The polysomnography test is performed by sleep disorder labs. The test is prescribed in cases where patients report excessive daytime sleepiness, insomnia and snoring. Because some sleep disorders cause or complicate conditions such as hypertension, doctors may recommend a polysomnography test for their patients who have the risk factors for sleep apnea, such as being overweight, have a large neck, or a narrow sinus passage or esophagus.
Identification
Patients coming to the sleep lab for a polysomnogram will be spending an entire night in the lab. After arriving they complete questionnaires that describe their sleep habits and list any medications they have taken that day. Then patient is then given time to change into their sleeping clothes and perform any bedtime routines such as brushing their teeth. The sleep technician then will apply electrodes and other monitors to the patient. Once the wires are all plugged into the computer monitoring the readings and the technician has verified that the readings are clear the patient is then allowed to sleep. In the morning the monitors are removed, the patient fills out a final questionnaire about their sleep quality that night and then they are discharged. The results of the polysomnography test is then sent to the patient's doctor for interpretation.
Function
The majority of the electrodes the patient wears during the study are to record EEG, which are brainwaves. As the patient sleeps their brain waves change. Wake brain waves are fast alpha waves. As the person falls asleep the brain waves slow down. There are three stages of non-REM sleep. Stage 1 is the lightest stage and is experienced as light dozing. Stage 2 is a transitional stage where the body rests quietly. Stage 2 by itself is not very refreshing sleep. Stage 3 is has the slowest brainwaves. During this stage of sleep growth hormone is released which helps children to grow and helps adults to repair and refresh their bodies. The final stage of sleep is REM, which stands for rapid eye movement. REM brainwaves are similar to the waves seen in stage 1 sleep. The difference is the eye movements and the lack of muscle tension. REM is the stage when people dream. People who do not get enough REM sleep suffer from depression and are irritable. Chronic REM deprivation can lead to psychological and emotional disorders. Knowing the stages of sleep a patient has, and how long they spend in each stage is important in determining the type of sleeping disorder a patient has and how severe the disorder is.
Features
Polysomnography tests also monitor breathing patterns. Patients wear belts around their stomach and chest to monitor how much effort they make to breath. A small temperature probe called a thermister is placed beneath the nose and in front of the mouth. As a person inhales it cools the probe and as they exhale it warms it. This is how the tests shows how much the patient is actually breathing. A probe on the finger called a pulse oximeter monitors the blood oxygen level. These probes are used to determine if the patient has apnea, which kind and how severe.
Considerations
There are three different kinds of . Obstructive apnea occurs when there is a complete blockage in the airway. This shows up on the polysomnograhy test as a flat line on the thermister while effort is still seen in the belts around the chest and stomach. A hypopnea is when the airflow is reduced but not completely stopped, indicating an incomplete but significant block in the airway. A central apnea occurs when the patient's body no longer attempts to breath. This appears on a polysomnogram as flat lines in both the airflow and the respiratory effort channels. The severity of each type of apnea is determined by how low the blood oxygen level reaches as a result of the apnea. Most people who snore have at least one type of sleep apnea.
Effects
For the polysomnogram electrodes are also placed on the muscles of the calves. These leg leads monitor leg movements during sleep. A common sleep disorder is periodic limb movement syndrome. This is when the legs twitch or kick during sleep. This can cause the patient to keep waking throughout the night, disrupting the quality of . It can also disrupt the sleep of the patient's spouse or bed partner.
Significance
REM behavior disorders and other sleep disruptions such as sleep walking and night terrors can also be detected during the polysomnography test. These are detected on the test by large movements in the EMG (muscle movement) channels. The sleep technician monitors patients all night and make notes regarding the specific behaviors patients display during their sleep test.
Prevention/Solution
Following the sleep test the record is scored, which is when sleep stages are assigned to every 30-second page of the recording. All apnea and sleep movements are marked in the record, along with any resulting sleep disruption such as waking up of dropping into a less restful stage of sleep. The record is used to produce a report that the doctor uses to determine a diagnosis and treatment plan. Most movement disorders are treated with medication. Patients who have sleep apnea are sometimes treated with surgery, but most return to the sleep lab for a CPAP study. CPAP is a machine with a hose attached to a mask that the patients wear at night. The machine used air pressure to open the collapsing air passages while the patient sleeps, allowing them to sleep uninterrupted by apnea.
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