Effect of Face #Masks on Gas Exchange in Healthy Persons and Patients with #COPD

..In order to demonstrate the changes in end-tidal CO2 (ETCO2) and oxygen saturation (SpO2) before and after wearing a surgical mask, we used a convenience sample of 15 housestaff
physicians without lung conditions (aged 31.1  1.9 years, 60% male) and 15 veterans with severe COPD (aged 71.6  8.7 years, FEV1 44.0  22.2%, 100% male).

The patients needed to
have a post-bronchodilator FEV1 <50% and FEV1/FVC <0.7 and were enrolled from the
pulmonary function laboratory during a scheduled 6-minute walk test ordered to assess the
need for supplemental oxygen. In our institution, the 6-minute walk tests are done with arterial blood analysis before and immediately after the walk to assess the need for long-term oxygen.

Due to the COVID-19 pandemic, the 6-minute walk tests are done with subjects using a surgical
mask. As this was a clinical observation study, exemption from the local IRB was obtained.
Baseline measures on room air without a mask were performed non-invasively using a Life
Sense monitor (model Ls1-9R, Nonin Medical, Plymouth, MN), followed by continuous
monitoring using a surgical mask.

At 5 and 30 minutes, no major changes in ETCO2 or SpO2 of clinical significance were
noted at any time point in either group at rest (Table 1). With the 6-minute walk, subjects with
severe COPD decreased oxygenation as expected (with 2 qualifying for supplemental oxygen).
However, as a group, subjects with COPD did not exhibit major physiologic changes in gas
exchange measurements after the 6-minute walk test using a surgical mask, particularly in CO2
retention.

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