CO2 Levels Behind and in Front of Different Protective Mask Types

Objectives

Many individuals have difficulty adapting to face mask use and report symptoms while using masks. Our primary objective was to determine whether continuous mask-wearing causes elevated levels of carbon dioxide (CO₂) behind the facemasks.

Methods

CO₂ concentrations were measured behind 3 different types of face masks and were compared to CO₂ concentrations at the mask front in 261 subjects who continuously wore masks for at least 5 minutes. These CO₂ concentrations were also measured in several randomly selected subjects after a 5-minute walk.

Results

There were significantly higher CO₂ concentrations behind the mask (3176 ppm) compared to the front (843 ppm) with an average of 49 minutes of continuous mask use. Of all the subjects, 76.6% had a behind-the-mask CO₂ concentration of more than 2000 ppm (the threshold for clinical symptoms), and 12.2% had a CO₂ concentration of at least 5000 ppm (occupational health exposure limit). The CO₂ level behind the N-95 masks was highest (especially after exertion) and was lowest behind cloth masks. The combination of warm ambient temperature, an N-95 mask, exercise, and young age appeared to induce exceedingly high CO₂ levels that should be avoided.

Discussion

Although masks might be necessary for healthcare workers or to lessen the spread of airborne disease, we found that elevated CO₂ concentrations were present while wearing them. Elevated CO₂ concentrations have historically caused symptoms of CO₂ toxicity. Periodic mask breaks in designated areas may be needed to avoid adverse effects.

Conclusion

The use of masks increased the CO₂ concentration in the air behind them to levels historically associated with toxicity.

SARS-CoV-2 Antibody Positivity and Prevalence in an Outpatient Medical Setting in Las Vegas, NV

Background

SARS-CoV-2 antibody testing shows the prevalence of COVID-19 disease in different communities and has epidemiological significance.

Methods

SARS-CoV-2 IgM and IgG were tested in 319 patients, staff and visitors of a primary care clinic in Las Vegas, NV on a continuous as-requested basis.

Results

Prevalence of SARS-CoV-2 antibodies was 3.76% in a primary care office in Las Vegas, NV. Positivity of IgM was 0.31% and IgG 3.44%. The most common symptoms reported amongst those who tested positive were cough, shortness of breath and loss of smell and taste. The most common comorbidities included hypertension, chronic lung disease, seasonal allergies, and type 2 diabetes mellitus, in that order.

Conclusion

Prevalence was 2.3% in Washoe County, NV in June 2020 and 3.76% in Clark County, NV in April-June 2020. This has important implications for heavily populated urban areas.

The iliac bone or osteocutaneous transplant pedicled to the deep circumflex iliac artery. I. Anatomical and technical considerations

The technique of microsurgical vessel anastomosis has brought about many new ideas in reconstructive surgery. Many bone sites have been examined for their suitability as donor areas. For reconstructive purposes in the maxillo-facial region, the iliac bone has proven to be the best because of its shape and bulk. A large part of this bone is nourished by the deep circumflex iliac artery (DCIA). Branches of this vessel surround the iliac crest, perforate the flat abdominal muscles, and supply blood to the overlying skin. The anatomical properties of this region present the possibility of raising a large osteomyocutaneous flap.