The PolySomnoGram(PSG) is our most common test. It monitors sleep, breathing, movements and behaviors overnight (usually). 6-8 Electrodes glued to the scalp identify sleep vs awake. Electrodes around the eyes and under the chin detect REM sleep (dreaming). A thermistor positioned at the nose and mouth detects airflow. Elastic bands on the chest and belly assess effort. If you have effort but no airflow, you have obstructive sleep apnea (OSA). We check the effects of apnea with ekg, finger oximetry and snoring microphone. Leg movement electrodes detect restless legs. A video camera identifies position and documents sleep walking and other behaviors. A PSG may be done with cpap to titrate optimal pressure and equipment in various sleep stages and positions.
Home Respiratory Testing (HRT) is a simpler but more limited test that detects apnea with a nasal thermistor and effort bands while monitoring position and oximetry. It does not detect sleep and results are misleading because awake events cannot be excluded. HRT is useful for patients with strong signs of OSA but it fails to address questions about fatigue, insomnia, restless legs, sleep quality and other causes of poor sleep. We will use HRT to cut costs of testing but recognize that we are sacrificing quality and information.
Overnight Oximetry is a diode taped on the finger with a wired recorder of blood oxygen levels and pulse rates. Oxygen saturations should be over 89% during sleep and over 92% awake. This is a simple screening tool to detect hypoxia from OSA but it has false positives and negatives. If you stay awake all night, oximetry will look normal. If you get up and wiggle the wire, it may look like sleep apnea.
A PAP Nap is a daytime session with limited monitoring to improve a patient's use of cpap. The technician assists with mask selection, fitting and adjustments. The cpap pressure can be adjusted for optimal comfort and effectiveness.
The Multiple Sleep Latency Test (MSLT) is a series of 4-5 twenty minute naps spaced every 2 hours to assess sleepiness during the day. This is an objective documentation of fatigue and sleepiness. It is useful in assessing Narcolepsy and driving/work safety. The average time to fall asleep is 13-15 minutes for normal people but those with OSA and Nacrolepsy fall asleep in 2-5 minutes. Abnormal REM timing is the hallmark of Narcolepsy and the MSLT reveals dreaming during naps in Narcoleptics which normal individuals rarely have. This test is usually done after a PSG documents sleep duration and quality the previous night.