What is the role of polysomnography in the diagnosis of central sleep apnea (CSA)?

Updated: Aug 25, 2020
  • Author: Kendra Becker, MD, MPH; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Most diagnoses of central sleep apnea are made on the basis of PSG studies.

In primary central sleep apnea, more than 5 central apneas occur per hour of sleep, each lasting 10 seconds or longer with more than 50% of the events determined to be central rather than obstructive. They appear to be more common during sleep stages 1 and 2. Severe fragmentation caused by apnea may preclude the patient from going into deep sleep (delta sleep). The events are less common during REM sleep for the reasons explained above. The length of the apneic-ventilatory cycle is less than 45 seconds.

The CSB-CSA cycle in heart failure is usually triggered by an arousal resulting in large tidal volume and the consequent lowering of PaCO2. As the patient falls asleep, the apneic threshold is elevated, and ventilation tends to oscillate around the apneic threshold, propagated by slow circulation time. The cycle length of apnea-hyperpnea is usually greater than 45 seconds, is directly proportional to circulation time, and is inversely proportional to cardiac output. Shortening of the cycle length has been reported following cardiac transplantation. The arousals typically occur at the peak of the hyperpneic phase. ICSD-3 [2] criteria require the presence of at least 10 central events per hour of sleep in the crescendo-decrescendo pattern to diagnose CSB.

For the diagnosis of high-altitude periodic breathing, a central apnea-hypopnea index (AHI) of greater than 5 is required at a high altitude. The usual cycle length is from 12-34 seconds. This condition also gives rise to fragmented sleep, increased stage 1 and 2 sleep, and decreased delta sleep. It is only seen during non–rapid eye movement (NREM) sleep and improves over the course of a few days.

Central sleep apnea due to drugs or substance abuse is more common during NREM sleep than REM sleep. [6] Both periodic and nonperiodic breathing patterns can be seen, the cycle length typically being short. An AHI of greater than 5 in the absence of periodic breathing and an AHI of greater than 10 in the presence of periodic breathing is required to make a diagnosis of central sleep apnea due to drugs or substance abuse. Sometimes, ataxic or a Biot breathing pattern is also seen with narcotics use.

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