Profiles of Inhaled Flow from Dry Powder Inhalers in Subjects Unfamiliar with the Devices

The inhalation profile (flow rate, volume and pattern) from a dry powder inhaler (DPI) is crucial for the efficient delivery of medications to the bronchial airways. However, instructions regarding the inhalation profile are not always adequate. We recruited 28 volunteers who were not familiar with DPIs to simulate patients who received the first prescription of a DPI. Following verbal instructions, they inhaled from various DPIs, and we recorded the inhalation profiles as listed above. Flow-time curves were classified into 3 patterns. A: early peak followed by a linear decrement, C: trapezoid, B: between A and C. Mean ( ± SD) peak inhaled flow rates (PIFR) and volumes were 54.3 ± 23.5 L・min-1and 1.40 ± 0.58 L for the Diskus®, 52.8 ± 11.5 and 1.39 ± 0.58 for the Turbuhaler®, and 46.0 ± 13.4 and 1.27 ± 0.74 for the Twisthaler®, respectively. There were weak correlations between PIFRs and inhalation volumes. Percent of subjects attaining a PIFR > 30 L・min-1 was 92.9% (Diskus®), 92.9% (Turbuhaler®), and 100% (Twisthaler®), and those attaining a PIFR > 60 L・min-1 were 32.2% (Diskus®), 17.9% (Turbuhaler®), and 14.3% (Twisthaler®). Only a few subjects inhaled with pattern A, and most of the subjects inhaled with pattern C. In conclusion, untrained patients may inhale with suboptimal flow rates and volumes from a DPI. Inhaled flow patterns may also be poor.