Physiological Approaches to Respiratory Control Mechanisms in Infants

Abstract

We have examined in a group of normal infants and in an "at-risk" group with clinical sleep apnea syndrome the duration and frequency distribution of apneas during sleep. In order to improve the estimation of an apnea factor, we introduced a weighting function which is based on the expected frequency distribution of apnea durations of normal infants. We were able to observe a good agreement between clinical rating, based on anamnestic symptoms, and numerical scoring. All infants of the at-risk group were treated with aminophylline, and the respiratory state improved significantly in nearly all cases. Breathing hypoxic gas mixtures tended to depress respiration, especially in the at-risk group, with a pronounced drop of pO2-values. Investigations on the coordination of respiration, sucking, and swallowing during nutritive sucking demonstrated a correspondence between disturbed coordination ability and the sleep apnea syndrome (SAS). This relationship is interpreted to be a result of an immaturity of the autonomic nervous system. In order to evaluate possible hereditary components in conjunction with respiratory disorders and, possibly, SIDS, we studied siblings of SIDS victims, of near-miss infants, and of infants with SAS. Only siblings of SAS and near-miss infants showed clinical signs of respiratory disorders with a rather high prevalence, whereas most of the siblings of SIDS victims were completely lacking conspicuous respiratory symptoms. Our results suggest that not all infants with sleep apnea syndrome are necessarily at increased risk for SIDS.