Severe hypoxemia in children with upper airway obstruction during sleep does not lead to significant changes in heart rate

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Abstract
Life-threatening cardiac arrhythmias, including bradyrhythmias, are well-known sequelae of obstructive sleep apnea syndrome (OSAS) in adults and are associated with apnea and severe hypoxemia. Since the clinical expression of OSAS in children is different, we questioned whether arrhythmias are a common feature of pediatric OSAS. Therefore, we analyzed R-R interval patterns from 12 subjects (age 8 months to 14 years) with OSAS in detail. The diagnosis of pediatric OSAS is based on clinical signs of loud snoring and paradoxical respiratory efforts, as well as elevated end-tidal carbon dioxide tension (PETCO2) and major phasic decreases of oxyhemoglobin saturation (SaO2). Two hundred and nine episodes of severe hypoxemia, defined as SaO2 values ⩽85% lasting ⩾30 seconds, were identified. Only 29 (14%) of these episodes were associated with obstructive apneas. The R-R intervals were analyzed before and during each desaturation. Compared to baseline, mean and minimum R-R intervals (RR,mean, RRmin) decreased during the desaturation episodes (P < 0.05), while maximum R-R interval (RRmax) increased (P < 0.05). Although the absolute changes in all parameters were significantly different from baseline, the magnitude of these changes was small, with a mean of −5.3%, −12.2%, and 10.4% for RRmean, RRmin, and RRmax, respectively. No child had life-threatening arrhythmias. Although severe hypoxemia existed in these children, the magnitude of the R-R interval changes was modest, and profound bradycardia as described in adults, was rare. We conclude that in children with suspected OSAS, changes in R-R interval and presence of life-threatening arrhythmias cannot be used as a screening tool to assess the severity of disease or blood gas abnormalities. We speculate that the difference in heart rate patterns between children and adults may depend, in part, on the degree of airway closure and associated changes in pleural pressure. Pediatr Pulmonol. 1993; 16:362–369.