Pressure and inspiratory flow characteristics of dry powder inhalers

Abstract

This study compared inspiratory characteristics of the Novolizer ® and Turbuhaler ®. Sixty patients with obstructive lung disease (40 asthmatics, 20 patients with COPD) and without DPI experience were enrolled into this investigator initiated, randomized, cross-over study. Collected data of 56 patients were eligible for analysis. Inspiratory pressure and inspiratory flow through both devices were measured in every patient using a double-beam oscilloscope. Peak inspiratory flow (PIF), duration of inspiratory flow >60 l/min and increase in inspiratory pressure were significantly higher in the Novolizer ® group. In addition, the inspiratory flow rate 0.1 s after beginning of inhalation was over two-times higher at inhalation through the Novolizer ® compared to inhalation through the Turbuhaler ®. The Turbuhaler ® data, but not the Novolizer ® data, showed a significant negative correlation between lung function and inspiratory flow. The dynamic resistance of the Turbuhaler ® was 5.5-times higher than that of the Novolizer ®. Patients using the Turbuhaler ® had to invest a significantly higher inspiratory effort compared to the use of the Novolizer ® in order to achieve the same inspiratory flow (e.g., 60 l/min). Indeed, more than 40% of the patients in the Turbuhaler ® group failed to reach an inspiratory flow of 60 l/min. Overall, patients inhaling through the Novolizer ® had a better inhalation performance than those inhaling through the Turbuhaler ®.