The effects of an ultrasonic aerosol on pulmonary mechanics and arterial blood gases in patients with chronic bronchitis.

Spirometric and arterial blood gas measurements were made in 26 patients with chronic bronchitis before and after inhaling an ultrasonic mist of 0.45 per cent sodium chloride solution. A significant decrease in one-second forced expiratory volume (FEV1) and vital capacity (VC) was noted after inhalation of ultrasonic mist for 15 minutes. Thirty per cent of these patients also had a decrease in arterial oxygen tension (PaO2) of 8 mm Hg or more. When a bronchodilator aerosol was inhaled before the ultrasonic mist, decrease in FEV1 and VC was not seen, but a significant decrease in PaO2 was noted. The decrease in PaO2 suggested that an undesirable change occurred in the ventilation-perfusion relationships of the lungs after bronchodilator therapy.