In Vitro Comparison of Two Blister-Type Inhalers

BACKGROUND: Ellipta is a respiratory device that is a successor of the Diskus. A major difference between the devices is that Ellipta, especially the 2-strip type, includes a pair of blisters rather than a single blister as contained in Diskus. This study aimed to compare the particle-release properties and mechanical features of both devices. METHODS: A pump was used to evacuate air from each dry powder inhaler (DPI) with either a ramp-up or triangular pattern. The particle release volume and peak inspiratory flow of the DPIs were compared. Then the resistance of each component was measured.RESULTS: Both DPIs required specific threshold flows for particle release. Inspiratory flows exceeding the threshold values (Ellipta 11.3 +/- 4.0 L/min and Diskus 29.7 +/- 4.7 L/min using ramp-up inhalations; Ellipta 10.6 +/- 2.1 L/min and Diskus 28.4 +/- 5.2 L/min using triangular ones) did not further increase particle release volumes. The inspiratory flows required for Ellipta were significantly less than those for Diskus. The particle release volume exceeding threshold flow for Ellipta was approximately 2.62 (ramp-up) and 2.01 (triangular) times those of Diskus. The resistance of one blister was similar (0.44 cm H2O/L/min vs 0.42 cm H2O/L/min for Ellipta and Diskus, respectively). As Ellipta includes 2 parallel blisters, similar resistances suggest that Ellipta requires twice the flow of Diskus. The flow distributions for particle release in Ellipta and Diskus were 35.3 and 5.2% of the total inspiratory flow, respectively.CONCLUSIONS: The Ellipta required lower inspiratory flow than Diskus, which arises from a higher distribution to blister flow. Ellipta may be preferable to Diskus for patients with impaired pulmonary function.