Heart rate variability during sleep in infants with bronchopulmonary dysplasia. Effects of mild decrease in oxygen saturation.

We sought to determine whether abnormal heart rate modulation by the autonomic nervous system occurs in patients with severe bronchopulmonary dysplasia (BPD) in relation to sleep stages and mild changes in arterial oxygen saturation SaO2. On 10 oxygen-dependent 7- to 29-month-old infants with BPD, polygraphic recordings, including heart and respiratory rate and body movement detection, were performed. Heart rate variability was evaluated in high (HF), mid, and low (LF) frequency bands. Parameters were analyzed in two ranges of SaO2: normal range, (SaO2 greater than 95%), and mild decrease in (SaO2, values of 90 to 94%). In contrast to what is normally observed, LF at normal SaO2 was less marked in rapid eye movement, (REM) sleep than in non-rapid eye movement (NREM) sleep stage 2. A mild decrease in SaO2, as compared with a normal SaO2 value, was associated with: (1) a heart and respiratory rate acceleration, (2) a decrease in HF in REM sleep (p < 0.02); (3) an increase in LF in NREM sleep stage 2 (p < 0.02), intensifying the change observed in a normal SaO2 level. These data show that a mild decrease in SaO2 increases modifications of autonomic control observed in infants with severe BPD.