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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

The ventilatory response of six subjects to increasing levels of alveolar CO2 was measured at rest and during the hyperventilation induced by passive vibratory movements of the whole body. During vibration, addition of CO2 to the inspired air produced no increase in ventilation until the PaCOCO2 reached a critical level which coincided closely with the intersection of the vibration with the resting CO2 response curve. Above this level the vibration curve was almost superimposed on the resting one. There was no evidence of an additive effect of the two stimuli, and no increase in sensitivity to CO2 during vibration. In these respects the situation differs from that in which CO2 is combined with hypoxia or hyperthermia. The findings indicate that when respiration is stimulated by vibration and CO2 simultaneously, the resultant ventilation at any point is solely that produced by the stronger of the two stimuli. hyperventilation; PaCOCO2 and ventilation; CO2 response curve and vibration Submitted on July 30, 1964

No abstract