Effect of posture on bronchial reactivity to inhaled methacholine in patients with mitral valve stenosis

To compare the effects of posture on bronchial reactivity in 12 patients with mitral valve stenosis (MS) and 10 with bronchial asthma (BA), a methacholine inhalation test was performed 2 h after being in either a supine or sitting position. All patients showed bronchial hyperreactivity to inhaled methacholine before the study. In MS patients, logarithmic values of the cumulative dose producing a 35 percent decrease in respiratory conductance (log PD35Grs) were significantly lower 2 h after being in a supine position than in those after being in a sitting position (0.71 +/- 0.78, 1.02 +/- 0.53 log units, respectively, p < 0.05). In BA patients, however, log PD35Grs did not show significant changes (0.42 +/- 0.51, 0.58 +/- 0.48 log units, respectively). Variables of pulmonary function tests showed no significant differences between the two positions in both patients with MS and BA. We conclude that the bronchial hyperreactivity in MS is enhanced after the supine position for 2 h and that the supine posture may play an important role in the pathogenesis of cardiac asthma.