Introduction and Objectives Impulse oscillometry (IOS) is known to be a sensitive marker of airway dysfunction, but is commonly associated with a wider variation than spirometry. The effects of β-blocker induced bronchoconstriction on IOS have not been studied. We compared the sensitivities of IOS and spirometry in the assessment of bronchoconstriction to propranolol and bronchodilatation to salbutamol.

Methods Mild-to-moderate persistent stable asthmatics taking =1000 μg day budesonide or equivalent, received a single dose of 10 mg or 20 mg of oral propranolol followed by histamine bronchial challenge testing (PC10), with recovery to nebulised salbutamol (5 mg). Spirometry and IOS were measured pre and 2-h post β-blocker, post histamine and 20 min post salbutamol. Pre vs post % change (95% CI) values were compared and standardised response means (SRM) were calculated to assess the “signal to noise” of each test.

Results Thirteen patients (mean age, 34 years) completed per protocol: 11 received 20 mg of oral propranolol. All IOS indices showed a greater magnitude of response to propranolol (ie, as % change) compared to spirometry. After adjustment for test variability, in response to propranolol, SRM's for IOS outcomes were better than spirometry with the highest seen with R5 and fres. Likewise for the bronchodilator response to salbutamol the highest SRMs were also seen with R5 and fres (see Abstract S8 table 1).

Conclusions IOS is a more sensitive response outcome than spirometry with respect to bronchoconstriction to oral propranolol and bronchodilatation post salbutamol in mild-to-moderate asthmatics.