Physiologic Effects of Elastomeric Half-Mask Respirator Use with or Without a Surgical Mask in Healthcare Workers

RATIONALE: Elastomeric half-mask respirators (EHMRs) have seen expanded use during the COVID-19 pandemic. Due to concern that persons with asymptomatic COVID-19 infection could potentially transmit infectious respiratory droplets via the exhalation port of an EHMR, some propose placing a surgical mask (SM) over the exhalation port. The physiologic effects of wearing a SM over the exhalation port of an EHMR are unknown. METHODS: We recruited 12 healthy healthcare worker volunteers (92% female, mean age 34.1 years, mean BMI 24.3 kg/m2). Subjects completed a series of simulated healthcare-related activities, including resting, talking, walking and bending, proning and supinating a 172-pound manikin, and performing cardiopulmonary resuscitation (CPR). This 30-minute series was repeated three times, each with a different mask configuration: SM only, EHMR only, or EHMR with SM covering the exhalation port. Each subject's transcutaneous carbon dioxide (tcPCO2), oxygen saturation (SpO2), and heart rate (HR) were measured continuously using a noninvasive transcutaneous sensor (Sentec Inc.). Subjects rated their rate of perceived exertion (RPE) and level of discomfort after each round. Results were analyzed using mixed linear models with a fixed effect for mask type, activity, age, BMI, and gender. A random intercept was included to account for dependency in observations. Testing also included an interaction between mask type and activity. RESULTS: Mean tcPCO2, SpO2, and HR values fell in the normal range for all activities and all mask configurations (Figure). We found statistically but not clinically significant differences in tcPCO2, SpO2, and HR between EHMR with SM and EHMR only. There were decreases in mean tcPCO2 (-0.63, p < 0.001) and SpO2 % (-0.22, p = 0.002), and an increase in HR (+1.51 bpm, p < 0.001) when using EHMR with SM compared to EHMR only. There were similar decreases in mean tcPCO2 (-0.61, p < 0.001) and SpO2 % (-0.27, p < 0.001), and an increase in mean HR (+1.00 bpm, p = 0.018) when comparing EHMR with SM and SM only. Age, BMI, and gender had no significant effect. RPE and discomfort scores were higher with either EHMR configuration compared to SM only. CONCLUSION: Wearing a SM over an EHMR did not produce clinically significant changes in tcPCO2, SpO2, and HR compared to uncovered EHMR during healthcare-related tasks, including patient proning and CPR. Despite higher exertion and discomfort scores with either EHMR configuration, clinically significant changes in tcPCO2, SpO2, and HR were not observed.