The use of filtering facepiece respirators (FFR) has increased enormously in both public and occupational sectors for respiratory protection from infectious airborne particles. The N95 class of FFR, which filters out at least 95% of airborne particles >0.3 um, is the most common type of FFR; however, there has been a lack of scientific information on physiological and thermal burdens of wearing N95 FFR. PURPOSE: To investigate physiological and thermoregulatory responses to wearing N95 FFRs while performing low-moderate intensity exercise. METHODS: Twenty healthy subjects (13 men, 7 women), who passed a physical examination and a respirator quantitative fit test, performed three trials of treadmill exercise (5.6 km/h, 0% grade, 60min duration) in a thermoneutral environment (21.4+0.7oC, 23.5=7.9%) while wearing two popular styles (cup-shaped and flat fold) of N95 FFR or not wearing FFR for control (CON). Study variables included core body temperature (Tco), skin temperature at the cheek (Tcheek) and abdomen (Tabdomen), heart rate (HR), respiratory rate (RR), transcutaneous carbon dioxide (tcPCO2), and oxygen saturation (SpO2). Deadspace microclimate temperature and humidity were also measured in FFR trials. Data were analyzed by two-way (Trials xTime) repeated measures ANOVA. RESULTS: Tco, Tcheek, and Tabdomen rose significantly by time in all trials (p<0.001) and the final deadspace microclimate temperature and humidity reached up to 33oC and 90%, respectively. However, there was no statistical difference in these temperature variables between CON and the FFR trials. HR and RR increased significantly by time in all trials (p<0.001), but at a greater rate in the FFR trials than in CON (HR; P<0.001, RR; P<0.01). There was no statistical difference in SpO2 levels between CON and FFR trials, however, tcPCO2 levels were significantly higher in the FFR trials than in CON (p<0.001). CONCLUSION: Wearing N95 FFR while performing low-moderate work for 60 min in a thermoneutral environment did not impose a significant thermal burden on the wearer. However, significantly elevated HR and RR in the FFR trials indicated that wearing N95 FFR may add additional metabolic demands. Also, breathing through N95 FFR did not interfere with SpO2, but caused some mild degree of CO2 retention (tcPCO2 .>_45 mmHg).
Respirators; Respiratory-equipment; Respiratory-protection; Respiratory-protective-equipment; Filters; Particulate-dust; Particulates; Airborne-dusts; Airborne-particles; Physiological-function; Physiological-effects; Physiological-factors; Thermal-effects; Physical-exercise; Temperature-effects; Temperature-measurement; Statistical-analysis