Compliance of Lung During First Week of Life

Pulmonary compliance has been defined by respiratory physiologists as the ratio of volume change to change in intrapleural pressure between points of no air flow (i.e., between the beginning and end of inspiration).* It is a mechanical characteristic of the lung and tells one roughly the volume change to be expected in a given lung when a unit pressure difference across the lung is developed by the muscles of respiration under static conditions. Compliance has been shown to be reduced in such clinical conditions as pulmonary fibrosis and congestive heart failure in adults, 1 while a publication from this laboratory described a reduced compliance in newborn infants who had developed clinical signs of respiratory distress. 2 In these conditions, a pathological process has decreased the expansibility of the lung per unit of force applied. The purpose of this report is to present a new technique for measuring tidal volumes and