STUDIES OF RESPIRATORY INSUFFICIENCY IN NEWBORN INFANTS

Abstract

Serial measurements have been made of the resting tidal and minute volumes and respiratory rates on 40 premature infants during the first 2 weeks after birth. The 40 infants were divided into three groups according to the trend of their respiratory rates. Infants whose respiratory rates were normal from birth (Group I) had the highest mean resting tidal volumes during the first 2 weeks. Mean resting tidal volumes were significantly lower throughout the first week among infants whose respiratory rates were initially high during the first hour and subsequently declined to normal (Group II) and among infants whose respiratory rates significantly increased after the first hour (Group III). Infants in Group III had the lowest tidal volumes and the most severe degrees of respiratory insufficiency. The mean resting tidal volume among infants in Group III was less at the end of the first week than that of infants in Group I at the end of the first day. Although tidal volumes in infants in Group II were in general much lower than normal the first few days after birth, exceptions to this rule may occasionally be encountered. Although all three groups showed an increase in mean tidal volumes of about 25% at the end of 24 hours over the volumes obtained during the first 3 hours after birth, the respiratory rates were different. In Group I the increase in tidal volume was accompanied by no significant change in respiratory rate; in Group II, by a significant decrease in respiratory rate; in Group III, by a significant increase in respiratory arte. During the second day Group III showed clinical improvement accompanied by a significant decrease in mean respiratory rate but not by any significant increase in mean tidal volume. Fluctuations in mean minute volumes in Groups II and III on the first 2 days were largely dependent on changes in respiratory rates.