Peak inspiratory flow rate and slope of the inhalation profiles in dry powder inhalers

Aerosol delivery depends on device design and inhalation technique. In vitro device evaluations have shown that the emitted dose and fine particle mass of dry powder inhalers (DPIs) increase at high peak inspiratory flow rates (PIFR). Since the PIFR is mostly achieved after the release of the powder, slope of the pressure profile is also described as an important determinant. The aim of the present study was to assess whether the PIFR while using Diskus it and Turbuhaler it inhalers could be used to predict the slope of the inhalation pressure profile. In a group of 10 stable asthma patients and three groups (mild, moderate and severe) of 16 chronic obstructive pulmonary disease (COPD) patients, lung function was measured, and for each device, 18 inhalation profiles were recorded with the inhalation profile recorder during six sessions over 10 weeks. The values for the pressure slope and PIFR of both Diskus and Turbuhaler, were significantly correlated. The r-values were 0.865 and 0.882, respectively (p