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Breath-to-breath variability correlates with apnea-hypopnea index in obstructive sleep apnea
P Kowallik1, I Jacobi, A Jirmann
1Department of Medicine, University of Würzburg, Germany. kowallik@mail.uni-wuerzburg.de
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.
Patients:
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) immediately.
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 breaths.