Split Night

In order to save time (and often money), a split-night study is sometimes ordered. The first half of the test is the same as a normal polysomnogram (see above). If significant obstructive breathing (apnea) is noted during this time, a mask is applied to the nose and the test continues as a CPAP study (see above). Under ideal conditions, this takes the place of two separate tests. In reality, however, this test is often inconclusive. Regulations require that you sleep for at least two hours before the CPAP is applied, and demonstrate a large number of obstructed breathing events before beginning treatment.

Because of the strange environment and the anxiety sometimes associated with testing, it may take longer than usual to fall asleep, or you may awaken for some time. As a result, it may take a number of hours before two hours of sleep have occurred. This leaves less time to perform the CPAP procedure. After being awakened to begin the CPAP procedure, it may take some time to adjust and return to sleep, further limiting the ability to find an adequate pressure. In addition, the breathing events may only occur later in the night, during specific stages of sleep, or only in certain body positions, usually while flat on your back.

It may take the entire study before sufficient data has been documented to qualify for treatment. Because of this, many “split-night” patients have to return to the sleep center for a second night of (CPAP) therapy anyway.