Diagnosing Sleep Apnea
A variety of tests can be used when diagnosing sleep apnea. These include pulmonary function tests, polysomnography, and the multiple sleep latency test. Physicians continue to try to develop other simple and economic procedures for the early diagnonsis of sleep apnea.
Pulmonary Function Tests
A Pulmonary function test taken by sleep apnea patients may show normal results unless the patient has a coexisting lung disease. To make a definitive diagnosis of sleep apnea, the physician may order an all-night sleep apnea test to evaluate the patient's sleep stages, and of the status of breathing and gas exchange during sleep.
Polysomnography is a group of tests that monitors a variety of functions during sleep. These include:
- sleep state
- electrical activity of the brain (EEG)
- eye movement (EOG)
- muscle activity (EMG)
- heart rate
- respiratory effort
- low oxygen and carbon dioxide levels
Other tests may be ordered depending on a particular patient's needs.
Polysomnography sometimes helps to distinguish between different sleep disorders. These tests are used both as a sleep apnea screening and to diagnose the disorder and determine its severity.
Multiple Sleep Latency Test
The Multiple Sleep Latency Test is done during normal working hours. It consists of observatios, repeated every 2 hours, of the time taken to reach various stages of sleep.
In this test, people without sleep apnea take more than 10 minutes to fall asleep. On the other hand, patients with sleep apnea or narcolepsy fall asleep fairly rapidly. When it takes the patient an average of less than 5 minutes to fall asleep, it is considered pathological sleepiness. There is thus some uncertainty in the diagnosis if the sleep latency period (speed of falling asleep) is between 5 and 10 minutes.
This test is important because it measures the degree of excessive daytime sleepiness and also helps to rule out narcolepsy, which is associated with the onset of REM sleep (dream sleep) in many of the naps.
Sleep Apnea Doctors
The general physician may sometimes recognize sleep apnea, but specialists in neurology, psychiatry, pulmonary medicine and cardiology may be needed for accurate diagnosis and management.
Diagnosis of sleep apnea is difficult because disturbed sleep can cause various other diseases or make them worse.
Several major medical centers now have pulmonologists, neurologists, and psychiatrists with specialty training in sleep disorders on their staff. Although an evaluatation for sleep apnea can sometimes be done at home, it is more reliable if it is done in a sleep laboratory.
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Swanson, Jennifer. Sleep Disorders Sourcebook. Detroit, Michigan: Omnigraphics, Inc., 1999: 178-179.