High Flow Nasal Cannula (HFNC)
March 2, 2018
HFNC is the delivery of humidified and heated oxygen at flow rates up to 60L/minute. It is an alternative to intubation or noninvasive positive-pressure ventilation. See additional content below on HFNC.
Airway management is a critical need in many acutely ill and injured patients. Optimal strategies seek to assist with airway patency, oxygen delivery, and carbon dioxide excretion. Commonly, many classify airway management techniques into two categories: noninvasive (passive oxygenation, bag-valve mask ventilation, supraglottic airways, and noninvasive positive-pressure ventilation) and invasive (endotracheal intubation, cricothyroidotomy, transcutaneous needle jet ventilation, and tracheostomy). This chapter discusses noninvasive airway management strategies. Detailed discussion of invasive airway management strategies is found in the chapters 29, Intubation and Mechanical Ventilation and chapter 111, Intubation and Ventilation in Infants and Children.
ASSESSMENT OF THE AIRWAY AND VENTILATORY EFFORT
The decision to initiate airway support must often be made rapidly based on the patient's clinical condition. Laboratory testing or other studies should not delay the decision to initiate airway management strategies.
First, assess every patient for airway obstruction, which can be functional (e.g., unconscious patient) or mechanical (e.g., foreign body). The ability to spontaneously swallow and speak provides a basic indication of airway patency, and the absence is a potential sign of obstruction. Other potential signs of airway obstruction include anxiety, wheezing or stridor, and coughing. Many conditions can cause airway obstruction (Table 28–1).
Causes of Upper Airway Obstruction
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Causes of Upper Airway Obstruction
|Congenital/Genetic ||Infectious ||Medical ||Trauma/Tumor |
|Large tonsils ||Tonsillitis ||Cystic fibrosis ||Laryngeal trauma |
|Macroglossia ||Peritonsillar abscess ||Angioedema ||Hematoma/masses |
|Micrognathia ||Pretracheal abscess ||Laryngospasm ||Smoke inhalation |
|Neck masses ||Epiglottitis ||Inflammatory ||Thermal injuries |
|Large adenoids || |
Laryngitis/respiratory syncytial virus
|Airway muscle relaxation ||Foreign body/hemorrhage |
Some obstructions, such as foreign bodies or masses, are subglottic, or below the vocal cords.
Laryngospasm is obstructive closure of the glottis by constriction of laryngeal muscles. Laryngospasm may result from stimulation of the upper airway receptors on the tongue, palate, and oropharynx. Other causes include chemical irritation, secretions, blood, water, and vomitus in the upper airway and traction on the pelvic/abdominal viscera. Laryngospasm can persist after the causative stimulus has departed.
SIGNS AND SYMPTOMS OF RESPIRATORY FAILURE
Patients with hypoventilation (inadequate carbon dioxide excretion) and hypoxia (inadequate alveolar oxygen content) can present with a variety of symptoms including weakness, fatigue, chest pain, or shortness of breath. Inadequate oxygenation and ventilation can lead to altered mentation, including anxiety, confusion, obtundation, or coma. Patients with respiratory distress can present with audible wheezing, stridor, or a silent chest. A subjective gauge of respiratory distress is the patient's respiratory effort or "work of breathing."1 Dyspnea, tachypnea, hyperpnea, or hypopnea, ...