Use of Computational Fluid Dynamics (CFD) Dispersion Parameters in the Development of a New DPI Actuated with Low Air Volumes

Abstract

Purpose: To determine the predictive power of computational fluid dynamics (CFD)-based dispersion parameters in the development of a new inline DPI that is actuated with low volumes of air.Methods: Four new versions of a dose aerosolization and containment (DAC)-unit DPI were created with varying inlet and outlet orifice sizes and analyzed with results from five previous designs. A concurrent in vitro and CFD analysis was conducted to predict the emitted dose (ED; as a % of loaded dose) and aerosol mass median aerodynamic diameter (MMAD) produced by each device when actuated with 10 ml air bursts. CFD simulations of device operation were used to predict flow field and particle-based dispersion parameters.Results: Comparisons of experimental and CFD results indicated that multiple flow field and particle-based dispersion parameters could be used to predict ED (minimum RMS Error = 4.9%) and MMAD (minimum RMS Error = 0.04 μm) to a high degree of accuracy. Based on experiments, the best overall device produced mean (standard deviation; SD) ED=82.9(4.3)% and mean MMAD (SD)=1.73(0.07)μm, which were in close agreement with the CFD predictions. Conclusions:A unique relationship was identified in the DAC-unit DPI in which reducing turbulence also reduced the MMAD.

Optimizing Aerosolization Using Computational Fluid Dynamics in a Pediatric Air-Jet Dry Powder Inhaler

“…The current study builds upon the initial experimental work with pediatric air-jet DPIs presented by Farkas et al (21), and the devices and results from that study are referred to as Experimental Iteration 1. In the current study, CFD models are developed for the devices in Experimental Iteration 1 and initial CFD dispersion parameters are calculated based on our previous work with low (~10 mL) actuation volumes (8,9). A second round of pediatric airjet devices is then prototyped and tested experimentally, which is referred to as Experimental Iteration 2.…”

“…Design factors that were kept constant included the insertion length of the capillary in the capsule, capsule size, piecing angle, piercing location (along the long axis of the capsule), and a horizontal orientation of the device. Preliminary experimental work considered angling the inlet capillary relative to the outlet capillary, similar to Case 7 in the Longest et al study (9), in an effort to increase secondary flow, but there was little improvement in aerosolization performance. Similarly, preliminary work extended the outlet capillary length in an effort to expose the aerosol to high shear flow for a longer duration, but again there was no improvement in MMAD or ED compared with Experimental Iteration 1.…”

“…The Initial Device Development stage (Figure 1) is largely covered by the work presented in our previous publications on pediatric air-jet DPI development (8,9,21). Here the initial airjet DPI concept was developed with a combination of analytical, experimental, and numerical methods.…”

“…Our group has developed a series of high efficiency air-jet DPIs that are operated with 10 ml of air (via a syringe) (7)(8)(9). These air-jet DPIs use small-gauge hollow capillaries that pierce a powder-containing capsule as part of loading the device, and serve as the air inlet and aerosol outlet.…”

“…The inlet capillary supplies a high-velocity, compressible, turbulent jet that initially fluidizes the powder bed. It is expected that significant turbulence and high shear forces further break up the initially formed aggregates, which reduces the particle size while in the capsule chamber (8,9). Once the size of an aerosolized aggregate is sufficiently reduced, it is able to escape the powder chamber through the outlet capillary and enter the patient interface.…”