Effect of transient inhalation on powder evacuation and dispersion in a typical dual air inlet dry powder inhaler

An optically accessible research dry powder inhaler (DPI) was used to investigate the impact of initial acceleration during inhalation on the powder evacuation and drug dispersion processes. The inhaler featured a swirling chamber connected with two inlets, closely resembling commercial devices such as the Aerolizer (R) and Osmohaler (R). The dimensions of the inhaler were kept similar to the commercial devices, mimicking their flow situations. High-speed microscopic imaging and an in-house developed image processing technique were used to extract relevant statistics. The current literature on DPI flow dynamics provides valuable insights into the correlation between inspiratory flow rate, peak inspiratory pressure, and inhaler performance. However, it lacks data correlating powder evacuation characteristics and deagglomeration mechanisms for transient inhalation conditions inside the DPIs. This paper is an attempt to fill this gap by investigating the evacuation pattern and deagglomeration mechanism for three different initial accelerations qualitatively representing asthma severity and steady-state inhalation conditions representing laminar, transitional, and turbulent channel flow, using both pure drug and carrier particles. The study's key findings revealed that powder evacuation progressed in two stages. The first stage was slow, with a slope ranging from 0.25 to 0.27. Also, the evacuation rate was independent of the initial inhalation acceleration. The second stage was rapid, with a slope ranging from 0.87 to 1.23, which led to faster and complete powder evacuation. The slow stage consumed approximately -60 % of the total evacuation time to evacuate only -20% of the loaded drug, while the rapid stage evacuated -80% of the powder in the remaining time. The data collected from these experiments advances the understanding of the DPI flow dynamics and provides highquality data for validating computational models used in the analysis of such inhaler systems.