Does the inhalation device affect the bronchodilatory dose response curve of salbutamol in asthma and chronic obstructive pulmonary disease patients?

Abstract

This open randomized study examined differences between the effects of an equal dose of salbutamol administered via the Diskus, Turbuhaler, and pMDI plus Volumatic. Measurements included dose response curves, dynamic and static lung volumes, respiratory muscle strength, and systemic effects.
The cumulative dose-response study compared the biological effects (pulmonary function, respiratory muscle function, systemic effects) of an equal dose of salbutamol delivered via four different devices in 23 patients with asthma and 21 patients with moderate or severe chronic obstructive pulmonary disease (COPD).
Salbutamol via Volumatic showed significantly better bronchodilation than via pMDI or Turbuhaler in both patient groups. No significant difference was found between salbutamol via Volumatic and Diskus. However, the advantage of Volumatic is of marginal clinical relevance since the additional bronchodilation was a maximum of 140 ml FEV(1) and did not exceed the minimal patient-perceivable improvement. In the asthma group a more evident plasma K(+) decrease was found after salbutamol delivered via pMDI and pMDI plus Volumatic. Furthermore, especially in the COPD patients a significant decrease was observed in hyperinflation and consequently an improvement in maximal inspiratory pressure as a result of salbutamol via all devices.
Bronchodilation by salbutamol was slightly more effective via Volumatic than via pMDI or Turbuhaler. No significant difference in bronchodilation was found between salbutamol via Volumatic and Diskus. The advantage of Volumatic is not of clinical relevance.