Flow-volume loops in newborn infants.

Flow-volume loops were obtained during the performance of crying vital capacity (CVC) maneuvers in 31 infants, 18 of whom had hyaline membrane disease (HMD). Both healthy and distressed infants had flow-volume loops resembling those found in adults with variable intrathoracic obstruction of the central airways. Flow rates during inspiration and expiration increased as the CVC increased. Infants with HMD had narrower inspiratory loops and attained peak expiratory flow later than nondistressed infants, but these differences were not statistically significant. Vocalizations, loss of lung recoil associated with loss of lung volume, and partial collapse of intrathoracic airways may all contribute to the shape of the flow-volume loop in infants.