An assessment of methacholine inhalation tests in elderly asthmatics

We have assessed the feasibility and value of measuring nonspecific bronchial responsiveness to methacholine in investigation of asthma in the elderly. Results from duplicated tests in 20 subjects aged 65-82 years were expressed as dose provoking a 20% decrement in 1 second forced expiratory volume (PD20.FEV1) or peak expiratory flow (PD20.PEF). Repeatability for PD20.FEV1 was satisfactory but less good than in younger subjects, 95% confidence limits being 0.39-2.57 and 0.52-1.91, respectively, x initial PD20. For PD20.PEF, confidence limits were wider (0.26-3.91 x initial PD20) but multiple PEF measurements were better tolerated than those of FEV1, which commonly caused fatigue and dizziness. PD20.FEV1 and PD20.PEF correlated closely (r = 0.95, P less than 0.0001) and both predicted bronchodilatation following a 6-week course of inhaled corticosteroid and beta agonist. This was not predicted by the response to a single dose of beta agonist. We conclude that measurement of bronchial responsiveness is feasible and clinically valuable in elderly subjects.