Relation Between Mechanics of Respiration, Lung Size and Body Size From Birth to Young Adulthood

¹ From the Department of Pediatrics, Harvard Medical School, and the Department of Medicine of the Children's Medical Center, Boston, Massachusetts

Data on the mechanics of respiration and lung and body size have been related for newborn infants, children between the ages of 5 and 17, and young adults. Simultaneous measurements of tidal volume and intra-esophageal pressure changes have been used for the calculation of compliance and flow resistance. Lung weights, predicted on the basis of height, functional residual capacity and vital capacity all served as indexes of lung size. During the period of extrauterine growth the lung compliance-lung volume relationship was relatively constant, averaging .057 ml/cm H₂O/ml FRC and .035 ml/cm H₂O/ml VC. The compliance-predicted lung weight relationship was also relatively constant, with the exception of newborn infants whose values were half that of older subjects. Functional residual capacity was found to be related to height^2.86 throughout this range of body sizes. Flow resistance decreased with increases in body and lung size but no simple relationship could be found.