Polysomnography, also called a sleep study, is a test used to diagnose sleep disorders. Polysomnography records your brain waves, the oxygen level in your blood, heart rate and breathing, as well as eye and leg movements during the study. Polysomnography usually is done at a sleep disorders unit within a hospital or at a sleep center. You'll be asked to come to the sleep center in the evening for polysomnography so that the test can record your nighttime sleep patterns. Polysomnography is occasionally done during the day to accommodate shift workers who habitually sleep during the day. In addition to helping diagnose sleep disorders, polysomnography may be used to help adjust your treatment plan if you've already been diagnosed with a sleep disorder. Polysomnography monitors your sleep stages and cycles to identify if or when your sleep patterns are disrupted and why. The normal process of falling asleep begins with a sleep stage called non-rapid eye movement (NREM) sleep. During this stage, your brain waves, as recorded by electroencephalography (EEG), slow down considerably. Your eyes don't move back and forth rapidly during NREM, in contrast to later stages of sleep. After an hour or two of NREM sleep, your brain activity picks up again, and rapid eye movement (REM) sleep begins. Most dreaming occurs during REM sleep. You normally go through four to six sleep cycles a night, cycling between NREM and REM sleep in about 90 minutes. Your REM stage usually lengthens with each cycle as the night progresses. Sleep disorders can disturb this sleep process. Polysomnography monitors your sleep stages and cycles to identify if or when your sleep patterns are disrupted.
A split-night study is an overnight polysomnogram performed with a two-hour period of baseline sleep study recording, followed by a CPAP titration study if it is determined to be indicated by the presence of clinically significant sleep apnea. CPAP (Continuous Positive Airway Pressure) is a device utilized to treat obstructive sleep apnea. It consists of nasal mask, connected by tubing to an air compressor. The mask fits snugly over or under the nose, and the air compressor increases the pressure of the air you breathe in. In a CPAP titration study the pressure is gradually increased until a pressure is reached that results in the resolution of the sleep apnea. CPAP is the most effective treatment available for obstructive sleep apnea.
In some cases, your doctor may provide you with simplified tests to be used at home to diagnose sleep apnea. These tests usually involve measuring your heart rate, blood oxygen level, airflow and breathing patterns. If you have sleep apnea, the test results will show drops in your oxygen level during apneas and subsequent rises with awakenings.
Typically hook-up of sensors in HST will require: Wrapping a RIP belt around the chest, placing and securing a pulse ox on the patient’s index finger, and wearing a nasal cannula. This is only minimally invasive and painless. Sometimes a thermistor may be used along with the nasal cannula to confirm apneas.
The multiple sleep latency test (MSLT) tests for excessive daytime sleepiness by measuring how quickly you fall asleep in a quiet environment during the day.
The MSLT is a full-day test that consists of five scheduled naps separated by two-hour breaks. During each nap trial, you will lie quietly in bed and try to go to sleep. Once the lights go off, the test will measure how long it takes for you to fall asleep. You will be awakened after sleeping 15 minutes. If you do not fall asleep within 20 minutes, the nap trial will end.
Each nap will be taken in a dark and quiet sleep environment that is intended for your comfort and to isolate any external factors that may affect your ability to fall asleep. A series of sensors will measure whether you are asleep. The sensors also determine your sleep stage.