A polysomnogram (PSG) is a procedure that utilizes electroencephalogram, electro-oculogram, electromyogram, electrocardiogram, and pulse oximetry, as well as airflow and respiratory effort, to evaluate for underlying causes of sleep disturbances. PSG is considered to be the gold standard for diagnosing sleep-related breathing disorders, which include obstructive sleep apnea (OSA), central sleep apnea, and sleep-related hypoventilation/hypoxia. (Rundo, 2019)
PSG is non-invasive and consists of a simultaneous recording of multiple physiologic parameters related to sleep and wakefulness. PSG or sleep study can directly monitor and quantify the number of respiratory events (ie, obstructive, central, or complex) and the resultant hypoxemia and arousals related to the respiratory events or even independent of the respiratory events. (https://emedicine.medscape.com/article/1188764-overview)
The results of PSG should be interpreted in the context of a patient's history and medications and observation in the sleep laboratory.
TYPES
ANOTHER WAY TO CLASSIFY IS BY THE NUMBER OF CHANNELS:
I and II are the most common studies.
Examples of channels are: EEG, Air flow, muscle tone, leg movements, eye movements, ECG, ox saturation, respiratory movements, snoring. Most of the home studies do not measure brain waves.
PARAMETERS
1. AHI: Apnea/Hypopnea Index (AHI): The scale of AHI is:
2. Sleep Position: AHI when the patient is sleeping supine versus on their side.
3. O2 Saturation: What is the O2 saturation nadir (lowest point), and how much time did the patient spend with an O2 saturation below 90%.
4. RDI (respiratory distress index) = AHI + RERAS (effort arousal).
4. Sleep Stages:
REM: 25% of night
NREM:
To identify risk of OSA use STOP Bang.
To identify sleepiness use Epworth.
Rundo JV, Downey R 3rd. Polysomnography. Handb Clin Neurol. 2019;160:381-392. doi: 10.1016/B978-0-444-64032-1.00025-4. PMID: 31277862.
Jafari B, Mohsenin V. Polysomnography. Clin Chest Med. 2010 Jun;31(2):287-97. doi: 10.1016/j.ccm.2010.02.005. PMID: 20488287.