2009 OPEN FORUM Abstracts
CHARACTERIZATION OF THE HFA PMDI AEROSOL PLUME BY HIGH SPEED PHOTOGRAPHY
Dirk von Hollen, Kurt Nikander; Respiratory Drug Delivery, Philips Respironics, Parsippany, NJ
The recent transition in pressurized metered dose inhalers (pMDIs) from chlorofluorocarbon (CFC) based propellants to newer hydrofluoroalkane (HFA) propellants has lead to significant changes in aerosol plume characteristics. We used high speed photographic methods to characterize the free air aerosol plume formation of two HFA pMDIs. A pMDI actuator was placed on a clear block with a ruler running away from the actuator in the direction of plume formation. A reflective strip was placed below the ruler, and a 600 watt light source above and behind the axis of plume formation, along with a 300 watt light source at the end of the ruler (Figure 1a). The camera (Casio Exilim Pro EX-F1, Casio America, Inc., Dover, NJ) was placed 3.05-3.66 m perpendicular to the ruler and focused to 85-120 mm from the ruler. [Figure 1] The two albuterol sulfate pMDIs (ProAir HFA, Teva Specialty Pharmaceuticals LLC, Horsham, PA and Proventil, Schering Corp., Kenilworth, NJ) were primed before 1st use, and shaken before each actuation. Upon actuation the camera was triggered, and 60 photos were taken during 1 s. Each pMDI was tested in triplicate. The photos were analyzed, and a marker line added to the image to denote the leading edge of the aerosol plume. The leading edge was defined as the point at which aerosol was visually detected on the photo. The velocity of the leading edge was also calculated at different timepoints. The photos showed that aerosols from both pMDIs were ejected at high velocity (Figure 1b & 1c). The plumes were seen to have a âjet’ phase early on, followed by a âcloud’ phase as the aerosol slowed. The plume leading edge for ProAir was 254 mm from the pMDI at 0.1 s and 460 mm at 0.3 s, and for Proventil was 223 mm at 0.1 s and 394 mm at 0.3 s. The plume leading edge mean velocity for ProAir was 2.47 m/s between 0.016 s and 0.1 s, and 0.9 m/s between 0.2 s to 0.3 s. For Proventil it was 1.98 m/s between 0.016 s and 0.1 s, and 0.74 m/s between 0.2 s to 0.3 s. The method described above provides information on the shape and velocity of aerosol plumes in free air. This method could be extended to provide information on pMDI aerosol plume formation inside a Valved Holding Chamber (VHC), which might help in the optimization of future VHC designs. Sponsored Research - The authors are employees of Philips Respironics, which has supported this study by allowing authors to devote time and resources to its execution and publication.