VENTILATORY FUNCTION TESTS. II. FACTORS AFFECTING THE VOLUNTARY VENTILATION CAPACITY

Abstract

Procedures, reliability of measurement, and normal values are reported for vital capacity, maximum expiratory pressure, and capacity ratio (ratio of ventilation to vital capacities). The ventilation capacity correlated weakly with vital capacity and not at all with max. expiratory pressure in normal subjects. Exptl. impairment of vital capacity reduced ventilation capacity in proportion. Exptl. increase in air-flow resistance profoundly reduced ventilation capacity, but not the vital capacity. A scheme is presented for analyzing the causes of impaired ventilation capacity in terms of size, force, and resistance of the pulmonary bellows.