Relationship between anatomic dead space and body size in health, asthma, and cystic fibrosis.

Abstract

Anatomic dead space was measured in 19 healthy adults, 27 healthy children, 22 asthmatic children, and 11 children with cystic fibrosis. Anatomic dead space varied as the 2.92 power of height, 1.40 power of body surface area, 0.86 power of weight, and 0.8 power of functional residual capacity in healthy subjects seven years to 40 years of age. Extrapolation of the regression equations adequately predicted anatomic dead space values previously reported for neonates. It was concluded that there is a constant relationship of airway volume to parameters of body size throughout life that conforms to the expected volume changes of a growing mass. All values of anatomic dead space in children with asthma and cystic fibrosis fell within the 95 per cent confidence limits of the correlations for healthy subjects. The wide range of anatomic dead space values about the regression lines introduced errors in alveolar gas tensions calculated from estimates of anatomic dead space.