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. Optimal 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 speeding VHC emptying and improving overall aerosol delivery efficiency and dose. Masks may have different DSV and thus different performance. OBJECTIVES To compare both physical dead space and functional dead space of different face masks under various applied pressures. METHODS The DSV of three commonly used face masks 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 masks have different DSV characteristics. This variability should be taken into account when comparing the clinical efficacy of various VHCs.