Brief apneas and reliable assessment of respiratory instability

Studies of apnea in newborns often disregard the frequent occurrence of brief respiratory pauses during sleep. Several investigators have reported an association between the occurrence of brief apneas and subsequent respiratory dysfunction. The present study was undertaken to determine whether the incidence of brief and long apneas is consistent within the individual neonate. This question was posed separately for active and quiet sleep, in order to compare apnea patterns in these two sleep states. Behavioral states and respiration during sleep were continuously monitored in 27 full-term, normal infants on weeks 1-5 postnatally. The first observation took place in the hospital and lasted 3 hr. The remaining observations were conducted for 7 hr in the home. Respiratory pauses of 2 sec or greater were identified and analyzed in terms of rate per hour, mean length, and longest episode in both quiet and active sleep. The distribution of apnea by duration was analyzed for each sleep state. Apnea rates determined separately for brief pauses (2-5 sec) and episodes of longer duration (6-16 sec) were positively correlated on all observations in both active and quiet sleep. The magnitude of the correlation decreased slightly with age in active sleep, whereas in quiet sleep, the association progressively increased. The implications of these findings for the reliable assessment of respiratory instability in the newborn are discussed.