The Relationship Between Airway Resistance, Airway Conductance and Lung Volume in Subjects of Different Age and Body Size12

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Abstract
Measurements of airway resistance and lung volume were made using a body plethysmograph method on 26 normal subjects of both sexes, with age ranging from 4 to 87 years. In each subject studies were made at different degrees of lung inflation. Airway conductance, the reciprocal of resistance, was approximately linearly related to the degree of inflation as follows: Conductance = 0.24 x Volume, the units being liters, cm H2O, and seconds. Regressions are given for children, women and men. Airway resistance in children is 3 to 5 times that for adults. This is related more to differences in lung volume than to differences in age. A method is suggested for correcting changes in airway resistance for concomitant changes in lung volume during studies on airway resistance. Theoretical considerations suggest that the small airways in which resistance to flow is located may be as distensible as the lung as a whole. A simplified method for predicting normal limits for airway conductance at different lung volumes is given.