Autonomic imbalance during apneic episodes in pediatric obstructive sleep apnea

Objectives: To investigate the activity of the autonomic nervous system (ANS) during sleep in children with obstructive sleep apnea (OSA), in order to detect a possible cardiac ANS imbalance analyzing heart rate variability (HRV).

Methods: 43 subjects between 4 and 12 years of age (7.26 ± 2.8 years), undergoing a diagnostic assessment for OSA were evaluated. A time domain index (R-apnea index) was developed to evaluate HRV strictly related to obstructive events during sleep. Poincaré plot of RR intervals during the whole night was calculated.

Results: R-apnea index was negatively correlated with apnea hypopnea index (AHI) (r=-0.360, p=0.028). AHI and the duration of the disease were the only variables that were significantly correlated with R-apnea index. Three groups were subsequently created according to polysomnographic findings considering AHI. R-apnea index resulted significantly lower in patient with severe OSA compared to primary snoring/mild OSA subjects (p<0.05). Looking at Poincaré plot, SD1 showed a diminishing trend with severity of OSA, however not reaching statistical significance.

Conclusions: Our findings suggest an autonomic impairment in OSA children evidenced by the altered HRV both in the very short term (R-apnea index) and in short term (SD1).

Significance: R-apnea index is an easy and cheap method to undelay early ANS imbalance.