Polysomnography is a series of tests which are conducted on someone who is asleep. Also known as a sleep study, polysomnography is used to diagnose sleep disorders so that a doctor can make treatment recommendations for the patient. This testing is usually performed in a sleep lab, a facility dedicated to the purpose of conducting sleep studies, under the supervision of a doctor or a polysomnography technician who specializes in managing sleep studies.
The term “polysomnography” comes from the Greek words for “many,” “sleep,” and “writing.” As the etymology of the term suggests, polysomnography results in a polysomnographic printout which collects the readings from various pieces of medical equipment. The information can also be in digital form, depending on how the sleep lab likes to handle its data. By studying the information collected, a doctor can learn more about a patient's condition.
A number of different things are measured during polysomnography, including brain activity, blood pressure, dissolved oxygen in the blood, respiration rate, airflow, eye movements, cardiac activity, and muscle movements. These measurements are taken with the use of telemetry equipment which connects to leads attached to the patient's body. The equipment is usually located in another room for the purpose of remote monitoring, and so that the patient does not feel intimidated by being surrounded by medical equipment.
Patients usually arrive for a polysomnography in the evening. They are advised to keep their routines normal, eating and exercising then they normally do, and they are told not to take sleep medications. Once they arrive, patients are hooked up to the equipment and shown how it works, and then allowed to go to bed. Ideally, the patient will fall asleep, allowing data to be collected, although some patients have trouble getting to sleep in an unfamiliar environment, especially if they are already struggling with a sleep disorder.
In the morning, the doctor can read the results and discuss them with the patient. Polysomnography can also take place during the day for patients who are on unusual sleep schedules, or who have trouble sleeping at night. The study can also include tests to determine day time sleepiness levels.
Patients can also participate in what is known as a “split study.” In a split study, the patient is allowed to sleep under observation for the first part of the night, and for the second part of the night, a treatment for a sleep disorder such as a continuous positive airway pressure (CPAP) machine is used. The advantage to a split study is that it allows an intervention to be tested right away if the patient has an obvious problem, and it allows the patient to spend a single night in the sleep clinic, rather than two.