PURPOSE: COVID-19 pandemic led to wide-spread use of face-masks, respirators and other personal protective equipment (PPE) by healthcare workers . Various symptoms attributed to the use of PPE are believed to be, at least in part, due to elevated carbon-dioxide (CO2) levels . We evaluated concentrations of CO2 under various PPE .
METHODS: In a prospective observational study on healthy volunteers, CO2 levels were measured during regular breathing while donning 1) no mask , 2) JustAir® powered air purifying respirator (PAPR), 3) KN95 respirator, and 4) valved-respirator . Serial CO2 measurements were taken with a nasal canula at a frequency of 1-Hz for 15-min for each PPE configuration to evaluate whether National Institute for Occupational Safety and Health (NIOSH) limits were breached .
RESULTS: The study included 11 healthy volunteers, median age 32 years (range 16-54) and 6 (55 %) men . Percent mean (SD) changes in CO2 values for no mask, JustAir® PAPR, KN95 respirator and valve respirator were 0.26 (0.12), 0.59 (0.097), 2.6 (0.14) and 2.4 (0.59), respectively . Use of face masks (KN95 and valved-respirator) resulted in significant increases in CO2 concentrations, which exceeded the 8-h NIOSH exposure threshold limit value-weighted average (TLV-TWA). However, the increases in CO2 concentrations did not breach short-term (15-min) limits . Importantly, these levels were considerably lower than the long-term (8-h) NIOSH limits during donning JustAir® PAPR . There was a statistically significant difference between all pairs (p <0.0001, except KN95 and valved-respirator (p = 0.25). However, whether increase in CO2 levels are clinically significant remains debatable .
CONCLUSION: Although, significant increase in CO2 concentrations are noted with routinely used face-masks, the levels still remain within the NIOSH limits for short-term use . Therefore, there should not be a concern in their regular day-to-day use for healthcare providers . The clinical implications of elevated CO2 levels with long-term use of face masks needs further studies . Use of PAPR prevents relative hypercapnoea . However, whether PAPR should be advocated for healthcare workers requiring PPE for extended hours needs to evaluated in further studies.