Cardiorespiratory function.

ACCURATE EVALUATION OF THE DEGREE OF IMPAIRMENT OF PULMONARY FUNCTION IN PERSONS WITH FIBROSIS AND EMPHYSEMA REQUIRES: (1) ventilatory measurements from rapid spirogram tracings (vital capacity, maximal breathing capacity and the time required to blow the air from the lungs); (2) determination of the degree of bronchospasm present; (3) determination of the degree of pulmonary emphysema (residual air expressed quantitatively as percent of total lung volume); (4) determination of the arterial blood oxygen saturation at rest and immediately after step-up exercise; (5) measurement of the oxygen extraction from inspired air (per cent of oxygen removed) during rest and exercise; (6) determination of the oxygen up-take during exercise; and (7) observation of the duration of dyspnea after step-up exercise. No single physiologic test is adequate in evaluating impairment of pulmonary function, and roentgenograms of the chest are unreliable as a sole basis for appraisal of disability. In industrial medicine, pulmonary function studies make possible (a) more accurate diagnosis and evaluation of pulmonary disability; and (b) earlier detection and thus prevention of prolonged exposure by susceptible individuals to environmental hazards.