Background: For good lung deposition, when using a pressurized metered dose inhaler (pMDI) with valved holding chamber (VHC) and facemask, it is essential that the facemask provides a good seal, and comfortable fit. Actual parameters for in vitro bench testing of newly developed facemasks, to predict clinical use, are not well known. For this reason, a custom instrumented OptiChamber Diamond VHC with medium LiteTouch facemask, known as the Facemask Datalogger, was developed to measure application force and air flow through the VHC and facemask. The aim was to test usability of the Facemask Datalogger and to collect in vivo data using the Facemask Datalogger. Outcomes were application force (measured as weight), and time needed to empty the VHC (TVHC).
Methods: Thirty asthmatic children aged 1-5 years, already using a pMDI/VHC with facemask. Using the Facemask Datalogger, one parent applied the facemask on the child simulating normal inhalation, and force and flow were recorded. This was repeated 3 times.
Results: Mean application force: 411 g (SD ±161). Inter-subject variability of mean force: 39% (CV) and mean intra-subject variability of mean force 23% (CV). Mean (TVHC): 6.9 s (SD ±5.5), and TVHC was significantly negatively correlated with age (r= -0.6; p<0.001)
Conclusion: The Facemask Datalogger is a useful tool to measure in vivo application force on a facemask and air flow through a VHC. Mean force measured was lower than that referenced in previous in vitro studies. These results will assist development and testing of new facemasks in vitro.