What is the role of polysomnography in the workup of hypoventilation syndromes?

Updated: Jul 22, 2021
  • Author: Jazeela Fayyaz, DO; Chief Editor: Guy W Soo Hoo, MD, MPH  more...
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Polysomnography should be performed in all patients with OHS because the majority of these individuals also have OSA. Polysomnography involves monitoring of multiple physiologic variables to include respiratory effort, airflow, oxygen saturation, sleep stages, body position, limb movements, and electrocardiogram. [14]

Sleep stages and arousals are monitored by electroencephalogram, to determine brain wave activity; electro-oculogram, to determine eye movement; and submental electromyogram, to detect muscle tone. The electro-oculogram and electromyogram facilitate the determination of the REM sleep stage, which is associated with decreased muscle tone and increased frequency of obstructive apneas.

Respiratory effort is recorded using devices to measure abdominal and chest wall movement. These devices include strain gauges, impedance devices, electromyographic bands, and an esophageal balloon with respiratory inductive plethysmography.

From the collected data, sleep stage distribution, arousals, apneas, and hypopneas can be quantitated and central and obstructive apneas can be differentiated. The apnea index and apnea-plus-hypopnea index (AHI) can be calculated by dividing the total number of apneas or apneas plus hypopneas by the total sleep time. The AHI also is known as the respiratory disturbance index. An AHI is considered abnormal at 5 per hour, and an AHI of 5-15 represents mild OSA.

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