Effects of pathological respiratory pattern on heart rate turbulence in sleep apnea

Although baroreflex sensitivity (BRS) impairments are involved in cardiovascular disease's development in OSAS, the mechanism underlying this derangement is rather unknown. BRS can be non-invasively assessed by heart rate turbulence (HRT) analysis. This is the first study separately assessing HRT during normal (NR) and obstructive apnoea pattern (OS) with the aim to describe the effects of pathological respiratory pattern on HRT in OSAS. HRT is characterized by an early rate acceleration (TO) and a late deceleration (TS) indexes describing heart rate fluctuations following spontaneous isolated ventricular premature complexes. Results on 20 polysomnography of severe OSAS pts. (age 62±14) showed that, while the TO during OA is not significantly different from those of NR epochs (-0.3±1.8 vs. -0.4±1.2), the TS during OA is very significantly higher than in NR phases (7.4±5.4 vs. 2.7±1.2 , p<0.001 Wilcoxon matched pairs test). This novel finding showed a not previously known paradoxical TS increasing during OA episodes followed by a marked decrease during subsequent NR phases. This can be related to repetitive brief inspiration against an obstructed airway, generating intrathoracic pressure changes, that in the initial phase results in marked hypotension and a paradoxical reduction sympathetic activity while, toward the end generates a gradually increasing sympathetic activity. Such deeper understanding of the integrated autonomic response in different OSA pathophysiological conditions could be useful to address an overall cardiorespiratory assessment and treatment in sleep-related breathing disorders.