An individual who was both an anti-vaxxer and anti-masker claimed that “studies were done that show that surgeons who wore N95 masks for extended periods of time were shown to have decreased oxygen levels and were more prone to mistakes.” His argument was “imagine what that would do to kids who were forced to wear masks all day in school.”

Because everything I had been reading indicated that masks did not decrease oxygen levels, this sounded like important, earth-shattering news. I thought it should be easy to find the studies in question. I looked in all the usual places including PubMed, Google Scholar, and of course, good old Google. My search was fruitless. I didn’t give up. I persevered until I finally located one study that seemed to support the anti-vaxxer’s claims … sort of. But not really.

The Study

The study in question was a “preliminary report” based on pulse oximeter readings on fifty-three surgeons in Turkey and published in the journal Neurocirugía in Asturias, Spain in 2008 and apparently never replicated during the ensuing thirteen years. Neurocirugía is a relatively obscure journal with a low impact factor.

In the Introduction, the authors say “it seems reasonable that some of the exhaled CO2 may also be trapped beneath them, inducing a decrease in blood oxygenation.” It may “seem reasonable;” but this is speculation, not science. It has been tested and is simply not true.

They tested small groups of five to twenty-five subjects as they performed operations of various durations: less than 60 minutes, 60–120 minutes, 120–180 minutes, and 180–240 minutes. They found that as the length of the operation increased, the surgeons’ oxygen levels went down and their pulse rates went up. This might have been alarming; but the researchers had also tested surgeons who were not wearing masks, and guess what? They also had decreased oxygen levels and higher pulse rates!

They commented that the changes “may be due to the facial mask or the operational stress since similar changes were observed in the group performing surgery without a mask.” They didn’t say the surgeons made mistakes; but even if they did, isn’t it likely that mistakes might be due to simple fatigue, stress, or flagging attention during long operations? There is simply no evidence that masks caused any cognitive impairment.

N95 Masks and Rigorous Science

N95 masks, also called respirators, are single use disposable devices. To be effective, they must be properly fitted. They are not designed for children, for whom a proper fit cannot be achieved. Rather than discarding after a single use as intended, some people try to re-use them. “N95 respirators can be safely decontaminated without undermining functional integrity only two or three times, a government study showed.” No method of decontaminating masks has been approved by the CDC.

Numerous scientific studies have measured oxygen levels and found no decrease when wearing an N95 mask or any other mask, with or without valves and with or without exercise. In fact, they found a slight increase in oxygen levels. Nurses who wore an N95 mask for an entire twelve-hour shift had no decrease in oxygen levels but did have elevations in CO2 levels. This was also true for pregnant women during exercise. The rise in CO2 was minimal (3 percent) and stabilized after fifteen minutes. The rise was statistically significant, but was it clinically significant? Did it cause any impairment in performance or cognitive functions? These studies didn’t address that, but a 2020 study showed that masks had no effect on performance during vigorous exercise. And here’s another study that showed no impairment.

According to experts, “There is no solid scientific evidence that wearing masks causes hypoxia or cognitive impairment. Doctors and healthcare workers who work in operating rooms wear them for hours a day and there has been no evidence that these people have had cognitive decline.”

A 2021 study on the effects of wearing masks on oxygen and ventilation at rest and during physical activity found that “The risk of pathologic gas exchange impairment with cloth masks and surgical masks is near-zero in the general adult population.”

The only information discouraging face masks is disinformation provided by unreliable sources from alternative medicine; all the usual suspects: Mercola, Buttar, Tenpenny, as well as many similarly untrustworthy sources.

What about Schoolchildren?

As for the anti-vaxxer’s concern about “what that would do to kids who were forced to wear masks all day in school,” that doesn’t even make any sense. Kids don’t have decreased oxygen levels when wearing any kind of mask, and N95 masks have not been shown more likely to cause hypoxia than other masks. Anyway, kids don’t wear N95 disposable masks because they are not designed for kids and can’t be properly fitted. In all the pictures you have seen of kids wearing masks in school, have you ever seen a single child wearing an N95 mask? Of course not! And because there is no evidence that surgeons were prone to making more mistakes when wearing a mask, there’s no reason to imagine that masks would impair the performance or the learning ability of children.

The Bottom Line

Anti-maskers are indulging in irresponsible fearmongering. The studies they talk about don’t exist. What would mask mandates do to children? It would save some lives.