To assess responses to central and obstructive apnea, we performed 10-hour polygraphic recordings in healthy 33-34 wGA infants. Each apnea period was paired with a control period. The presence of body movements (BM) and augmented breaths (AB), the EEG, heart rate (HR), respiratory rate, phase relationships between thoracic and abdominal respiratory movements, and changes in SaO(2) were evaluated. No apnea caused awakening. Apnea were not usually followed by motor events (no significant differences with control periods), with the exception of most obstructive apnea longer than 10 s. The mean percentage of changes following apnea, normalized to baseline values, was significant for the EEG (frequency slightly increased, mainly after obstructive apnea), HR (deceleration), and respiratory rate (increased). However, the mean values masked heterogeneity across apnea in the direction of the change in each parameter. The only significant correlation was between changes in HR and SaO(2). The increases in EEG frequency and respiratory rate seen in our study can be considered markers of CNS activation, but were small and inconsistent. The heart rate decelerations and SaO(2) changes are not activation markers. Thus, mechanisms underlying restarting of breathing efforts following apnea remain unclear in premature babies. Our investigation establishes the importance of using control data to distinguish between spontaneous and apnea-related events.
Copyright 2000 S. Karger AG, Basel