A sleep study or polysomnogram (PSG) is a test that electronically measures and records specific physical activities during sleep. The test result data is analyzed by a sleep disorder doctor in order to determine whether or not a person has a sleep disorder and, if so, the specific type.
The test is performed in a Sleep Testing Center and involves spending the night in order to be monitored by a qualified sleep technician. Testing centers provide private comfortable, hotel like rooms and beds. Adjacent to the bedroom is a central monitoring room, where the technicians monitor sleeping patients.
During the test you are hooked up to equipment that monitors heart, lung and brain activity, breathing patterns, leg movements and blood oxygen levels, while you are asleep. During the sleep study, surface electrodes are placed on the patient’s face and scalp, to measure brain and muscle activity. Belts are placed around the chest and the abdomen to measure breathing effort. An oximeter probe is placed on the finger to measure the blood oxygen content. While the equipment may look uncomfortable, most patients fall asleep with little difficulty. The results of the test will determine appropriate treatment options.
Most centers conduct a 2 part test or ‘split-night’ study. During this test, you are monitored for several hours to achieve a baseline of sleep activity. If the baseline indicates sleep apnea, then the patient is awakened and provided a CPAP machine. The patient then goes back to sleep, and the technician then remotely titrates the CPAP pressure to determine the necessary pressure to eliminate apneas and snoring.
On the first night, the patient is monitored to achieve baseline sleep patterns. Then the patient returns for a second night, to be titrated with CPAP. Some centers practice two-night studies, although most achieve desired results with a split-night study.
A two-night study may also be necessary, if for some reason, the patient does not achieve an adequate baseline during a spit-night study. This can be due to inadequate sleep time or a variety of other reasons.
Some insurance carriers require that a home sleep study be conducted instead of an in lab test. This test should correctly be termed home cardiorespiratory monitoring because the test does not determine if the patient is actually sleeping. As a rule, these tests should be performed on patients in whom there is a high index of suspicion of sleep apnea. These tests are less expensive to conduct, but are also limited in the amount and type of date collected. While HST studies can demonstrate apnea events and may indicate a proper diagnosis, they may fail to record adequate diagnostic information.
If your insurance requires you to have an HST, pay special attention to the proper use of the equipment. If following the test and diagnosis, you still experience symptoms, contact your physician and request an in lab study.
If you are diagnosed with sleep apnea and prescribed CPAP therapy, it is essential to use the equipment all night, every night. It will take some time to become accustomed to sleeping with CPAP, and may require trial of several mask, before you are comfortable.
Proper mask fitting and proper instruction on the use of your CPAP machine, is critical to successful use.