Masks have no effect on our gas exchange

A scientific experiment shows that wearing a mask has no impact on the exchange of oxygen and carbon dioxide in the body in healthy people or people with respiratory problems.

This was one of the major arguments of anti-mask groups. Wearing it could cause hypoxia (lack of oxygen ) and breathe our own carbon dioxide (CO 2 ). This argument could be brushed aside by our mechanistic knowledge. Indeed, most masks make it possible to stop infectious droplets which have a diameter of between 1 and 10 micrometers . The molecules of oxygen and carbon dioxide measure, respectively, 346 picometers and 330 picometers. Therefore, there was no serious reason to believe that such phenomena were possible. American researchers nevertheless wanted to carry out an experiment on this subject which they published in  Annals of the American Thoracic Society .

No impact of masks on gas exchange 

Thirty people were recruited for the experiment: 15 people from hospital medical staff in good health (average age 31) and 15 veterans suffering from chronic obstructive pulmonary disease ( COPD , average age 71). The experiment was to measure several parameters (heart rate, frequency of breathing, oxygen saturation, end-tidal carbon dioxide, the pressure oxygen and pressure of carbon dioxide only for people with severe lung disease) at different times: 

  • at the start of the experiment, without wearing the mask; 
  • after five minutes of wearing a mask at rest; 
  • after thirty minutes of wearing a mask at rest; 
  • after a walking test for 6 minutes after wearing for 30 minutes at rest (only in people with COPD).

The results show that, in healthy people, only the heart rate is slightly affected, which may explain, according to the authors, by neurological reactions or by exacerbation of anxiety or claustrophobia . In people with COPD, a slight decrease in oxygenation flow was observed after the walk test without any major physiological changes in gas exchange measurements being observed. Before performing this experiment, similar conclusions were drawn in a control group, not finding any change in gas exchange during one hour of moderate activity.

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Wear your mask! 

The scientists’ observations, although limited by sample size, provide fairly clear evidence that surgical masks do not cause problems in gas exchange, unlike FFP2 masks. Indeed, in previous experiments, the latter could cause a slight accumulation of carbon dioxide in the lungs of healthy people. However, this never translated into real physiological damage .

Here is how the study investigators conclude their article: “  It is important to inform the public that the discomfort associated with the use of the mask should not lead to the belief that there are unfounded safety concerns, because this may mitigate the application of a proven practice to improve public health. As growing evidence indicates that asymptomatic individuals may fuel the spread of Covid-19 , the universal use of masks must be vigorously enforced in community settings, especially now that we face a pandemic. with a minimum of therapeutic interventions. We believe our data will help allay fears about the health risks associated with the use of surgical masks and improve public confidence for more widespread acceptance and use. “