Background: Inhaler technique and spray characteristics are critical for adequate management of asthma symptoms with pressurized metered-dose inhalers (pMDIs). A lower spray force has been directly associated with a decrease in throat deposition of asthma medication, and a higher spray temperature may alleviate the "cold Freon effect" associated with pMDIs. The objective of the study was to characterize and compare the temperature, maximum spray force, and duration of the emitted plume from two pMDIs: ProAir(®) hydrofluoroalkane (HFA) and Ventolin(®) HFA.
Methods: A spray force tester model SFT1000 and thermocouple were used to test 10 units from three separate lots (total of 30 units) of each inhaler type. Three consecutive actuations were tested at a spray distance of 40 mm from the edge of the mouthpiece. Room temperature, humidity, and initial weight of the pMDI were recorded. Final weight of each pMDI was recorded to determine the spray weight of individual actuations. pMDIs were primed and operated according to instructions provided in the package insert. Aerodynamic particle size distribution (APSD) was also assessed using a next-generation impactor at a flow rate of 28.3 L/min.
Results: Measurements were obtained from three consecutive actuations for each of 30 units of ProAir(®) HFA and Ventolin(®) HFA (10 units from three separate lots), resulting in a total of 90 actuations tested for each pMDI. Minimum plume temperatures recorded were 7.2 ± 0.7°C and -35.9 ± 12.7°C, respectively, for ProAir(®) HFA and Ventolin(®) HFA. ProAir(®) HFA produced more than a twofold greater plume duration (385 ± 46 ms vs. 156 ± 58 ms; p<0.001) and a significantly lower mean maximum spray force (33.6 ± 11.4 mN vs. 75.9 ± 12.0 mN; p<0.0001) compared with Ventolin(®) HFA. APSD analysis demonstrated that ProAir(®) HFA produced almost twice as much fine particle (<5 μm) dose with lower geometric standard deviation, compared with Ventolin(®) HFA. Two inhalers produced similar mass median aerodynamic diameters, ranging from 2.3 to 2.4 μm.
Conclusions: The ProAir(®) HFA delivers a warmer, lower-impact, and longer-lasting plume compared with Ventolin(®) HFA, which may provide a more consistent, comfortable experience for patients using a pMDI. ProAir(®) HFA produces higher fine particle dose than Ventolin(®) HFA.