Background: Breathing in patients with obstructive
sleep apnea (OSA) is frequently interrupted by periods of hypopnea and
apnea. There is limited information regarding a possible disturbance of
breathing outside these periods.
Study objective: To
analyze the degree of breathing disturbance during nonocclusion.
Design: Prospective determination of breathing variability
during full polysomnographic sleep studies.
Breath-to-breath variation was monitored in 34 patients with OSA and in
9 healthy subjects.
Measurements and results: All
breath-to-breath intervals were automatically analyzed from flow
signal, displayed, and manually corrected for artifacts. Distribution
of all nonapneic breath intervals was analyzed for the extent of
difference from a normal distribution pattern by specifying kurtosis.
In untreated OSA patients, kurtosis was significantly reduced
(0.0 ± 0.5, mean ± SD) compared to control subjects
(0.8 ± 0.5), indicating increased variability of nonoccluded
breathing. This effect was present in all sleep stages, and the extent
depended significantly on the degree of disease. Continuous positive
airway pressure breathing was able to normalize kurtosis (1.0 ± 0.9)
Conclusions: Breathing in OSA is not only
characterized by interruptions of breathing during occlusion, but by a
greater variation in the pattern of normal-length