Wearing face mask unlikely to cause overexposure to CO2, even in those with lung disease

In a new study, wearing a surgical face mask did not cause gas exchange abnormalities in healthy adults or in adults with lung function impairment, researchers reported in the Annals of the American Thoracic Society.

“It is important to inform the public that the discomfort associated with mask use should not lead to unsubstantiated safety concerns as this may attenuate the application of a practice proven to improve public health,” Rajesh Samannan, MD, with Jackson Memorial Hospital, Miami, and colleagues wrote. “As growing evidence indicates that asymptomatic individuals can fuel the spread of COVID-19, universal mask use needs to be vigorously enforced in community settings, particularly now that we are facing a pandemic with minimal proven therapeutic interventions.”

Researchers assessed changes in end-tidal CO₂ and oxygen saturation before and after wearing a surgical mask. The study included 15 physicians without lung conditions (mean age, 31 years; 60% men) and 15 male veterans with severe chronic obstructive pulmonary disease (mean age, 71.6 years; mean FEV₁ 44). The patients with COPD were enrolled during a scheduled 6-minute walk test, during which all patients are currently required to wear a surgical mask. The researchers obtained baseline room air measures without a mask using a Life Sense monitor, followed by continuous monitoring with a surgical mask.

The researchers observed no major changes of clinical significance in tidal CO₂ and oxygen saturation of clinical significance at 5 and 30 minutes nor at any time point in either group at rest. Mean end-tidal CO₂ was 36.2 mm Hg at baseline without a mask, with a change of 1.06 mm Hg at 5 minutes while wearing a surgical mask at rest and 0.75 mm Hg at 30 minutes while wearing a surgical mask at rest. Mean oxygen saturation was 97.5% at baseline, with a change of –0.28% at 5 minutes while wearing a surgical mask at rest and 0.10% at 30 minutes while wearing a surgical mask at rest, according to the results.

Patients with COPD did not exhibit major physiologic changes in gas exchange measurements following the 6-minute walk test with a surgical mask and had decreased oxygenation during the walk test, which was expected, according to the researchers. In this group, mean end-tidal CO₂ was 36.1 mm Hg at baseline, with a change of –1.67 mm Hg at 5 minutes while wearing a surgical mask at rest, –1.63 mm Hg at 30 minutes while wearing a surgical mask at rest and before the walk test and –0.14 mm Hg at 30 minutes while wearing a surgical mask and after the walk test. Mean oxygen saturation was 91.3% at baseline, with a change of 0.35% at 5 minutes while wearing a surgical mask at rest, 0.87% at 30 minutes while wearing a surgical mask at rest and before the walk test and –2.28% at 30 minutes while wearing a surgical mask and after the walk test, according to the results.

“Dyspnea, the feeling of shortness of breath, felt with masks by some is not synonymous of alterations in gas exchange. It likely occurs from restriction of air flow with the mask in particular when higher ventilation is needed,” Michael Campos, MD, of the Miami Veterans Administration Medical Center and the division of pulmonary, allergy, critical care and sleep medicine at University of Miami, said in a related press release. “We show that the effects are minimal at most, even in people with very severe lung impairment.”

“The public should not believe that masks kill,” Campos said.

Reference:

Press Release.