Bronchodilator response in patients with persistent allergic asthma could not predict airway hyperresponsiveness

Abstract

: Anticholinergics, or specific antimuscarinic agents, by inhibition of muscarinic receptors cause bronchodilatation, which might correlate with activation of these receptors by the muscarinic agonist methacholine. The aim of this study was to determine whether a positive bronchodilator response to the anticholinergic ipratropium bromide could predict airway hyperresponsiveness in patients with persistent allergic asthma. The study comprised 40 patients with mild and moderate persistent allergic asthma. Diagnosis was established by clinical and functional follow-up (skin-prick test, spirometry, bronchodilator tests with salbutamol and ipratropium bromide, and methacholine challenge testing). The bronchodilator response was positive to both bronchodilator drugs in all patients. After salbutamol inhalation, forced expiratory volume in 1 second (FEV1) increased by 18.39 +/- 6.18%, p < .01, whereas after ipratropium bromide, FEV1 increased by 19.14 +/- 6.74%, p < .01. The mean value of FEV1 decreased by 25.75 +/- 5.16%, p < .01 after methacholine (PC20 FEV1 [provocative concentration of methacholine that results in a 20% fall in FEV1] from 0.026 to 1.914 mg/mL). Using linear regression, between methacholine challenge testing and bronchodilator response to salbutamol, a positive, weak, and stastistically significant correlation for FEV1 was found (p < .05). Correlations between methacholine challenge testing and the bronchodilator response to ipratropium bromide were positive and weak but not statistically significant. The positive bronchodilator response to ipratropium bromide could not predict airway hyperresponsiveness.

Figure 1

A, Scatterplot diagram of the percent change in forced expiratory volume in 1 second (FEV₁) after inhalation of ipratropium bromide versus the natural logarithm of PC₂₀FEV₁ (provocative concentration of methacholine that results in a 20% fall in FEV₁) for methacholine challenge (r = .169, p > .05). B, Scatterplot diagram of the percent change in FEV₁ after inhalation of salbutamol versus the natural logarithm of PC₂₀FEV₁ for methacholine challenge (r = .314, p = .049). Dashed lines represent the 95% confidence interval for linear regression.