Continuous distribution of specific tidal volume throughout the lung

Abstract

An analytical method is presented which, applied to nitrogen washout data from the lung, describes a continuous distribution of specific tidal volume (or ventilation) throughout the air phase of the lung. The technique of computation is described in some detail. Curves of distribution of specific tidal volume are studied for 12 washout data from normal subjects and for 20 washout data from patients with pulmonary emphysema. In normal subjects the pattern of continuous distribution is an asymmetrical one in which the function starts at zero or very nearly so, increases continuously until it reaches a maximum value, then decreases progressively and becomes negligible for comparatively high values of the specific tidal volume. The formulation expressing this law of distribution is neither that of a normal frequency distribution nor that of a log normal one. With increasing over-all tidal volume in normal subjects the curve is progressively displaced toward the right. In contrast, in pulmonary obstructive diseases the maximum amplitude takes place for very low values of the specific tidal volume and tends to vanish slowly toward values that are higher than in the normal subjects. apparent volume of lung Submitted on June 20, 1963