The Effect of Acid Aerosols on Airway Responsiveness in Asthmatics

Abstract

ABSTRACT

Most investigations have shown that short-term exposure to acid aerosols did not cause airway obstruction in normal subjects at concentrations up to 1 mg/m³, whereas some studies could demonstrate adverse effects in asthmatic subjects at concentrations of 0.1 mg/m³ or higher. Inhalation of acid aerosols may produce airway hyperreactivity to carbachol in normal subjects and may enhance airway hyperreactivity in asthmatic subjects. We investigated 12 patients with bronchial asthma inhaling aerosols of either saline (S), ammonium sulfate (AS), or sulfuric acid (SA). Two inhalations of 10 min were performed 30 min apart. Thirty minutes later, a hyperventilation challenge with 0.75 ppm SO₂ was performed. We determined the ventilation rate necessary to increase SRaw by 100%, PV₁₀₀SRaw, by stepwise increasing ventilation. The response showed large variation after AS and SA, with no significant differences between the first and the second inhalation. SRaw was significantly increased after AS. Mean PV₁₀₀SRaw did not differ between S, AS, and SA. In a second experiment we investigated in 6 patients with bronchial asthma the effect of short-term inhalation of ammonium nitrate aerosol. We did not observe an effect of nitrate aerosol of airway responsiveness to sulfur dioxide. From these data we conclude that in patients with mild asthma short-term inhalation of sulfate aerosols produces small effects on lung function, no refractoriness, and no change of bronchial responsiveness to hyperventilation of SO₂. In addition, short-term inhalation of ammonium nitrate aerosol does not affect bronchial responsiveness to sulfur dioxide.