AN EXPERIMENTAL SETUP FOR API ASSESSMENT OF A VALVED HOLDING CHAMBER DEVICE

摘要

Typically for young children and elders, the asthma treatment procedure using pMDI devices bring some usage coordination difficulties. Therefore, and accordingly to several asthma treatment guidelines, the prescription of a VHC, as an add-on device for the pMDI, is advisable. These devices consist of an expansion chamber where the air slows down, as well as, the pMDI spray plume. Allowing the patient to breathe whenever he wants, independently from the moment of the pMDI actuation, also reduces the "cold-freon" effect and allows a more effective evaporation of the propellant. The effectiveness evaluation of VHC and pMDI devices is made through the quantification of drug delivered to the patient lungs. A simple collection filter is not enough for an accurate assessment of the device. Since the size of the particles delivered matter the most, the use of an impaction apparatus is essential. Accordingly to the Canadian normative for VHC assessment (CAN/CSA/Z264.1-02:2008), the experimental testing shall be done by using a breath simulator instead of a constant flow pump. The evolution of these tests shall move towards more realistic testing conditions. This work reports the project and construction an experimental setup for a correct assessment of the VHC devices effectiveness. The experimental setup is based in the work of Foss & Keppel (1999) and the contribution of Finlay (1998) and Miller (2002). The project and optimization of the major components, such as, breath cycle simulator by means of a cam-follower mechanism, a mixing cone and the vacuum pump used, are herein described and discussed.