if the two events are spatiotemporally conjoined, and X precedes Y) as an epistemic definition of causality. Having an epistemic concept of causality is needed to distinguish between causal and noncausal relations. The contemporary philosophical literature on causality can be divided into five big approaches to causality. These include the (mentioned above) regularity, probabilistic, counterfactual, mechanistic, and manipulationist views. The five approaches can be shown to be reductive, i.e., define causality in terms of relations of other types. According to this reading, they define causality in terms of, respectively, empirical regularities (constant conjunctions of events), changes in conditional probabilities, counterfactual conditions, mechanisms underlying causal relations, and invariance under intervention.

Geometrical significance
Causality has the properties of antecedence and contiguity. These are topological, and are ingredients for space-time geometry. As developed by Alfred Robb, these properties allow the derivation of the notions of time and space. Max Jammer writes "the Einstein postulate ... opens the way to a straightforward construction of the causal topology ... of Minkowski space." Causal efficacy propagates no faster than light.Thus, the notion of causality is metaphysically prior to the notions of time and space. In practical terms, this is because use of the relation of causality is necessary for the interpretation of empirical experiments. Interpretation of experiments is needed to establish the physical and geometrical notions of time and space.

Volition
The deterministic world-view holds that the history of the universe can be exhaustively represented as a progression of events following one after as cause and effect. The incompatibilist version of this holds that there is no such thing as "free will". Compatibilism, on the other hand, holds that determinism is compatible with, or even necessary for, free will.

Necessary and sufficient causes
Causes may sometimes be distinguished into two types: necessary and sufficient. A third type of causation, which requires neither necessity nor sufficiency in and of itself, but which contributes to the effect, is called a "contributory cause".

Necessary causes
If x is a necessary cause of y, then the presence of y necessarily implies the prior occurrence of x. The presence of x, however, does not imply that y will occur.
Sufficient causes
If x is a sufficient cause of y, then the presence of x necessarily implies the subsequent occurrence of y. However, another cause z may alternatively cause y. Thus the presence of y does not imply the prior occurrence of x.
Contributory causes
For some specific effect, in a singular case, a factor that is a contributory cause is one among several co-occurrent causes. It is implicit that all of them are contributory. For the specific effect, in general, there is no implication that a contributory cause is necessary, though it may be so. In general, a factor that is a contributory cause is not sufficient, because it is by definition accompanied by other causes, which would not count as causes if it were sufficient. For the specific effect, a factor that is on some occasions a contributory cause might on some other occasions be sufficient, but on those other occasions it would not be merely contributory.J. L. Mackie argues that usual talk of "cause" in fact refers to INUS conditions (insufficient but non-redundant parts of a condition which is itself unnecessary but sufficient for the occurrence of the effect). An example is a short circuit as a cause for a house burning down. Consider the collection of events: the short circuit, the proximity of flammable material, and the absence of firefighters. Together these are unnecessary but sufficient to the houses burning down (since many other collections of events certainly could have led to the house burning down, for example shooting the house with a flamethrower in the presence of oxygen and so forth). Within this collection, the short circuit is an insufficient (since the short circuit by itself would not have caused the fire) but non-redundant (because the fire would not have happened without it, everything else being equal) part of a condition which is itself unnecessary but sufficient for the occurrence of the effect. So, the short circuit is an INUS condition for the occurrence of the house burning down.

Contrasted with conditionals
Conditional statements are not statements of causality. An important distinction is that statements of causality require the antecedent to precede or coincide with the consequent in time, whereas conditional statements do not require this temporal order. Confusion commonly arises since many different statements in English may be presented using "If ..., then ..." form (and, arguably, because this form is far more commonly used to make a statement of causality). The two types of statements are distinct, however.
For example, all of the following statements are true when interpreting "If ..., then ..." as the material conditional:

If Barack Obama is president of the United States in 2011, then Germany is in Europe.
If George Washington is president of the United States in 2011, then ⟨arbitrary statement⟩.The first is true since both the antecedent and the consequent are true. The second is true in sentential logic and indeterminate in natural language, regardless of the consequent statement that follows, because the antecedent is false.
The ordinary indicative conditional has somewhat more structure than the material conditional. For instance, although the first is the closest, neither of the preceding two statements seems true as an ordinary indicative reading. But the sentence:

If Shakespeare of Stratford-on-Avon did not write Macbeth, then someone else did.intuitively seems to be true, even though there is no straightforward causal relation in this hypothetical situation between Shakespeares not writing Macbeth and someone elses actually writing it.
Another sort of conditional, the counterfactual conditional, has a stronger connection with causality, yet even counterfactual statements are not all examples of causality. Consider the following two statements:

If A were a triangle, then A would have three sides.
If switch S were thrown, then bulb B would light.In the first case, it would not be correct to say that As being a triangle caused it to have three sides, since the relationship between triangularity and three-sidedness is that of definition. The property of having three sides actually determines As state as a triangle. Nonetheless, even when interpreted counterfactually, the first statement is true. An early version of Aristotles "four cause" theory is described as recognizing "essential cause". In this version of the theory, that the closed polygon has three sides is said to be the "essential cause" of its being a triangle. This use of the word cause is of course now far obsolete. Nevertheless, it is within the scope of ordinary language to say that it is essential to a triangle that it has three sides.
A full grasp of the concept of conditionals is important to understanding the literature on causality. In everyday language, loose conditional statements are often enough made, and need to be interpreted carefully.

Questionable cause
Fallacies of questionable cause, also known as causal fallacies, non-causa pro causa (Latin for "non-cause for cause"), or false cause, are informal fallacies where a cause is incorrectly identified.

Theories
Counterfactual theories
Counterfactual theories define causation in terms of a counterfactual relation. These theories can often be seeing as "floating" their account of causality on top of an account of the logic of counterfactual conditionals. This approach can be traced back to David Humes definition of the causal relation as that "where, if the first object had not been, the second never had existed." More full-fledged analysis of causation in terms of counterfactual conditionals only came in the 20th century after development of the possible world semantics for the evaluation of counterfactual conditionals. In his 1973 paper "Causation," David Lewis proposed the following definition of the notion of causal dependence:
An event E causally depends on C if, and only if, (i) if C had occurred, then E would have occurred, and (ii) if C had not occurred, then E would not have occurred.Causation is then defined as a chain of causal dependence. That is, C causes E if and only if there exists a sequence of events C, D1, D2, ... Dk, E such that each event in the sequence depends on the previous. This chain may be called a mechanism.
Note that the analysis does not purport to explain how we make causal judgements or how we reason about causation, but rather to give a metaphysical account of what it is for there to be a causal relation between some pair of events. If correct, the analysis has the power to explain certain features of causation. Knowing that causation is a matter of counterfactual dependence, we may reflect on the nature of counterfactual dependence to account for the nature of causation. For example, in his paper "Counterfactual Dependence and Times Arrow," Lewis sought to account for the time-directedness of counterfactual dependence in terms of the semantics of the counterfactual conditional. If correct, this theory can serve to explain a fundamental part of our experience, which is that we can only causally affect the future but not the past.

Probabilistic causation
Interpreting causation as a deterministic relation means that if A causes B, then A must always be followed by B. In this sense, war does not cause deaths, nor does smoking cause cancer or emphysema. As a result, many turn to a notion of probabilistic causation. Informally, A ("The person is a smoker") probabilistically causes B ("The person has now or will have cancer at some time in the future"), if the information that A occurred increases the likelihood of Bs occurrence. Formally, P{B|A}≥ P{B} where P{B|A} is the conditional probability that B will occur given the information that A occurred, and P{B} is the probability that B will occur having no knowledge whether A did or did not occur. This intuitive condition is not adequate as a definition for probabilistic causation because of its being too general and thus not meeting our intuitive notion of cause and effect. For example, if A denotes the event "The person is a smoker," B denotes the event "The person now has or will have cancer at some time in the future" and C denotes the event "The person now has or will have emphysema some time in the future," then the following three relationships hold: P{B|A} ≥ P{B}, P{C|A} ≥ P{C} and P{B|C} ≥ P{B}. The last relationship states that knowing that the person has emphysema increases the likelihood that he will have cancer. The reason for this is that having the information that the person has emphysema increases the likelihood that the person is a smoker, thus indirectly increasing the likelihood that the person will have cancer. However, we would not want to conclude that having emphysema causes cancer. Thus, we need additional conditions such as temporal relationship of A to B and a rational explanation as to the mechanism of action. It is hard to quantify this last requirement and thus different authors prefer somewhat different definitions.

Causal calculus
When experimental interventions are infeasible or illegal, the derivation of a cause-and-effect relationship from observational studies must rest on some qualitative theoretical assumptions, for example, that symptoms do not cause diseases, usually expressed in the form of missing arrows in causal graphs such as Bayesian networks or path diagrams. The theory underlying these derivations relies on the distinction between conditional probabilities, as in

        P
        (
        c
        a
        n
        c
        e
        r

          |

        s
        m
        o
        k
        i
        n
        g
        )

    {\displaystyle P(cancer|smoking)}
  , and interventional probabilities, as in

        P
        (
        c
        a
        n
        c
        e
        r

          |

        d
        o
        (
        s
        m
        o
        k
        i
        n
        g
        )
        )

    {\displaystyle P(cancer|do(smoking))}
  . The former reads: "the probability of finding cancer in a person known to smoke, having started, unforced by the experimenter, to do so at an unspecified time in the past", while the latter reads: "the probability of finding cancer in a person forced by the experimenter to smoke at a specified time in the past". The former is a statistical notion that can be estimated by observation with negligible intervention by the experimenter, while the latter is a causal notion which is estimated in an experiment with an important controlled randomized intervention. It is specifically characteristic of quantal phenomena that observations defined by incompatible variables always involve important intervention by the experimenter, as described quantitatively by the observer effect. In classical thermodynamics, processes are initiated by interventions called thermodynamic operations. In other branches of science, for example astronomy, the experimenter can often observe with negligible intervention.
The theory of "causal calculus" (also known as do-calculus, Judea Pearls Causal Calculus, Calculus of
Actions) permits one to infer interventional probabilities from conditional probabilities in causal Bayesian networks with unmeasured variables. One very practical result of this theory is the characterization of confounding variables, namely, a sufficient set of variables that, if adjusted for, would yield the correct causal effect between variables of interest. It can be shown that a sufficient set for estimating the causal effect of

        X

    {\displaystyle X}
   on

        Y

    {\displaystyle Y}
   is any set of non-descendants of

        X

    {\displaystyle X}
   that

        d

    {\displaystyle d}
  -separate

        X

    {\displaystyle X}
   from

        Y

    {\displaystyle Y}
   after removing all arrows emanating from

        X

    {\displaystyle X}
  . This criterion, called "backdoor", provides a mathematical definition of "confounding" and helps researchers identify accessible sets of variables worthy of measurement.

Structure learning
While derivations in causal calculus rely on the structure of the causal graph, parts of the causal structure can, under certain assumptions, be learned from statistical data. The basic idea goes back to Sewall Wrights 1921 work on path analysis. A "recovery" algorithm was developed by Rebane and Pearl (1987) which rests on Wrights distinction between the three possible types of causal substructures allowed in a directed acyclic graph (DAG):

        X
        →
        Y
        →
        Z

    {\displaystyle X\rightarrow Y\rightarrow Z}

        X
        ←
        Y
        →
        Z

    {\displaystyle X\leftarrow Y\rightarrow Z}

        X
        →
        Y
        ←
        Z

    {\displaystyle X\rightarrow Y\leftarrow Z}
  Type 1 and type 2 represent the same statistical dependencies (i.e.,

        X

    {\displaystyle X}
   and

        Z

    {\displaystyle Z}
   are independent given

        Y

    {\displaystyle Y}
  ) and are, therefore, indistinguishable within purely cross-sectional data. Type 3, however, can be uniquely identified, since

        X

    {\displaystyle X}
   and

        Z

    {\displaystyle Z}
   are marginally independent and all other pairs are dependent. Thus, while the skeletons (the graphs stripped of arrows) of these three triplets are identical, the directionality of the arrows is partially identifiable. The same distinction applies when

        X

    {\displaystyle X}
   and

        Z

    {\displaystyle Z}
   have common ancestors, except that one must first condition on those ancestors. Algorithms have been developed to systematically determine the skeleton of the underlying graph and, then, orient all arrows whose directionality is dictated by the conditional independencies observed.Alternative methods of structure learning search through the many possible causal structures among the variables, and remove ones which are strongly incompatible with the observed correlations. In general this leaves a set of possible causal relations, which should then be tested by analyzing time series data or, preferably, designing appropriately controlled experiments. In contrast with Bayesian Networks, path analysis (and its generalization, structural equation modeling), serve better to estimate a known causal effect or to test a causal model than to generate causal hypotheses.
For nonexperimental data, causal direction can often be inferred if information about time is available. This is because (according to many, though not all, theories) causes must precede their effects temporally. This can be determined by statistical time series models, for instance, or with a statistical test based on the idea of Granger causality, or by direct experimental manipulation. The use of temporal data can permit statistical tests of a pre-existing theory of causal direction. For instance, our degree of confidence in the direction and nature of causality is much greater when supported by cross-correlations, ARIMA models, or cross-spectral analysis using vector time series data than by cross-sectional data.

Derivation theories
Nobel laureate Herbert A. Simon and philosopher Nicholas Rescher claim that the asymmetry of the causal relation is unrelated to the asymmetry of any mode of implication that contraposes. Rather, a causal relation is not a relation between values of variables, but a function of one variable (the cause) on to another (the effect). So, given a system of equations, and a set of variables appearing in these equations, we can introduce an asymmetric relation among individual equations and variables that corresponds perfectly to our commonsense notion of a causal ordering. The system of equations must have certain properties, most importantly, if some values are chosen arbitrarily, the remaining values will be determined uniquely through a path of serial discovery that is perfectly causal. They postulate the inherent serialization of such a system of equations may correctly capture causation in all empirical fields, including physics and economics.

Manipulation theories
Some theorists have equated causality with manipulability. Under these theories, x causes y only in the case that one can change x in order to change y. This coincides with commonsense notions of causations, since often we ask causal questions in order to change some feature of the world. For instance, we are interested in knowing the causes of crime so that we might find ways of reducing it.
These theories have been criticized on two primary grounds. First, theorists complain that these accounts are circular. Attempting to reduce causal claims to manipulation requires that manipulation is more basic than causal interaction. But describing manipulations in non-causal terms has provided a substantial difficulty.
The second criticism centers around concerns of anthropocentrism. It seems to many people that causality is some existing relationship in the world that we can harness for our desires. If causality is identified with our manipulation, then this intuition is lost. In this sense, it makes humans overly central to interactions in the world.
Some attempts to defend manipulability theories are recent accounts that do not claim to reduce causality to manipulation. These accounts use manipulation as a sign or feature in causation without claiming that manipulation is more fundamental than causation.

Process theories
Some theorists are interested in distinguishing between causal processes and non-causal processes (Russell 1948; Salmon 1984). These theorists often want to distinguish between a process and a pseudo-process. As an example, a ball moving through the air (a process) is contrasted with the motion of a shadow (a pseudo-process). The former is causal in nature while the latter is not.
Salmon (1984) claims that causal processes can be identified by their ability to transmit an alteration over space and time. An alteration of the ball (a mark by a pen, perhaps) is carried with it as the ball goes through the air. On the other hand, an alteration of the shadow (insofar as it is possible) will not be transmitted by the shadow as it moves along.
These theorists claim that the important concept for understanding causality is not causal relationships or causal interactions, but rather identifying causal processes. The former notions can then be defined in terms of causal processes.

A subgroup of the process theories is the mechanistic view on causality. It states that that causal relations supervene on mechanisms. While the notion of mechanism is understood differently, the definition put forward by the group of philosophers referred to as the New Mechanists dominate the literature.

Fields
Science
For the scientific investigation of efficient causality, the cause and effect are each best conceived of as temporally transient processes.
Within the conceptual frame of the scientific method, an investigator sets up several distinct and contrasting temporally transient material processes that have the structure of experiments, and records candidate material responses, normally intending to determine causality in the physical world. For instance, one may want to know whether a high intake of carrots causes humans to develop the bubonic plague. The quantity of carrot intake is a process that is varied from occasion to occasion. The occurrence or non-occurrence of subsequent bubonic plague is recorded. To establish causality, the experiment must fulfill certain criteria, only one example of which is mentioned here. For example, instances of the hypothesized cause must be set up to occur at a time when the hypothesized effect is relatively unlikely in the absence of the hypothesized cause; such unlikelihood is to be established by empirical evidence. A mere observation of a correlation is not nearly adequate to establish causality. In nearly all cases, establishment of causality relies on repetition of experiments and probabilistic reasoning. Hardly ever is causality established more firmly than as more or less probable. It is most convenient for establishment of causality if the contrasting material states of affairs are precisely matched, except for only one variable factor, perhaps measured by a real number.

Physics
One has to be careful in the use of the word cause in physics. Properly speaking, the hypothesized cause and the hypothesized effect are each temporally transient processes. For example, force is a useful concept for the explanation of acceleration, but force is not by itself a cause. More is needed. For example, a temporally transient process might be characterized by a definite change of force at a definite time. Such a process can be regarded as a cause. Causality is not inherently implied in equations of motion, but postulated as an additional constraint that needs to be satisfied (i.e. a cause always precedes its effect). This constraint has mathematical implications such as the Kramers-Kronig relations.
Causality is one of the most fundamental and essential notions of physics. Causal efficacy cannot propagate faster than light. Otherwise, reference coordinate systems could be constructed (using the Lorentz transform of special relativity) in which an observer would see an effect precede its cause (i.e. the postulate of causality would be violated).
Causal notions appear in the context of the flow of mass-energy. Any actual process has causal efficacy that can propagate no faster than light. In contrast, an abstraction has no causal efficacy. Its mathematical expression does not propagate in the ordinary sense of the word, though it may refer to virtual or nominal velocities with magnitudes greater than that of light. For example, wave packets are mathematical objects that have group velocity and phase velocity. The energy of a wave packet travels at the group velocity (under normal circumstances); since energy has causal efficacy, the group velocity cannot be faster than the speed of light. The phase of a wave packet travels at the phase velocity; since phase is not causal, the phase velocity of a wave packet can be faster than light.Causal notions are important in general relativity to the extent that the existence of an arrow of time demands that the universes semi-Riemannian manifold be orientable, so that "future" and "past" are globally definable quantities.

Engineering
A causal system is a system with output and internal states that depends only on the current and previous input values. A system that has some dependence on input values from the future (in addition to possible past or current input values) is termed an acausal system, and a system that depends solely on future input values is an anticausal system. Acausal filters, for example, can only exist as postprocessing filters, because these filters can extract future values from a memory buffer or a file.

Biology, medicine and epidemiology
Austin Bradford Hill built upon the work of Hume and Popper and suggested in his paper "The Environment and Disease: Association or Causation?" that aspects of an association such as strength, consistency, specificity, and temporality be considered in attempting to distinguish causal from noncausal associations in the epidemiological situation. (See Bradford-Hill criteria.) He did not note however, that temporality is the only necessary criterion among those aspects. Directed acyclic graphs (DAGs) are increasingly used in epidemiology to help enlighten causal thinking.

Psychology
Psychologists take an empirical approach to causality, investigating how people and non-human animals detect or infer causation from sensory information, prior experience and innate knowledge.

AttributionAttribution theory is the theory concerning how people explain individual occurrences of causation. Attribution can be external (assigning causality to an outside agent or force—claiming that some outside thing motivated the event) or internal (assigning causality to factors within the person—taking personal responsibility or accountability for ones actions and claiming that the person was directly responsible for the event). Taking causation one step further, the type of attribution a person provides influences their future behavior.
The intention behind the cause or the effect can be covered by the subject of action. See also accident; blame; intent; and responsibility.

Causal powersWhereas David Hume argued that causes are inferred from non-causal observations, Immanuel Kant claimed that people have innate assumptions about causes. Within psychology, Patricia Cheng attempted to reconcile the Humean and Kantian views. According to her power PC theory, people filter observations of events through an intuition that causes have the power to generate (or prevent) their effects, thereby inferring specific cause-effect relations.

Causation and salienceOur view of causation depends on what we consider to be the relevant events. Another way to view the statement, "Lightning causes thunder" is to see both lightning and thunder as two perceptions of the same event, viz., an electric discharge that we perceive first visually and then aurally.

Naming and causalityDavid Sobel and Alison Gopnik from the Psychology Department of UC Berkeley designed a device known as the blicket detector which would turn on when an object was placed on it. Their research suggests that "even young children will easily and swiftly learn about a new causal power of an object and spontaneously use that information in classifying and naming the object."
Perception of launching eventsSome researchers such as Anjan Chatterjee at the University of Pennsylvania and Jonathan Fugelsang at the University of Waterloo are using neuroscience techniques to investigate the neural and psychological underpinnings of causal launching events in which one object causes another object to move. Both temporal and spatial factors can be manipulated.See Causal Reasoning (Psychology) for more information.

Statistics and economics
Statistics and economics usually employ pre-existing data or experimental data to infer causality by regression methods. The body of statistical techniques involves substantial use of regression analysis. Typically a linear relationship such as

          y

            i

        =

          a

            0

        +

          a

            1

          x

            1
            ,
            i

        +

          a

            2

          x

            2
            ,
            i

        +
        ⋯
        +

          a

            k

          x

            k
            ,
            i

        +

          e

            i

    {\displaystyle y_{i}=a_{0}+a_{1}x_{1,i}+a_{2}x_{2,i}+\dots +a_{k}x_{k,i}+e_{i}}
  is postulated, in which

          y

            i

    {\displaystyle y_{i}}
   is the ith observation of the dependent variable (hypothesized to be the caused variable),

          x

            j
            ,
            i

    {\displaystyle x_{j,i}}
   for j=1,...,k is the ith observation on the jth independent variable (hypothesized to be a causative variable), and

          e

            i

    {\displaystyle e_{i}}
   is the error term for the ith observation (containing the combined effects of all other causative variables, which must be uncorrelated with the included independent variables). If there is reason to believe that none of the

          x

            j

    {\displaystyle x_{j}}
  s is caused by y, then estimates of the coefficients

          a

            j

    {\displaystyle a_{j}}
   are obtained. If the null hypothesis that

          a

            j

        =
        0

    {\displaystyle a_{j}=0}
   is rejected, then the alternative hypothesis that

          a

            j

        ≠
        0

    {\displaystyle a_{j}\neq 0}
   and equivalently that

          x

            j

    {\displaystyle x_{j}}
   causes y cannot be rejected. On the other hand, if the null hypothesis that

          a

            j

        =
        0

    {\displaystyle a_{j}=0}
   cannot be rejected, then equivalently the hypothesis of no causal effect of

          x

            j

    {\displaystyle x_{j}}
   on y cannot be rejected. Here the notion of causality is one of contributory causality as discussed above: If the true value

          a

            j

        ≠
        0

    {\displaystyle a_{j}\neq 0}
  , then a change in

          x

            j

    {\displaystyle x_{j}}
   will result in a change in y unless some other causative variable(s), either included in the regression or implicit in the error term, change in such a way as to exactly offset its effect; thus a change in

          x

            j

    {\displaystyle x_{j}}
   is not sufficient to change y. Likewise, a change in

          x

            j

    {\displaystyle x_{j}}
   is not necessary to change y, because a change in y could be caused by something implicit in the error term (or by some other causative explanatory variable included in the model).
The above way of testing for causality requires belief that there is no reverse causation, in which y would cause

          x

            j

    {\displaystyle x_{j}}
  . This belief can be established in one of several ways. First, the variable

          x

            j

    {\displaystyle x_{j}}
   may be a non-economic variable: for example, if rainfall amount

          x

            j

    {\displaystyle x_{j}}
   is hypothesized to affect the futures price y of some agricultural commodity, it is impossible that in fact the futures price affects rainfall amount (provided that cloud seeding is never attempted). Second, the instrumental variables technique may be employed to remove any reverse causation by introducing a role for other variables (instruments) that are known to be unaffected by the dependent variable. Third, the principle that effects cannot precede causes can be invoked, by including on the right side of the regression only variables that precede in time the dependent variable; this principle is invoked, for example, in testing for Granger causality and in its multivariate analog, vector autoregression, both of which control for lagged values of the dependent variable while testing for causal effects of lagged independent variables.
Regression analysis controls for other relevant variables by including them as regressors (explanatory variables). This helps to avoid false inferences of causality due to the presence of a third, underlying, variable that influences both the potentially causative variable and the potentially caused variable: its effect on the potentially caused variable is captured by directly including it in the regression, so that effect will not be picked up as an indirect effect through the potentially causative variable of interest. Given the above procedures, coincidental (as opposed to causal) correlation can be probabilistically rejected if data samples are large and if regression results pass cross-validation tests showing that the correlations hold even for data that were not used in the regression. Asserting with certitude that a common-cause is absent and the regression represents the true causal structure is in principle impossible.Apart from constructing statistical models of observational and experimental data, economists use axiomatic (mathematical) models to infer and represent causal mechanisms. Highly abstract theoretical models that isolate and idealize one mechanism dominate microeconomics. In macroeconomics, economists use broad mathematical models that are calibrated on historical data. A subgroup of calibrated models, dynamic stochastic general equilibrium (DSGE) models are employed to represent (in a simplified way) the whole economy and simulate changes in fiscal and monetary policy.

Management
For quality control in manufacturing in the 1960s, Kaoru Ishikawa developed a cause and effect diagram, known as an Ishikawa diagram or fishbone diagram. The diagram categorizes causes, such as into the six main categories shown here. These categories are then sub-divided. Ishikawas method identifies "causes" in brainstorming sessions conducted among various groups involved in the manufacturing process. These groups can then be labeled as categories in the diagrams. The use of these diagrams has now spread beyond quality control, and they are used in other areas of management and in design and engineering. Ishikawa diagrams have been criticized for failing to make the distinction between necessary conditions and sufficient conditions. It seems that Ishikawa was not even aware of this distinction.

Humanities
History
In the discussion of history, events are sometimes considered as if in some way being agents that can then bring about other historical events. Thus, the combination of poor harvests, the hardships of the peasants, high taxes, lack of representation of the people, and kingly ineptitude are among the causes of the French Revolution. This is a somewhat Platonic and Hegelian view that reifies causes as ontological entities. In Aristotelian terminology, this use approximates to the case of the efficient cause.
Some philosophers of history such as Arthur Danto have claimed that "explanations in history and elsewhere" describe "not simply an event—something that happens—but a change". Like many practicing historians, they treat causes as intersecting actions and sets of actions which bring about "larger changes", in Dantos words: to decide "what are the elements which persist through a change" is "rather simple" when treating an individuals "shift in attitude", but "it is considerably more complex and metaphysically challenging when we are interested in such a change as, say, the break-up of feudalism or the emergence of nationalism".Much of the historical debate about causes has focused on the relationship between communicative and other actions, between singular and repeated ones, and between actions, structures of action or group and institutional contexts and wider sets of conditions. John Gaddis has distinguished between exceptional and general causes (following Marc Bloch) and between "routine" and "distinctive links" in causal relationships: "in accounting for what happened at Hiroshima on August 6, 1945, we attach greater importance to the fact that President Truman ordered the dropping of an atomic bomb than to the decision of the Army Air Force to carry out his orders." He has also pointed to the difference between immediate, intermediate and distant causes. For his part, Christopher Lloyd puts forward four "general concepts of causation" used in history: the "metaphysical idealist concept, which asserts that the phenomena of the universe are products of or emanations from an omnipotent being or such final cause"; "the empiricist (or Humean) regularity concept, which is based on the idea of causation being a matter of constant conjunctions of events"; "the functional/teleological/consequential concept", which is "goal-directed, so that goals are causes"; and the "realist, structurist and dispositional approach, which sees relational structures and internal dispositions as the causes of phenomena".

Law
According to law and jurisprudence, legal cause must be demonstrated to hold a defendant liable for a crime or a tort (i.e. a civil wrong such as negligence or trespass). It must be proven that causality, or a "sufficient causal link" relates the defendants actions to the criminal event or damage in question. Causation is also an essential legal element that must be proven to qualify for remedy measures under international trade law.

History
Hindu philosophy
Vedic period (c. 1750–500 BCE) literature has karmas Eastern origins. Karma is the belief held by Sanatana Dharma and major religions that a persons actions cause certain effects in the current life and/or in future life, positively or negatively. The various philosophical schools (darshanas) provide different accounts of the subject. The doctrine of satkaryavada affirms that the effect inheres in the cause in some way. The effect is thus either a real or apparent modification of the cause. The doctrine of asatkaryavada affirms that the effect does not inhere in the cause, but is a new arising. See Nyaya for some details of the theory of causation in the Nyaya school. In Brahma Samhita, Brahma describes Krishna as the prime cause of all causes.Bhagavad-gītā 18.14 identifies five causes for any action (knowing which it can be perfected): the body, the individual soul, the senses, the efforts and the supersoul.
According to Monier-Williams, in the Nyāya causation theory from Sutra I.2.I,2 in the Vaisheshika philosophy, from causal non-existence is effectual non-existence; but, not effectual non-existence from causal non-existence. A cause precedes an effect. With a threads and cloth metaphors, three causes are:

Co-inherence cause: resulting from substantial contact, substantial causes, threads are substantial to cloth, corresponding to Aristotles material cause.
Non-substantial cause: Methods putting threads into cloth, corresponding to Aristotles formal cause.
Instrumental cause: Tools to make the cloth, corresponding to Aristotles efficient cause.Monier-Williams also proposed that Aristotles and the Nyayas causality are considered conditional aggregates necessary to mans productive work.

Buddhist philosophy
Karma is the causality principle focusing on 1) causes, 2) actions, 3) effects, where it is the minds phenomena that guide the actions that the actor performs. Buddhism trains the actors actions for continued and uncontrived virtuous outcomes aimed at reducing suffering. This follows the Subject–verb–object structure.The general or universal definition of pratityasamutpada (or "dependent origination" or "dependent arising" or "interdependent co-arising") is that everything arises in dependence upon multiple causes and conditions; nothing exists as a singular, independent entity. A traditional example in Buddhist texts is of three sticks standing upright and leaning against each other and supporting each other. If one stick is taken away, the other two will fall to the ground.Causality in the Chittamatrin Buddhist school approach, Asangas (c. 400 CE) mind-only Buddhist school, asserts that objects cause consciousness in the minds image. Because causes precede effects, which must be different entities, then subject and object are different. For this school, there are no objects which are entities external to a perceiving consciousness. The Chittamatrin and the Yogachara Svatantrika schools accept that there are no objects external to the observers causality. This largely follows the Nikayas approach.The Vaibhashika (c. 500 CE) is an early Buddhist school which favors direct object contact and accepts simultaneous cause and effects. This is based in the consciousness example which says, intentions and feelings are mutually accompanying mental factors that support each other like poles in tripod. In contrast, simultaneous cause and effect rejectors say that if the effect already exists, then it cannot effect the same way again. How past, present and future are accepted is a basis for various Buddhist schools causality viewpoints.All the classic Buddhist schools teach karma. "The law of karma is a special instance of the law of cause and effect, according to which all our actions of body, speech, and mind are causes and all our experiences are their effects."

Western philosophy
Aristotelian
Aristotle identified four kinds of answer or explanatory mode to various "Why?" questions. He thought that, for any given topic, all four kinds of explanatory mode were important, each in its own right. As a result of traditional specialized philosophical peculiarities of language, with translations between ancient Greek, Latin, and English, the word cause is nowadays in specialized philosophical writings used to label Aristotles four kinds. In ordinary language, the word cause has a variety of meanings, the most common of which refers to efficient causation, which is the topic of the present article.

Material cause, the material whence a thing has come or that which persists while it changes, as for example, ones mother or the bronze of a statue (see also substance theory).
Formal cause, whereby a things dynamic form or static shape determines the things properties and function, as a human differs from a statue of a human or as a statue differs from a lump of bronze.
Efficient cause, which imparts the first relevant movement, as a human lifts a rock or raises a statue. This is the main topic of the present article.
Final cause, the criterion of completion, or the end; it may refer to an action or to an inanimate process. Examples: Socrates takes a walk after dinner for the sake of his health; earth falls to the lowest level because that is its nature.Of Aristotles four kinds or explanatory modes, only one, the efficient cause is a cause as defined in the leading paragraph of this present article. The other three explanatory modes might be rendered material composition, structure and dynamics, and, again, criterion of completion. The word that Aristotle used was αἰτία. For the present purpose, that Greek word would be better translated as "explanation" than as "cause" as those words are most often used in current English. Another translation of Aristotle is that he meant "the four Becauses" as four kinds of answer to "why" questions.Aristotle assumed efficient causality as referring to a basic fact of experience, not explicable by, or reducible to, anything more fundamental or basic.
In some works of Aristotle, the four causes are listed as (1) the essential cause, (2) the logical ground, (3) the moving cause, and (4) the final cause. In this listing, a statement of essential cause is a demonstration that an indicated object conforms to a definition of the word that refers to it. A statement of logical ground is an argument as to why an object statement is true. These are further examples of the idea that a "cause" in general in the context of Aristotles usage is an "explanation".The word "efficient" used here can also be translated from Aristotle as "moving" or "initiating".Efficient causation was connected with Aristotelian physics, which recognized the four elements (earth, air, fire, water), and added the fifth element (aether). Water and earth by their intrinsic property gravitas or heaviness intrinsically fall toward, whereas air and fire by their intrinsic property levitas or lightness intrinsically rise away from, Earths center—the motionless center of the universe—in a straight line while accelerating during the substances approach to its natural place.
As air remained on Earth, however, and did not escape Earth while eventually achieving infinite speed—an absurdity—Aristotle inferred that the universe is finite in size and contains an invisible substance that held planet Earth and its atmosphere, the sublunary sphere, centered in the universe. And since celestial bodies exhibit perpetual, unaccelerated motion orbiting planet Earth in unchanging relations, Aristotle inferred that the fifth element, aither, that fills space and composes celestial bodies intrinsically moves in perpetual circles, the only constant motion between two points. (An object traveling a straight line from point A to B and back must stop at either point before returning to the other.)
Left to itself, a thing exhibits natural motion, but can—according to Aristotelian metaphysics—exhibit enforced motion imparted by an efficient cause. The form of plants endows plants with the processes nutrition and reproduction, the form of animals adds locomotion, and the form of humankind adds reason atop these. A rock normally exhibits natural motion—explained by the rocks material cause of being composed of the element earth—but a living thing can lift the rock, an enforced motion diverting the rock from its natural place and natural motion. As a further kind of explanation, Aristotle identified the final cause, specifying a purpose or criterion of completion in light of which something should be understood.
Aristotle himself explained,

Cause means
(a) in one sense, that as the result of whose presence something comes into being—e.g., the bronze of a statue and the silver of a cup, and the classes which contain these [i.e., the material cause];
(b) in another sense, the form or pattern; that is, the essential formula and the classes which contain it—e.g. the ratio 2:1 and number in general is the cause of the octave—and the parts of the formula [i.e., the formal cause].
(c) The source of the first beginning of change or rest; e.g. the man who plans is a cause, and the father is the cause of the child, and in general that which produces is the cause of that which is produced, and that which changes of that which is changed [i.e., the efficient cause].
(d) The same as "end"; i.e. the final cause; e.g., as the "end" of walking is health. For why does a man walk? "To be healthy", we say, and by saying this we consider that we have supplied the cause [the final cause].

(e) All those means towards the end which arise at the instigation of something else, as, e.g., fat-reducing, purging, drugs, and instruments are causes of health; for they all have the end as their object, although they differ from each other as being some instruments, others actions [i.e., necessary conditions].
Aristotle further discerned two modes of causation: proper (prior) causation and accidental (chance) causation. All causes, proper and accidental, can be spoken as potential or as actual, particular or generic. The same language refers to the effects of causes, so that generic effects are assigned to generic causes, particular effects to particular causes, and actual effects to operating causes.
Averting infinite regress, Aristotle inferred the first mover—an unmoved mover. The first movers motion, too, must have been caused, but, being an unmoved mover, must have moved only toward a particular goal or desire.

Pyrrhonism
While the plausibility of causality was accepted in Pyrrhonism, it was equally accepted that it was plausible that nothing was the cause of anything.

Middle Ages
In line with Aristotelian cosmology, Thomas Aquinas posed a hierarchy prioritizing Aristotles four causes: "final > efficient > material > formal". Aquinas sought to identify the first efficient cause—now simply first cause—as everyone would agree, said Aquinas, to call it God. Later in the Middle Ages, many scholars conceded that the first cause was God, but explained that many earthly events occur within Gods design or plan, and thereby scholars sought freedom to investigate the numerous secondary causes.

After the Middle Ages
For Aristotelian philosophy before Aquinas, the word cause had a broad meaning. It meant answer to a why question or explanation, and Aristotelian scholars recognized four kinds of such answers. With the end of the Middle Ages, in many philosophical usages, the meaning of the word cause narrowed. It often lost that broad meaning, and was restricted to just one of the four kinds. For authors such as Niccolò Machiavelli, in the field of political thinking, and Francis Bacon, concerning science more generally, Aristotles moving cause was the focus of their interest. A widely used modern definition of causality in this newly narrowed sense was assumed by David Hume </s>