This investigation determined cardiorespiratory responses of subjects with normal lung function and exercise tolerance and compared them with subjects with moderate impairment of lung function and exercise tolerance. The respirator was an air-line full-face mask (MSA-Ultravue) "pressure-demand" breathing type equipped with an inspiratory resistance of 85 mmH2O at 85 L/min air flow. This resistance was operable in conjunction with the fixed 25 mmH2O inspiratory and expiratory resistance required to pressurize the face piece. Physiologically and subjectively the response of the normal and moderately impaired subjects to respirator wear during rest, 35%, 50% and 80% of their maximal aerobic capacity (VO2max) were not different. However, the pressure swings inside the face piece exceeded 24 cmH2O and resulted in 50% of the subjects being unable to finish 10 minutes of work at 80% VO2max. The greater the ventilatory demand placed upon the respirator due to increasing workload, the more like a "demand" system pressure-flow response the "pressure-demand" system produced. Hence, the concept of increased protection and reduced inspiratory resistance as a result of pressurizing the facepiece during heavy work is seriously questioned.
This investigation determined the cardiorespiratory responses of subjects with normal lung function and exercise tolerance and compared them with subjects with moderate and severe impairment of lung function and exercise tolerance. Comparisons were made during work while wearing an industrial respirator. The respirator was a full-face mask (MSA-ultravue) "demand" breathing type equipped with an inspiratory resistance of 85 mm H2O at 85 L/min air flow and an expiratory resistance of 25 mm H2O at 85 L/min air flow. Physiologically and subjectively the response of the normal and moderately impaired subjects to respirator wear during rest, 35%, 50% and 63% of their maximal workloads were not different. However, when the moderately impaired worked at 63% of their maximum the workload was equivalent to 50% of maximum of the normal subject. Significant differences in the peak flow/pressure ratio of the severely impaired compared to the normals and moderately impaired were found. By relating work performance to the dyspnea index (VI/MBC) it was suggested that the relationship between maximal lung function and maximal work performance needs to be identified both with and without respirators. This relationship may prove suitable in predicting performance during respirator wear.
Protection Factors provided by 25 NIOSH approved supplied-air respirators were determined while the devices were worn by a panel of test subjects anthropometrically selected to represent adult facial sizes. Polydispersed DOP aerosol was used for respirator fit tests on continuous flow, demand, and pressure-demand respirators. Based on facepiece leakage measurements it appears that demand-type respirators should neither be used nor approved. The highest level of protection was provided by pressure-demand devices.
This report describes the work performed during FY 1977 for the Nuclear Regulatory Commission. The Protection Factors (efficiency) provided by 25 NIOSH approved supplied-air respirators were determined while the devices were worn by a panel of anthropometrically selected test subjects. The major recommendation was that demand-type respirators should neither be used nor approved.
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