Controlled exposure of volunteers with chronic obstructive pulmonary disease to nitrogen dioxide

Twenty-two volunteers with chronic obstructive pulmonary disease were exposed to nitrogen dioxide at 0.0, 0.5, 1.0, and 2.0 ppm in a controlled environment chamber. Exposure lasted 1 hr and included two 15-min exercise periods, during which the mean ventilation rate was roughly 16 L/min. Pulmonary mechanical function was evaluated pre-exposure, after initial exercise, and at the end of exposure. Blood oxygenation was measured by ear oximetry pre-exposure and during the second exposure period. Symptoms were recorded during exposures and for 1-wk periods afterward. No statistically significant changes in symptom reporting could be attributed to nitrogen dioxide exposure at any concentration, compared to the 0.0 ppm control condition. Measures of pulmonary mechanics showed either no significant changes, or small and equivocal changes. Arterial oxygen saturation showed marginal improvement with exercise, regardless of nitrogen dioxide concentration.