This means an overnight sleep study that is done in a sleep laboratory. This is also called Level-1 sleep study. This the gold-standard test to diagnose sleep disorders. A trained technologist is present throughout the time to conduct the test, collect the data and observe the patient. The data is then analysed manually.
We record the following standard parameters during this study, which help to diagnose a variety of sleep disorders. The sleep laboratory may record additional parameters if needed:
- Electroencephalogram (EEG): EEG determines the quantity and quality of sleep. This term means recording the electric activity of brain cells. In order to record EEG, several wires are glued to the scalp. Sleep EEG determines sleep macro-architecture and micro-architecture. The macro-architecture includes the non-REM (non-rapid eye movement) and REM (rapid eye movement) stages of sleep. The sleep microarchitecture includes number of arousals from sleep and EEG cyclic alternating pattern. An arousal (also called micro-arousal) from sleep means lightening of sleep lasting for up to 15 second. It is a measure of sleep disruption. A sleeping person is not aware of these brief interruptions in sleep or the EEG cyclic alternating pattern. The EEG cyclic alternating pattern determines stability of sleep. It also measures sleep disruption. In other words the sleep micro-architecture is an indispensable measure of depth and stability of sleep along with sleep staging.
- Electro-oculogram (EOG): This term means recording the eye movements. This recording is used along with the EEG to determine REM sleep.
- Chin electromyogram (EMG): This term implies recording the electrical activity of chin muscles. This EMG is used to determine REM sleep.
- Limb electromyogram (EMG): This records limb movements during sleep.
- Nasal and oral airflow: This is used to diagnose sleep apnea. It determines the presence or absence of airflow through the nose and mouth and if the person has apneas (pauses in breathing) and hypopneas (shallow breathing).
- Snoring microphone.
- Thoracic and abdominal respiratory effort: This recording is done by placing belts around the chest and belly to record the effort of breathing.
- Pulse oximetry: This means measurement of blood oxygen level with a finger probe.
- Body position: This helps determine if the person is sleeping on his back, sides or the belly.
- ECG or EKG: This term implies recording of electrical activity of the heart.
- Video recording, primarily to record any abnormal behavior during sleep.