Heart rate variability during sleep in infants with bronchopulmonary dysplasia: effects of mild decrease in oxygen saturation

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From: Chest(Vol. 106, Issue 6)
Publisher: Elsevier B.V.
Document Type: Article
Length: 3,599 words

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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 Sa[O.sub.2]. 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 Sa[O.sub.2]: normal range, (Sa[O.sub.2] greater than 95%), and mild decrease in (Sa[O.sub.2], values of 90 to 94%). In contrast to what is normally observed, LF at normal Sa[O.sub.2] was less marked in rapid eye movement, (REM) sleep than in non-rapid eye movement (NREM) sleep stage 2. A mild decrease in Sa[O.sub.2], as compared with a normal Sa[O.sub.2] 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 Sa[O.sub.2] level. These data show that a mild decrease in Sa[O.sub.2] increases modifications of autonomic control observed in infants with severe BPD.

(Chest 1994; 106:1711-16)

BPD=bronchopulmonary dysplasia;

HF=high frequency;

HR=heart rate;

HRV=heart rate variability;

LF=low frequency;

MF=mild frequency;

NREM=non-rapid eye movement;

REM=rapid eye movement;

Sa[O.sub.2]=arterial oxygen saturation

Key words: bronchopulmonary dysplasia; heart rate; hypoxia; infants; movements; respiration; sleep

Sleep-related hypoxemia is a potential complication of bronchopulmonary dysplasia (BPD). Unexpected and frequent episodes of arterial oxygen desaturation have been described in these infants during sleep, even when they had acceptable oxygenation while awake.(1)(2) Sleep hypoxemia during BPD may produce respiratory(3) and cardiac adverse effects.(4) Acute hypoxic challenge has been shown to provoke prolonged apnea and severe bradycardia in infants with BPD.(5) This suggests that abnormal heart rate modulation by the autonomic nervous system may occur in BPD patients and may be related to hypoxia.

Analysis of heart rate variability (HRV) gives reliable information about both sympathetic and parasympathetic autonomic control of the heart rate (HR).(6) Three types of HRVs have been identified: (a) high-frequency (HF) HRV, related to respiratory cycle (respiratory sinus arrhythmia), known to be under parasympathetic control; (b) mid-frequency (MF) HRV variations, known to reflect baroreceptor activity, and (c) low-frequency (LF) HRV, of less clear origin, considered to be under both parasympathetic and sympathetic control. Changes in HRV with sleep stage have been reported as follows: (a) high amplitude of HF HRV related to prevailing parasympathetic activity in non-rapid eye movement (NREM) sleep and (b) high amplitude of LF HRV related to prevailing sympathetic activity in rapid eye movement (REM) sleep.(7)(8)(9) To the best of our knowledge, no studies have been reported on HRV during different sleep stages in BPD patients with regard to different ranges of arterial oxygen saturation (Sa[O.sub.2]) levels. We therefore conducted a study to analyze changes in HRV during sleep, comparing normal Sa[O.sub.2] and mild decreases in Sa[O.sub.2] values in BPD patients.

SUBJECTS AND METHODS

Subjects

A group of 10 patients were...

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Gale Document Number: GALE|A16280657