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Pulse rate variability in children with disordered breathing during different sleep stages

Heart Rate Variability (HRV), the variation of time intervals between heartbeats, is an indirect and noninvasive method for monitoring the autonomic activities that control heart rate. Traditionally, HRV is measured from the electrocardiogram. In this study, we estimated HRV from the photoplethysmogram (PPG), called pulse rate variability (PRV) and investigated the effects of sleep disordered breathing (SDB) and different sleep stages on it. We recorded the overnight PPG signals from 160 children using the Phone Oximeter, an oximeter connected to a mobile phone, simultaneously with the other signals within standard polysomnography. We analysed the mean pulse-to-pulse intervals, the power of low (LF) and high frequency (HF) bands of PRV and also the ratio of LF power to HF power (LF/HF) in the children with SDB during non-rapid eye movement (non-REM) and rapid eye movement (REM) sleep. The results showed that the normalized LF increased in children with SDB (from 0.26±0.12 to 0.29±0.13 during non-REM sleep and from 0.37±0.12 to 0.40±0.15 during REM sleep), the LF/HF ratio increased in children with SDB (from 0.67±0.55 to 1.05±1.00 in non-REM sleep and from 1.46±2.20 to 1.74±1.38 in REM) and the HF components decreased in children with SDB (from 0.61±0.16 to 0.55±0.17 in non-REM sleep and from 0.47±0.14 to 0.43±0.16 in REM sleep). The results may confirm the pronounced sympathetic and the diminished parasympathetic activity in children with SDB. This study indicates that PRV obtained from the PPG reflects the autonomic regulation of heart rate in disordered breathing during different sleep stages.