Ventilation-perfusion changes after aerosolized isoproterenol in asthma.

Abstract

Twenty-one patients were studied during a symptomatic episode of asthma before and after treatment with aerosolized isoproterenol. From measurements of arterial blood gases, total ventilation, and alveolar ventilation, alveolar-arterial oxygen gradients (AaPo2) and wasted ventilation ratios were calculated. Airway resistance and dynamic compliance were measured during tidal breathing. Of the 17 patients who responded to treatment by a decrease in resistance, 9 experienced an increase in the AaPo2 (≥ 5 mm Hg) mainly as a result of a decrease in arterial oxygen tension within ten minutes. By 30 minutes, the AaPo2 had returned toward pretreatment values, whereas the resistance remained decreased. These 9 patients had higher initial arterial oxygen tensions than did the 8 patients who did not have an increase in hypoxemia after treatment. It was concluded that increases in hypoxemia after aerosolized isoproterenol therapy for asthma are caused by worsening of ventilation-perfusion relationships, occur mainly ...