Depression of Respiratory Muscles and Defective Responses to Nasal Obstruction during Active Sleep in the Newborn

Abstract

Henderson‐Smart, D. J. and Read, D. J. C. (1976). Aust. paediat. J. , 12, 261–266. Depression of respiratory muscles and defective responses to nasal obstruction during active sleep in the newborn. Rib‐cage and abdominal movements were recorded during different sleep stages in 22 healthy babies at ages up to 3 months and in 8 older infants up to 10 months. During active sleep, all babies and 6 infants developed: (i) rib‐cage collapse during diaphragmatic descent; (ii) overall deflation of the rib‐cage. Oesophageal pressure recordings in 7 babies showed that this paradoxical rib‐cage motion was not accompanied by increased negativity of intra‐pleural pressure, and was therefore not due to intermittent airway obstruction. In 7 newborn lambs, the development of rib‐cage paradox during active sleep was related to a marked reduction of the electromyographic (EMG) activity of intercostal and abdominal muscles. During quiet sleep, nasal occlusion initiated a strong reflex augmentation of intercostal EMG activity and prompt arousal, whereas in active sleep these defensive responses were absent. A reduction of pulmonary O 2 ‐stores and ventilation may result during active sleep, making the newborn baby vulnerable to a rapid development of hypoxaemia, respiratory depression and sudden infant death (crib‐death).