EFFECT OF LOW CONCENTRATIONS OF OZONE ON PULMONARY FUNCTION IN MAN

Eleven subjects in sixteen experiments breathed 0.6–0.8 ppm of ozone through a mouthpiece for 2-hr periods. Measurements of pulmonary function were made immediately before and after each experiment. The changes were compared with those observed after a control experiment in which air was breathed through the same circuit for a similar period. In this concentration, ozone was found to produce a highly significant reduction in steady-state D1CO of 5.4 ml CO/min mm Hg, a change about four times larger than that of the air control experiments. The vital capacity, FEV0.75 x 40, and maximal midexpiratory flow rate decreased by about 10% after ozone breathing, the change being statistically significant in the first two of these only. Gas distribution, and dynamic and static pulmonary compliance were measured in two subjects and were not affected by ozone. Thickening of the alveolar wall by edema fluid is suggested as the most likely explanation of the fall in D1CO that has been observed. The vital capacity and expiratory flow rates may be limited in part by tracheobronchial irritation that follows inhalation of 0.6 ppm of ozone for 2 hr.

diffusing capacity after breathing ozone; lungs, effect of ozone; pulmonary function after breathing ozone

Submitted on September 23, 1963

ALVEOLAR-ARTERIAL OXYGEN GRADIENT IN ANDEAN NATIVES AT HIGH ALTITUDE

The A-a Do2 (alveolar-arterial oxygen tension difference) was determined at three levels of oxygenation in three groups of subjects: 1) normal persons at sea level, 2) normal Andean natives at high altitude, 3) Andean natives with chronic mountain sickness. The values of A-a Do2 in the Andean natives were uniformly higher than in normal sea-level residents at all levels of oxygenation. These findings were accentuated in patients with chronic mountain sickness. It is concluded that there is no decrease in diffusion barrier for oxygen, and there may be increased veno-arterial shunting in the lung and wider distribution of ventilation-perfusion ratios in the high-altitude residents than in normal subjects at sea level; and that part, at least, of the condition of chronic mountain sickness is an accentuation of these changes.

tissue hypoxia; acclimatization; chronic mountain sickness; secondary polycythemia; pulmonary O2 diffusion barrier; pulmonary veno-arterial shunt; pulmonary ventilation perfusion ratio

Submitted on April 3, 1963