Physiological responses of the newborn infant to resuscitation

Abstract

Endotracheal intubation and IPPV have for many years been the standard methods of resuscitating severely asphyxiated newborn infants. The aim is to expand and ventilate the lungs and to stimulate the infant into spontaneous respiration. Few attempts have been made to evaluate this technique or to study its effects on the neonate. Cross et al. (1960) showed that lung inflation in the neonatal period often produces reflex inspiratory efforts - such as, Head's paradoxical reflex. However, Hull (1969) demonstrated that during resuscitation the most common initial response to lung inflation is a reflex expiratory effort. Pressure and volume studies on isolated newborn lung preparations have demonstrated an 'opening pressure' which has to be exceeded in order to expand the lung (Agostini, 1959; Gribetz et al., 1959; Craig, 1963; Gruenwald, 1963; Rosen and Laurence, 1965). However, Karlberg showed that some spontaneously breathing babies are able to expand their lungs with a small opening pressure (Karlberg and Koch, 1962, Karlberg et al. 1962). More recently, Milner and Saunders (1977) showed that this is the most common pattern of lung expansion at birth. We therefore wanted to study the response of the newborn infant to resuscitation and to find out if an opening pressure was exhibited in the lungs of babies requiring resuscitation. Lung ventilation, endotracheal, and intraoesophageal pressures were measured during standard resuscitation of 20 asphyxiated babies born by caesarean section. The most common response to resuscitation was the production of a large positive intraoesophageal pressure. An opening pressure >2.0 kPa was required to expand the lungs of most of these babies. The need for resuscitation was associated with prolonged maternal anaesthesia before delivery.