An "electronic lung" in the stud Y of pulmonary function

Abstract

A mathematical model of the lung, consisting of two regions and a common dead space, is described. An analog computer is used to solve the equations of this model. Two examples are given. In the first, curves of the mixing of an inert gas and the absorption of carbon monoxide obtained in emphysema patients are analyzed. Such curves were the result, in terms of our model, of a small, well-ventilated region with a low diffusing capacity and a large poorly ventilated region having most of the diffusing capacity of the lung. The computer model is modified and used to predict the effects on inert gas washout of ventilating the lung in various sequences. The slowest washout is obtained when the poorly ventilated region filled first and emptied last, the most rapid when this region filled last and emptied last. Sequential ventilation alone can produce relatively minor delays in inert gas washout. Error in estimating reg ional ventilation from inert gas washout is small when the poorly ventilated region fills first and empties last, but appreciable when this region fills last and empties last.