A Surgeon's Perspective: Mask wearing and Hypercapnia

Join Dr. Van Dyken as she discusses whether wearing a mask contributes to high carbon dioxide (CO2) levels, also known as hypercapnia.Links to papers referenced:https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2044.2006.04767.xhttp://www.rcjournal.com/contents/05.10/05.10.0569.pdfLet’s talk about a new perspective in regards to mask wearing and COVID-19. Just recently I’ve been seeing a lot of social media posts regarding mask wearing and high carbon dioxide levels medically known as hypercapnia. It definitely got me thinking, I mean conceptually it kind of makes sense, and it made me wonder whether there is any evidence for this. Let’s break it down and look at the facts and evidence.High CO2 levels in the blood can be harmful and it can cause a myriad of symptoms depending on the level of carbon dioxide in your blood. It can cause things like an altered mental state, irregular heartbeat, loss of consciousness, altered decision making, breathing difficulties and, worst of all, when levels are really high - it can be fatal. So is there any evidence behind wearing a mask and hypercapnia? Here is a study that begins with an anecdotal report - of an ICU doctor who experienced what was believed to be hypercapnia after spending 30 minutes in a PFR 95 (N95) respirator. The same article references how they looked at four anesthetists that also were the same type of mask – they measured expired carbon dioxide and saw a slight increase. No one reported any symptoms of hypercapnia. interesting article, interesting anecdote, but the study was small – it only looked at four subjects and most importantly – it did not actually study the type of mask that most people use when going out and about - this is a cloth mask, or even a surgical mask. This is the mask they studied - as opposed to these masks- which most people are wearing. The authors conclude the study stating: “clearly, our findings are of uncertain practical significance and further trials would be required.”Masks have been around for a while. They’ve been used regularly in the healthcare setting for over 100 years. If hypercapnia were a serious problem with mask wearing I would think we would have been tipped off to this problem by now, don’t you? So let's talk about my experience. I am a surgeon. There are times when I operate and I wear a mask continuously for up to nine hours. ALL of the other individuals working in the operating room with me like the anesthesiologist and the nurse and scrub tech wear masks as well, NONE OF US get dangerously high carbon dioxide levels in our blood from doing so. As a matter of fact - we don’t show any of the aforementioned symptoms. This is for a long surgery, not a 20 minute trip to the grocery store or any other short time we have to wear a mask while in public.Why is this? Why do we not get hypercapnia?It comes down to particle size. Masks are meant to reduce the spread of droplets that are formed by talking and sneezing - these droplets could contain harmful particles. Let's take a look at the SARS-CoV-2 virus particle, since that is the reason we are all currently advised to wear masks. Particle size of this virus is about .125 microns. When this virus is in droplet form, most masks will stop it from spreading outside of the mask. Compare that to the size of a carbon dioxide molecule - .000232 microns. This molecule is about 1000 times smaller than the virus - and so are oxygen and nitrogen molecules. These small gaseous molecules can easily sneak through a mask, even through an N95 respirator. Cloth masks and surgical masks have been shown to allow these molecules easy passage in and out of the mask. So - if carbon dioxide can easily pass through the mask - there is no way it can build up and cause hypercapnia. It’s just not going to happen.So how could it possibly happen? It could happen if you were wearing something that had no ventilation properties whatsoever, like a plastic bag over your head. This bag would not allow carbon dioxide to escape, and as you exhale the concentration of carbon dioxide goes up and up causing hypercapnia. You would also get hypoxia, or low oxygen levels because the fresh air outside the plastic bag can’t get in. But this is NOT how regular masks work. When you wear a mask, air moves with each breath, as it is designed to. If this didn’t happen we would see people having symptoms of hypercapnia. Healthcare workers routinely wear surgical masks for hours on end - there is no hypercapnia happening there that we know of! So next time you hear somebody mentioning hypercapnia - ask for evidence. Please don’t believe this misinformation! Wearing a mask is an important part of slowing the spread of COVID-19 - along with other measures like physical distancing and handwashing. If you find any more evidence on mask wearing and hypercapnia- let me know. I would love to see tons of rigorous studies on this - hopefully researchers get this done soon!