Inhaled CO 2 concentration while wearing face masks: a pilot study using capnography
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Abstract
None of the available evaluations of the inhaled air carbon dioxide (CO 2 ) concentration, while wearing face masks, used professional, real-time capnography with water-removal tubing. We measured the end-tidal CO 2 using professional side-stream capnography, with water-removing tubing (Rad-97™ capnograph), at rest, (1) without masks, (2) wearing a surgical mask, and (3) wearing a FFP2 respirator, in 102 healthy volunteers aged 10-90 years, from the general population of Ferrara province, Italy. The inhaled air CO 2 concentration was then computed as: ((mask volume × end-tidal CO 2 ) + ((tidal volume - mask volume) × ambient air CO 2 )) / tidal volume).
The mean CO 2 concentration was 4965±1047 ppm with surgical masks, and 9396±2254 ppm with FFP2 respirators. The proportion of the sample showing a CO 2 concentration higher than the 5000 ppm acceptable exposure threshold recommended for workers was 40.2% while wearing surgical masks, 99.0% while wearing FFP2 respirators. The mean blood oxygen saturation remained >96%, and the mean end-tidal CO 2 <33 mmHg. Adjusting for age, gender, BMI, and smoking, the inhaled air CO 2 concentration significantly increased with increasing respiratory rate (with a mean of 10,143±2782 ppm among the participants taking 18 or more breaths per minute, while wearing FFP2 respirators), and was higher among the minors, who showed a mean CO 2 concentration of 12,847±2898 ppm, while wearing FFP2 respirators. If these results will be confirmed, the current guidelines on mask-wearing could be updated to integrate recommendations for slow breathing and a more targeted use when contagion risk is low.
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SciScore for 10.1101/2022.05.10.22274813: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Strengths and weaknesses of the study: The chosen capnography device had water-removal tubing, and real-time monitoring, ensuring reliable and reproducible CO2 measurements.(26) Indeed, relative humidity ranges 42-91% in exhaled air,(11) potentially altering CO2 assessments,(12) which might explain the differences with the measurements …
SciScore for 10.1101/2022.05.10.22274813: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Strengths and weaknesses of the study: The chosen capnography device had water-removal tubing, and real-time monitoring, ensuring reliable and reproducible CO2 measurements.(26) Indeed, relative humidity ranges 42-91% in exhaled air,(11) potentially altering CO2 assessments,(12) which might explain the differences with the measurements of previous studies.(9, 10) Additionally, we examined the largest sample, so far, of healthy individuals of various ages, comparing both surgical masks and FFP2 respirators.(9, 10) This study has also limitations that must be considered. First, although the sample size is the largest as yet, it is still relatively scarce, especially for the minors. Secondly, the volume of the dead space within the mask could not be assessed for each participant, and therefore we could not closely inspect the possible influence of face shape and individual added dead space on the inhaled air CO2. Thirdly, the instrument’s precision of 1.5 mmHg (1974 ppm) widens the uncertainty around the measurements. Importantly, however, when 1974 ppm are subtracted to the mean inhaled air CO2, the CO2 in surgical masks decreases to about 3000 ppm, while it still exceeds the 5000 ppm threshold with FFP2 respirators.(18) Lastly, the experimental conditions, with participants at complete rest and in a constantly ventilated room, were far from those experienced by workers and students during a typical day, normally spent in rooms shared with other people or doing some degree of p...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- No funding statement was detected.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
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