Peak inspiratory flow via Easyhaler dry powder inhaler in adults before methacholine challenge test and during bronchoconstriction

Sufficient peak inspiratory flow (PIF) is needed for efficient drug delivery from dry powder inhalers. 99% of patients with asthma and COPD have been reported to achieve required 30 L/min with Easyhaler (EH), but there is limited data available during acute bronchoconstriction. Our aim was to study if patients achieve sufficient PIF via EH during bronchoconstriction. Data was collected as part of a randomised clinical trial (<ext-link>NCT05084222</ext-link>). Participants who had ≥20% drop in FEV₁ in methacholine challenge (MC) test were included. Inspiratory flow profiles via EH (Salbutamol EH or Budesonide-formoterol EH) were recorded before the test and during reliever dosing with EH connected to a spirometer. 68% of the participants (N=120) were females, mean age 45 y (range 18-80) and FEV₁ % pred. 88.7% (62-142). All participants achieved PIF of ≥30 L/min before MC test. During bronchoconstriction the proportion was 97% in Salbutamol EH group and 100% in Budesonide-formoterol EH group. There was only a small difference in mean (SD) PIF via Salbutamol EH (mono inhaler) before the test and during bronchoconstriction (53 L/min [9.4] and 51 L/min [10.5]). PIF via Budesonide-formoterol EH (combi inhaler) was 66 L/min (12.0) and 60 L/min (13.5), respectively. Inspiratory volumes were 2.04 L (0.85) before test and 2.00 L (0.73) during bronchoconstriction for Salbutamol EH, and 2.34 L (0.78) and 2.21 L (0.77), for Budesonide-formoterol EH. The study showed that almost all patients can achieve PIF ≥30 L/min via EH during bronchoconstriction. Ability to generate a sufficient inspiratory flow is not limiting the use of EH DPI during acute obstructive event.