Respiratory pauses in normal prematurely born infants. A comparison with full-term newborns

To assess the influence of gestational age (GA) and sleep states on respiratory pauses (RP), apnea index (AI) and periodic breathing (PB), we made polygraphic recordings on 40 normal newborns with GA of 31-41 weeks. Only 2 out of a total of 2,406 RP were obstructive. We never recorded greater than 15-second duration central RP. 10-15 s RP were rare, 2% of the total number observed in newborns with a GA of 31-38 weeks. Selective flattening of thoracic respiratory movements (while abdominal and nasal respirations persisted) were observed in all age-groups. In all GA groups, RP frequency, AI and percent of PB were significantly higher in active sleep, compared to quiet sleep. In indeterminate sleep, values were intermediate. RP frequency and AI were high in newborns with GA of up to 38 weeks; they decreased significantly only at GA of 39-41 weeks; i.e. according to RP criteria, newborns with a GA of 37-38 weeks were similar to prematures, but not to 39- to 41-week GA newborns. There were no significant differences between twins and singletons. We did not find significant correlations between RP incidence on one hand and respiratory rate or out-of-phase occurrence of thoracic and abdominal respiratory movements in the other. 17% of RP occurred after gross body movements.