Air Flow Entrainment of Lactose Powder: Simulation and Experiment

Abstract

Lactose powder is frequently used as an excipient in drug formulations for use in dry powder inhalers (DPIs). As a patient inhales through a DPI the lactose powder is entrained into the airflow, thus enabling delivery of the drug dose to the patient’s lungs. Computational fluid dynamics (CFD) can potentially aid the designers of DPIs if the entrainment process can be accurately simulated. In this study we compare CFD simulations and experimental observations of entrainment of lactose powder using an example 2D DPI geometry and typical inhalation airflow profiles. 2D transient CFD simulations were carried out using an Eulerian-Eulerian solver to model the progression of entrainment subject to two example patient inhalation maneuvers: one high and one low flow rate. Experiments used the same 2D geometry laser cut from a 3 mm thick opaque acrylic sheet sandwiched between transparent sheets. A powder dose was pre-loaded before assembly of the geometry. Two different lactose powders were used with particle sizes of 59 and 119 µm. Air flow was provided by a computer controlled pump (a breath simulator). The geometry was back lit and the progression of entrainment was filmed at 1000 fps. Comparison of the CFD simulations and experimental results showed good agreement for the two powders tested.