Inhalation of 0.30 ppm nitrogen dioxide potentiates exercise-induced bronchospasm in asthmatics

Epidemiologic studies support an association among elevated levels of nitrogen dioxide (NO2), increased respiratory symptoms, and alterations in lung function. To determine if low level NO2 inhalation potentiates exercise-induced bronchospasm, 15 asthmatic subjects, defined by airway constriction with cold air provocation, inhaled 0.30 ppm (560 µg/m3) NO2 for 30 min. All asthmatics inhaled either air or 0.30 ppm NO2 via a mouthpiece for 20 min at rest followed by 10 min of exercise on a bicycle ergometer at a workload of 300 kpm/min, producing a 3-fold or greater increase in minute ventilation. Our studies showed 72 ± 2 (SE)% deposition of inhaled NO2 at rest and 87 ± 1% deposition with exercise (p < 0.001). Nitrogen dioxide inhalation at rest resulted in no significant change in pulmonary function. Nitrogen dioxide inhalation plus exercise compared to control (air) exposure plus exercise produced significantly greater reductions in FEV1 (p < 0.01) and partial expiratory flow rates at 60% of total lung ca...