Abstract
Previous researches have pointed that the primary leakage of respiratory masks originated from the misfit in the nasal and menton regions. Recent studies on the design of mask using 3D anthropometry data have achieved promising result. A newly proposed two-stage sizing method is first to segment the whole user population into “large” and “small” size groups on face size against individual’s objective allowance, then 3D face seal line for every subject within each size group are extracted, and all the 3D face seal lines are registered on both ends (on nasal and menton landmarks) and superimposed, viewing from the side all the lines exhibit a series of line (like magnetic lines) arisen from both ends, the variation of these curve line are then further segmented into 2 depth groups against depth allowance of the elasticity of the mask skirt. However, this method does not particularly address the leakage problem arises in the bony regions for their non-pliant sharp curve and bony tissue. As a consequence, this study is undertaken to investigate the variance of 3D curve lines of the interface seal in the bony regions of nasal and menton for the refinement of the shape and deformation range of the mask skirt.Based on the result of this newly method, the e-constructed mask is fitted on Solidworks software for each subject within each group to check the goodness of fit. Some mis-fits were observed: the mask skirt in nasal region was too narrow for the widest subject (46.6mm) and too shallow for the highest subject (21.7mm); in menton region, it was too wide for the narrowest subject (76mm). Thus, the subject with maximum and minimum of nasal width, nasal height, and menton width was identified as reference to refine the shape and measurements of the mask skirt. The maximum width and height of nasal was used to determine the shape of hard shell, and the minimum width and height of nasal was used to determine the shape of the mask skirt; similarly, the maximum width of menton was used to determine the shape of hard shell, and the minimum width of menton was used to determine the shape of the mask skirt. After refinement, the fit was significantly improved.