Breathing patterns and heart rates at ages 6 weeks and 2 years
C. F. Poets, V. A. Stebbens, J. R. Alexander and D. P. Southall
Department of Pediatrics, National Heart & Lung Institute, London, England.
Forty-two randomly selected, full-term, healthy infants underwent 24-hour
electrocardiographic recordings and breathing movements at about ages 6
weeks (median age, 43 days; range, 34 to 61 days) and 2 years (median age,
26 months; range, 21 to 35 months). The number and duration of apneic
pauses of 3.6 seconds or longer were analyzed. Periodic apnea was defined
as a sequence of three or more apneic pauses, each separated by fewer than
20 breaths. All other apneic pauses were defined as isolated. Median heart
rates and respiratory rates, which were measured during regular breathing,
decreased from 137/min and 35/min to 98/min and 21/min, respectively. The
total duration of periodic apnea remained unchanged (median, 0.06 min/h vs
0.05 min/h). Although the median frequency of all isolated apneic pauses
decreased from 3.6/h to 2.5/h, the number of those that were longer than 6
seconds increased from 0.37/h to 0.80/h, leading to an increase in the
proportion of these pauses, among all isolated apneic pauses, from 10% at
age 6 weeks to 32% at age 2 years. Only one apneic pause in one infant at
age 6 weeks, but eight pauses in six children at age 2 years, were longer
than 15 seconds. A knowledge of such normal variability in the duration of
apneic pauses in older infants and young children is essential for the
interpretation of pneumograms and alarms while monitoring breathing
movements.
