Abstract

A system for simultaneous 24-hour tape recording of ECG and respiration has been developed and used in the study of 4 groups of newborn infants. In 50 randomly selected, healthy term infants, the mean lowest heart rate (>9 beats' duration; was 88 ± 13. 14 (28%) infants had junctional escape rhythms, 5 had supraventricular, and 2 ventricular premature beats. 34 (68%) subjects had apnoeic episodes ≥10 seconds' duration; the 95th centile for maximum duration of apnoea was 18 seconds, the longest episode being 28 seconds. Episodes of bradycardia <100/minute were associated with 50 of a total of 288 episodes of apnoea of 10-14 seconds, with all 4 episodes of 15-19 seconds, and with both episodes ≥20 seconds.

In 100 randomly selected, healthy, preterm or low birthweight infants studied within 5 days of their discharge from hospital, the mean lowest heart rate was 91 ± 18. 18 had junctional, one idioventricular, and 3 both junctional and idioventricular escape rhythms. Two had supraventricular and 6 had ventricular premature beats. 66 subjects had apnoeic episodes ≥10 seconds' duration; the 95th centile for maximum duration of apnoea was 20 seconds, the longest episode being 52 seconds. Episodes of bradycardia <100/min were associated with 84 of a total of 608 episodes of apnoea 10-14 seconds' duration, with 21 of 37 episodes of 15-19 seconds, and with 15 of 15≥20 seconds. One preterm infant with a maximum apnoeic episode of 52 seconds had an associated bradycardia of 27/min.

Three of 5 `near-miss' cot death infants and one preterm infant with a family history of cot death studied immediately before discharge showed prolonged apnoea >40 seconds, or extreme bradycardia <50/min, or both.

Finally, 11 infants with arrhythmias on a standard ECG were studied. Of these, 6 with premature beats and 3 of 5 with episodes of bradycardia did not exhibit apnoea during arrhythmias. Two of the 5 babies with bradycardia however, demonstrated associated apnoea of 10-14 seconds.

There may be a relationship between latent episodes of prolonged apnoea and bradycardia and hypoxaemic brain damage or sudden infant death.