The Design of Respiratory Mask Using 3D Cranial Facial Database

• Main Author: 廖秀珍
• Other Authors: 游志雲
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/65739017337631050310

碩士 === 國立清華大學 === 工業工程與工程管理學系 === 93 === This study proposes a design method for half-face respiratory masks based on an existing 3-D head database, aiming at the air-tightness of faceseal. The database contains a total of 270 subjects, 135 males and 135 females, which were drawn from Taiwanese worker population based on the body size distribution of two previous anthropometrical surveys. The distribution was classified into 5 staure heights and 3 body weights. The 3-D surface of the head was measured using a six-head Gemini scanner. The design method consists of two phases: extraction of 3-D faceseal contour and contruction of mask body. The extraction of 3-D faceseal contour proceeded in 3 steps: sizing on face-length, drawing of 2-D contour, and extraction of 3-D faceseal contour. Since the face-lengths range between 82.6 mm and 115.8 mm, with a range difference of 33.2 mm, so they were classified into two size groups: “size S” is from 82.6 mm to 98.2 mm and “size L” is from 98.2 mm to 115.8 mm. Within each size group, the one whose face-length is the most close to the mean was chosen as the representatives samples to determine the representative 2-D contour. The representative 2-D contour is a closed contour which is drawn on the front view of the face of the representative sample, its top begins with mid-nasal point, then it curves outward (to the right and left) and downward and traverses the infraorbital regions, and then to the outer-skirt of bunasolabial sulcus of the buccol regions, and finally along the chin and closes at mentum. Then, this 2-D contour was projected onto each subject to obtain a 3-D faceseal contour. All the 3-D faceseal contours within each size group were registered and superimposed on the menton and mid-nasal. In side view, all of these superimposed faceseal contours exhibits in different depths. The dispersion in depth is a measure of the degree of face difference, and is used for further sizing consideration. Based on past experiences, a difference of 10 mm difference in the bonny nasal and mentum area, and 15 mm difference in the cheek fleshy area are considered as the cutoff criteria for size grouping. Based on these criteria, both size A and size B were required to further classified into two groups, namely “SS”, “SD”, and “LS”, “LD”, in respected to the shallower faces and the deeper faces. Within each size group, the deepest one was chosen as the final representative faceseal contour. The construction of mask body is based on the faceseal and the mid-saggittal contour of the typical sample. The central ridge of the mask was determined based on the mid-saggittal contour of the face. It is a simple curved line elevates above the mid-saggittal contoure with an elevations of 10 mm, 20 mm and 10 mm each at mid-nasal, nasal tip and menton. Next, a horizontal reference contour of the mask was drawn, which passes the 20 mm elevation point at nasal tip and with two end points terminate on the faceseal contour. Then in a similar manner, a series of horizontal contours were drawn at 10 mm interval. All horizontal contours were further interpolated to form a continuous 3-D surface. This surface is the 3-D shape of the mask body. The space between the mask body and the face is the dead space. The dead space volume each for SS, SD, LS, and LD size was 213.3 cm3、235.8 cm3、256.2 cm3 and 285.1 cm3respectively, which is smaller than most existing masks (with a mean of 294.3 cm3 and S.D of 28.5 cm3).