Thoracic Gas Volume in Infancy

NORMAL values for the end-expiratory thoracic gas volume (TGVr, measured by the plethysmographic method) are available for newborn infants1-4as are values for its ventilated portion, the functional residual capacity (FRC), determined by dilutional methods. TGVrand FRC are considered to be the same in normal subjects. There appears to be only one recent study on the TGVrwhich attempts to fill the gap in time between the young infant and older child. Although the measurement of TGVror FRC is of only limited value in the diagnosis of lung disease in infants, knowledge of the normal values for TGVrthroughout the age range from birth to adulthood may aid our understanding of the geometric dimensions of the lung and its units and thus has mechanical significance. The TGVrof newborns is low when compared with adults on the basis of body surface