Does wearing a facemask decrease arterial blood oxygenation and impair exercise tolerance?

Abstract

Introduction: Concerns have been raised that COVID-19 face coverings compromise lung function and pulmonary gas exchange to the extent that they produce arterial hypoxemia and hypercapnia during high intensity exercise resulting in exercise intolerance in recreational exercisers. This study therefore aimed to investigate the effects of a surgical, flannel or vertical-fold N95 masks on cardiorespiratory responses to incremental exercise.

Methods: This investigation studied 11 adult males and females at rest and while performing progressive cycle exercise to exhaustion. We tested the hypotheses that wearing a surgical (S), flannel (F) or horizontal-fold N95 mask compared to no mask (control) would not promote arterial deoxygenation or exercise intolerance nor alter primary cardiovascular variables during submaximal or maximal exercise.

Results: Despite the masks significantly increasing end-expired peri-oral %CO₂ and reducing %O_2, each ∼0.8-2% during exercise (P < 0.05), our results supported the hypotheses. Specifically, none of these masks reduced sub-maximal or maximal exercise arterial O₂ saturation (P = 0.744), but ratings of dyspnea were significantly increased (P = 0.007). Moreover, maximal exercise capacity was not compromised nor were there any significant alterations of primary cardiovascular responses (mean arterial pressure, stroke volume, cardiac output) found during sub-maximal exercise.

Conclusion: Whereas these results are for young healthy recreational male and female exercisers and cannot be applied directly to elite athletes, older or patient populations, they do support that arterial hypoxemia and exercise intolerance are not the obligatory consequences of COVID-19-indicated mask-wearing at least for cycling exercise.

Keywords: COVID-19 facemask; Cardiovascular responses; Cycle exercise; Dyspnea; Exercise-induced arterial hypoxemia; Exhaustion; Maximal; N95; Rating of perceived exertion; Submaximal; Surgical facemask.

Fig. 1

Illustration of experimental set-up for evaluation of the resistance to flow across each mask (A). The pressure difference across each mask for multiple flow rates demonstrates that a substantial difference exists for all masked conditions compared to control, with the greatest difference for the N95 mask (B). Calculation of resistance at 48 L min⁻¹ revealed a higher resistance to air flow for all masks (C).

Fig. 2

Average (±SD) values during the incremental exercise test up to 120 W for arterial oxygen saturation (SpO₂), Borg dyspnea scores, heart rate (HR), mean arterial pressure (MAP), stroke volume (SV), and cardiac output (CO). Dyspnea rating was significantly increased with each facemask, but, with the exception of a small increase in HR for the surgical and N95 masks, no other cardiovascular variables were impacted significantly by any mask across multiple submaximal exercise work rates. * P < 0.05 for N95 vs. no mask condition. + P < 0.05 for all masked conditions vs. no mask condition.

Fig. 3

Average (±SD) values for peak power, arterial oxygen saturation (SpO₂) and dyspnea scores at peak exercise for each facemask condition. Note the lack of difference for peak power and SpO₂ among conditions, but the presence of increased dyspnea. * P < 0.05 vs. no mask condition.