Fact or Fiction? Masking and CO2 Dangers

[J.Adderton]

As the COVID-19 pandemic unfolds, health experts continue to urge the public to wear face masks for protection. Sound advice, right? Well.. if you spend any time on social media it’s likely you’ve read warnings about the dangers of wearing a mask for long periods of time. Specifically, the risk of carbon dioxide (CO2) becoming trapped under your mask, causing unsafe levels to build up in the body (hypercapnia). So, let’s take a closer look to see if wearing a mask can lead to someone passing out or worse.

A Possible Catalyst

One April incident added fuel to the “masking causing carbon dioxide poisoning” theory. On April 25, 2020, a New Jersey woman crashed her car into a power pole and was taken to a nearby hospital. The local police department posted to facebook that the woman had been wearing an N95 mask for several hours and passed out. The department believed wearing the N95 mask contributed to the crash by causing a buildup of carbon dioxide and resulting in the driver fainting.

The facebook post was shared thousands of times and received hundreds of comments. The story was also reported on major news outlets.

The Basics

Let’s first review the characteristics of protective masks as we look for the truth. There are two main types of masks used in healthcare, N95 respirators and surgical masks.

Surgical

These masks are fluid resistant, fit loosely and protect you from large droplets, splashes or sprays of body or hazardous fluids. They also protect others from your own respiratory and body secretions. However, there are limits to protection surgical masks provide, including:

• Does not provide reliable protection from small airborne particles
• Are not considered respiratory protection
• Leakage occurs around the edge of the mask when you inhale
• Designed for single use

N95 Respirators

The N95 respirator is tight-fitting and requires a fit test to make you have a good seal around the mask. It protects you against small particle aerosols and large droplets. In fact, it filters out at least 95% of small and large airborne particles. If properly fitted, minimal leakage occurs around the edges when you inhale. N95 masks also have limitations, including:

• Ideally, N95 masks should be discarded after each patient encounter
• Is ineffective if a good seal is not maintained
• Breathing can become difficult

The Verdict

A CDC representative told Reuters that CO2 will build up in face masks over time, however, the level of CO2 trapped is tolerable for most of us. Protective masks are designed to trap droplets, which are much larger than CO2 particles. Therefore, CO2 will escape through or around the edges of surgical, cloth and even N95 masks. If CO2 levels do rise high enough to cause symptoms, we would most likely remove the mask.

Healthcare workers, who wear masks for extended periods of time, could potentially experience symptoms of elevated CO2 levels (I.e. headaches and dizziness).

Caveat: Preexisting Conditions

People with respiratory conditions (such as COPD) that cause hypercapnia may experience breathing difficulties. Therefore, the CDC does not recommend face masks for anyone having breathing difficulties or other conditions that will increase the risk of hypercapnia.

Have you experienced any other “myths” or “truths” related to masking during the pandemic?

References

Driver in crash may have passed out from wearing N95 mask too long: Police

Killer COVID-19 Masks? The Truth About Trapped Carbon Dioxide

[Queen Tiye, RN]

On 7/29/2020 at 2:01 PM, NurseBlaq said:

Anxiety, undiagnosed COPD, asthma exacerbation, bronchitis, etc. There are many reasons but simply wearing a mask isn't it.

I do have bronchitis. Also I realize it become bad after wearing the same mask for 4 or 5 days. I work at a new place and we get to switch our masks daily. Reusing masks to frequently made it harder for me to breathe.

[42pines]

A bit of fact and a bit of fiction.

Depending upon the type of mask you have greater resistance to inhalation/exhalation.  There is also a certain amount of “dead space,” in which air breathed out will get “trapped.”

I like the article “Respiratory consequences of N95-type Mask usage in pregnant healthcare workers—a controlled clinical study.”

(https://dx.doi.org/10.1186%2Fs13756-015-0086-z)

The mask used appears to have a larger tidal volume potential than most masks, including N95 respirators, indicating to me a likely “worst case scenario.”

Wearing an N95 increased the “work” of breathing.  There is an increase of CO2 in the “left-over” air in the dead-space of the mask after each exhalation, but no significant change in the overall incoming (inspiration) of either O2 or CO2.

During exercise maternal heart rate increased “from 89 ± 1.8 to 107 ± 1.9 beats/min.”  From this we can see that, at least for pregnant women, when exercising, they experience a greater workload is indicated in the increased heart rate.  Interestingly the subjects did not reach a statistical subjective increase that would indicate “I’m having to work harder to breathe.”
“There were no differences in finger-tip capillary oxygen saturation levels with the mask and without the mask.”

Conclusions: “While there is a substantial negative change in TV, VE and the VO2 and VCO2 exchanged, there was no impact of breathing through N95 mask materials, to finger-tip oxygen saturation, maternal or fetal heart rate and no drive to increase BF in pregnancy compared to breathing ambient air at the level of exercise in our study. This study shows important descriptive findings of changes to respiratory physiology with mask use, which do not appear to have sufficient significant clinical impact based on the parameters monitored, that had been deliberately kept within the normal ranges to ensure safety of the subjects.”

My take is with an N95 you will work harder to breath but your O2 sat will remain unchanged in healthy, fit subjects.  The authors suggest caution for third-trimester pregnant women working with N95 masks due to the increased work effort.  I would extend that to those who might experience any sort of respiratory issues, not because of reduced oxygen saturation levels, nor due to increased CO2 but simply because if a worker has to repeatedly lift 25lb boxes all day, and has no difficulty doing so, then adding 5lbs to the load is unlikely to produce anything more than increased breathing rate and increased caloric consumption, in short work that’s a bit harder.  If that worker struggles or comes close to struggling to lift that same 25-pound load repeatedly each day, then it would not be wise to subject them to an increased 5-lb load.

So, do masks cause some danger by CO2?  This study says no, even though this study shows that wearing an N95 does make one work harder.

As for asbestos, the “clearance,” generally is to utilize a leaf-blower inside the building for some minutes thus raising the worst-case scenario of left-over asbestos, while the air is being sampled.  That sample is analyzed with TEM or visible light microscopy, actually counting fibers per liter of air in this worst-case scenario.  Clearance is not obtained until the fiber load is lower than ambient (outdoor) air, thus it was not necessary to wear any respirator after abatement.