Heart rate variability in children with sleep disordered breathing

Background: Autonomic nervous system activity during sleep can be characterized by dynamic changes in heart rate, catecholamine release, peripheral arterial tone, and systemic blood pressure. There is a particular growing interest in understanding heart rate variability (HRV) as marker of sympathetic and parasympathetic drive. The presence of autonomic dysregulation can be observed in sleep disorders such as obstructive sleep apnea and be associated with cardiovascular diseases. Aim of review: a. Highlight the consensus definition for heart rate variability (HRV) and key measurements based on spectral analysis b. Review the anatomy and physiology of the autonomic nervous system c. Explain the normal autonomic modulations occurring across sleep stages of children and the variance by age d. Review the HRV parameters in relation to sleep disordered breathing in children e. Examine the association with autonomic dysregulation and myocardial dysfunction in sleep disordered breathing. f. Study the effect on HRV after therapeutic interventions for sleep disordered breathing. Key Scientific Concepts of Review: a. Measurements of Heart rate variability (HRV) can be based on Time-Domain or Frequency Domain methods. b. Slow wave sleep is thought to be vagally dominated, while REM sleep has a higher sympathetictone. c. Age is the strongest determinant of HRV parameters. d. Children with Sleep Disordered Breathing may present with varying degrees of autonomic dysfunction, including increased sympathetic tone, increased sympathetic responsiveness, impaired down-regulation of sympathetic activity, and an imbalance at times for greater sympathetic dominance relative to parasympathetic activity.