Breath-to-breath variability correlates with apnea-hypopnea index in obstructive sleep apnea

Background: Breathing in patients with obstructive sleep apnea (OSA) is fre quently interrupted by periods of hypopnea and apnea. There is limited info rmation regarding a possible disturbance of breathing outside these periods . Study objective: To analyze the degree of breathing disturbance during nono cclusion. Design: Prospective determination of breathing variability during full poly somnographic 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 exten t 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 incre ased variability of nonocluded breathing. This effect was present in all sl eep stages, and the extent depended significantly on the degree of disease. Continuous positive airway pressure breathing was able to normalize kurtos is (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 n ormal-length breaths.