Sleep Apnea Test

Sleep apnea (apnea: Greek for “without breath”) is a sleeping disorder where a subject frequently stops breathing during sleep.  Because the subject is unaware of these breathless episodes, and because waking symptoms are vague: daytime grogginess, headache, and dry throat, the subject rarely feels the need to check with a physician.  Family and friends are who usually report the problem.  Sleep apnea’s outward symptom is loud and excessive snoring.  Though the symptoms are indistinct, the consequences of undiagnosed sleep apnea can be life-threatening hypertension and cardiovascular disease.  To definitively diagnose the disorder requires a sleep apnea test.

The optimal sleep apnea test is polysomnography, (PSG) performed in a sleep lab.  PSG consists of observing the patient overnight during sleep, monitoring sleep state, heart rate, breathing, blood oxygen levels, eye movement and muscle activity.  In normal adults during REM (rapid eye movement) sleep, the muscles of the throat and neck are relax, allowing the tongue and soft palate to relax as well.  In sleep apnea, these tissues relax so much that they can reduce and/or block the airway (often the source of snoring).  Blood oxygen levels drop, the brain arouses the body enough to breathe, waking the patient momentarily, but rarely to full wakefulness.  These breathless episodes are called apnea events.  The results of this sleep apnea test: the number of apnea events, how long each event lasts, blood oxygen level, percentage of sleep spent in REM, snoring, etc., allows the physician to diagnose the disorder and its severity.

Conducting a sleep apnea test via PSG in the sleep lab is an important diagnostic tool, but has drawbacks.  First, the patient is asked to sleep in an unfamiliar environment.  Secondly, the patient is connected to multiple wires and to multiple monitors.  Lastly, the patient is being watched by other people.  Thus, the patient often doesn’t sleep well.

To help alleviate the awkwardness of sleeping in a lab, a similar type of sleep apnea test can be performed at home.  Also a type of PSG, a monitor records heart rate, how air moves in and out of the lungs, the blood oxygen level, and the effort required to breathe.  For this sleep apnea test, a technician goes to the home and hooks the patient to the electrodes.  The patient goes to sleep as usual, and the technician returns the next morning to retrieve the monitor and send the results of the sleep apnea test to the patient’s physician. 

Another home sleep apnea test system, recently approved by the Federal Drug Administration (FDA), the Watch_PAT100 by Itamar Technologies which consists of a fingertip probe and a wearable wrist unit.  Both devices are placed on the wrist and finger just before going to bed.  During sleep, the system measures blood oxygen saturation levels, changes in blood flow and pulse rate.  The signals are recorded onto a memory card.  The memory card can be removed by the physician and downloaded into a computer for analysis.  Comparable to polysomnography, this device is still being evaluated.

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