The gold standard for determining if someone has obstructive sleep apnea (OSA) is an overnight sleep study (polysomnography). This test is ordered by a physician, and can be performed at a sleep center (monitored) or at home (unmonitored). Often times, insurance companies determine which type of test will be conducted. Sleep studies have two components. The diagnostic segment determines whether sleep apnea is present, while the treatment segment is used to determine the CPAP setting for a particular individual.
Monitored sleep studies have several advantages. Sleep clinics collect more detailed information than can be obtained during a home study. Someone is also available to assist with equipment hook up and can troubleshoot problems should they arise. Monitored sleep studies may be performed as separate diagnostic and treatment tests or as a “split night” study that combines both tests in a single night. The draw backs of these studies include greater cost and the possibility of needing to wait longer for the study to be performed. If you are scheduled for one of these tests, consider bringing with you important “creature” comforts such as your pillow. This will help make your experience more pleasant.
Home studies offer you the opportunity to have the sleep study performed in the comfort of your own home. The information collected during this test is not as detailed as that of a monitored study. If there are equipment problems, or if the monitors come off during sleep, the study will need to be repeated. Diagnostic and treatment studies are always performed separately.
You should consider starting a personal file at home for your test results. If you move, or change providers, this information will help ensure that you receive appropriate care. While there is a great deal of information collected during the sleep study, there are two critical pieces of information to understand. The first is the apnea/hypopnia index (AHI), which can also be referred to as the respiratory distress index (RDI). This represents the number of times someone stops breathing or has reduced airflow per hour. Most sleep labs consider 0-5 events/hour to be normal, 6-15 events/hour to be mild OSA, 16-30 events/hour to be moderate OSA, and greater than 30 events/hour to be severe sleep apnea.
The other test result to be aware of is lowest blood oxygenation level. Ideally, blood oxygenation levels should remain above 90%. Some sleep centers advise people with oxygen desaturations of 85% and below to obtain expedited treatment.