Influence of the valve on the performance of two cylindrical valved holding chambers

Abstract

The use of valved holding chambers (VHCs) is recommended when pressurized metered dose inhalers (pMDI) are prescribed. These medical devices decrease actuation-inhalation coordination difficulties, improve drug delivery and reduce oropharyngeal deposition. In this work, an in vitro and in silico analysis of two commercial VHCs is performed. Both devices are antistatic and are similar in length, volume, shape, but have different valve design (valve seat and flaps). Experimental results, using a Next Generation Impactor, showed that the VHCs differ in their performance, so they are not interchangeable. However, when flaps are not present in commercial VHCs and its 3D prototypes (designed with the same body volume and wall material), the differences in emitted fraction are not significant. In addition, studies performed with computational fluid dynamics showed that the highest particle deposition occurs by impact on the valve. Thus, while multiple factors of VHCs influence the delivered dose, in this work it has been shown that the main one to be considered is the valve design.