Physiological impact of different types of mask at rest

INTRODUCTION: Due to the mandatory use of a mask in the context of the Covid-19 pandemic, we set out to evaluate the physiological impact of hypoxia and hypercapnia generated by different masks at rest. METHODS: Thirty-two competitive adolescent athletes (40% female) were evaluated. Room air and intra-mask measurements were taken at rest while sitting in a chair. A spirometric study was performed and the intra-mask concentration of O2 and CO2 was evaluated, comparing 3 situations: a) Home (H): mask that the subject was wearing from home. b) Surgical (S): surgical mask. c) KN95 mask (KN95). RESULTS: The ambient air in the laboratory was: O2: 20.9% and CO2: 544 ± 67 ppm (0.05%); Intra-mask O2: H: 17.8 ± 0.72 %; S: 17.08 ± 0.62 %; KN95: 16.8 ± 0.56 %; (H vs S: ns; H vs NK95: p <0.001; S vs KN95: p <0.002). Intra-mask CO2: H: 1.81 ± 0.52 %; S 1.92 ± 0.35 %; KN95: 2.07 ± 0.36%; (H vs S: ns; H vs NK95: p <0.001; S vs KN95: p <0.012). CO2 levels with KN95 were lower in men 1.97 ± 0.37 % vs 2.2 ± 0.29 % than in women (p<0.04), with a significant correlation between gender and weight (r: 0.98, p: 0.01) and height (r: 0.78, p: 0.01). CONCLUSIONS: The KN95 mask presented a lower concentration of O2, and a higher concentration of CO2 compared to the baseline situation with the surgical masks and those home-made. There is a difference in CO2 between the sexes when the KN95 mask was used, in relation to weight and height.