Dead space variability of face masks for valved holding chambers

Background: Valved holding chambers with masks are commonly used to deliver inhaled medications to young children with asthma. Optical mask properties such as their dead space volume have received little attention. The smaller the mask the more likely it is that a greater proportion of the dose in the VHC will be inhaled with each breath, thus speecing VHC emptying and improving overall aerosol delivery efficiency and dose. Mask may have different DSV and thus different performance. Objectives: To compare both physical dead space and functional dead space of different face mask under various applied pressures. Methods: The DSV of three commonly used face mask of VHCs was measured by water displacement both under various pressures (to simulate real-life application, dynamic DSV) and under no pressure (static DSV). Results: There was a great variability of both static and dynamic dead space among various face mask for VHCs, which is probably related to their flexibility. Conclusions: different mask have different DSV characteristics. This variability should be taken into account when comparing the clinical efficacy of various VHCs.