Pediatricians are concerned about appropriate monitoring of vital functions in infants both in the hospital and at home. Besides respiratory frequency and apnea duration, most electronic monitors evaluate instantaneous heart rate and activate an auditory and visual alarm at a preset value. The choice of the low heart-rate threshold might be based on either statistical probability or on clinical significance.
In this issue of AJDC, Hodgman et al1 report observations of heart rates in 14 full-term and 19 preterm infants at several chronological ages. Having selected an operational definition of transient episode of bradycardia, they analyzed tracings collected over one night in the laboratory. The definition included episodes of fall in heart rate to an instantaneous value equal to or less than 90 beats per minute, or a fall of 30 beats per minute when associated with apnea or a decrease in transcutaneous Po2 of 15 mm Hg