Assessment of the physiological loads and subjective discomforts while wearing non-powered tight-fitting air-purifying respirator with canister and N95 facemask

• Main Authors: Wei-Chieh Liu, 劉惟潔
• Other Authors: 許文信
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/75096202429364326170

碩士 === 中國醫藥大學 === 職業安全衛生學系碩士班 === 95 === This study aim to evaluate the most frequently used non-powered tight-fitting air-purifying respirators with canister and N95 facemasks. The N95 facemask which the facepiece itself is the purifying element is also used by medical personnel. Research results have indicated the respirators are available and in use in only 20-30% of the work phases evaluated as needing them. Failure to use a respirator is influenced by the physiological burden caused by such as additional respiratory resistance and dead space, by psychological factors such as subjective discomforts, and by thermo stress caused by the environment and respirator itself. There were lots of researches addressing the physiological effects whilst wearing respirators with canister. Only little research focused on N95 facemask which is associated with smaller breathing resistance when compared with respirator with canister. However, the N95 facemask is still need to be assessed because it may become wet and the breathing resistance may increase after prolonged use. The subjective discomfort associated with respirator wearing has not been studied systematically, but it is widely agreed that user’s discomfort represents a crucial issue to interfere with the use of respirators. Two experiments were conducted in the present study. The study intended to assess the physiological loads and subjective discomforts and their effects on the wearing behaviour for non-powered tight-fitting air-purifying respirator with canister and N95 facemask. The first experiment aimed to evaluate and compare the physiological loads and subjective discomforts between N95 facemask and a full-facepiece respirator. The second experiment explored furthermore about the effects of wearing N95 facemask with or without expiratory valve and the effects of speaking or not while wearing the two types of N95 facemasks. 18 medical university students (9 males and 9 females) with mean age about 24 year olds completely participated in the two experiments. The evaluated independent variables in the first experiment included gender (GR), types of respirator (RT), including ball type N95 facemasks with/without valve (BWV, BNV), full-facepiece respirator with chemical canister or N95 filter(FWC, FWN) and work loads (WL, 45W and 85W). The explored independent variables in the second experiments included gender, types of respirator (ship-type N95 face mask with/without valve, SNV and SWV), work load (45W and 85W) and task (TK, speaking or not). All independent variables in the two experiments except gender were designed as within-subject variables. The evaluated dependent variables for the two experiments were identical which included working and work pulse, peak inspiratory and expiratory resistance (PIP, PEP), respiratory frequency (RF), temperature inside respirator (TIR), minute ventilation (VE), volume of oxygen consumption (VO2) and subjective rating of perceived exertion (RPE) for five categories. Results of the first experiments showed that wearing respirators significantly increased the working pulse and work pulse. Both of the effects of RT on working and work pulse were not significant. The PIP and PEP measured for the four experiment respirators were consistent with the measured inspiratory and respiratory resistance for each respirator. The PIP value was the highest for FWC and was the lowest for BNV. The PEP value was the highest for FWC and was the lowest for BWV. The TIR for BNV was the highest followed by BWV and were significantly higher than FWC and FWN. The VE and VO2 for FWC and FWN were significantly higher the BWV and BNV. The effects of WL on the five RPEs were all significant. As for the effects of RT on RPE, only significantly higher RPE for the temperature inside the respirator was reported. The results of the second experiment showed that the effects of RT on working and work pulse were not significant. The PIP, PEP and TIR for SNV were significantly higher than those for SWV. Therefore the SWV was recommended. The effects of TK on working pulse, work pulse, PIP, PEP and RF were significant. The working and work pulse were 3-4 beats/min higher for the task with speaking than task without speaking. The effects of WL on RPE were significant. The RPE score for SNV was significantly higher than that of SWV which could be attributed to the RPE for the temperature inside the respirator. The RPEs for the task with speaking were all significantly higher than task without speaking. The results of RPE were consistent with the measured physiological work load indicators.