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MIXED APNEA OF INFANCY - SIGNIFICANCE OF RESPIRATORY PATTERN

Mixed apnea of infancy is a respiratory pattern characterized by both central and obstructive apnea. In order to characterize this form of apnea more completely, 67 patients were evaluated in the Apnea Screening Program of The Children's Hospital of Philadelphia. These infants had predominantly mixed apnea and represented 8.1% (67/838) of the children evaluated for apnea during a two year period. Mean BW was 1700 ± 88.8 SEM gms, mean GA was 31.6 ± 0.4 SEM wks. The average age at the time of study was 5.8 ± 0.5 SEM wks. Fifty-nine (88%) infants were premature, eight (12%) were term babies with infantile apnea or siblings of SIDS victims. Infants were evaluated for a minimum of 6 hours by thermistor-pneumocardiogram study. 279 episodes of mixed apnea were detected. 217 (77.8%) episodes began as central apnea and progressed to obstructive apnea. 62 episodes (22.2%) initially demonstrated obstructive apnea that subsequently became central. 155 (55.6%) episodes of mixed apnea were accompanied by bradycardia (decrease in heart rate >40 bpm below baseline level). The duration of mixed apneic episodes tended to be prolonged with 85 (30.5%) 10-15 seconds duration, 120 (43%) 15-20 seconds duration, and 74 (26.6%) > 20 seconds duration. Children with predominantly mixed apnea had associated other apnea: 33 (49.3%) had central apnea, 11 (16.4%) obstructive apnea, and 24 (35.8%) had excessive periodic breathing (<5% of sleep). These data suggest that in mixed apnea, central apnea most commonly precedes obstructive apnea. Approximately 70% of episodes of mixed apnea last for longer than 15 seconds. The majority of such episodes have associated bradycardia and therefore represent a significant clinical problem.