Carbon dioxide re-breathing with close fitting face respirator masks

Refocusing on work-based hazards for the anaesthesiologist in a post-pandemic era

The coronavirus pandemic has raised public awareness of one of the many hazards that healthcare workers face daily: exposure to harmful pathogens. The anaesthesia workplace encompasses the operating room, interventional radiology suite, and other sites that contain many other potential occupational and environmental hazards. This review article highlights the work-based hazards that anaesthesiologists and other clinicians may encounter in the anaesthesia workplace: ergonomic design, physical, chemical, fire, biological, or psychological hazards. As the anaesthesia work environment enters a post-COVID-19 pandemic phase, anaesthesiologists will do well to review and consider these hazards. The current review includes proposed solutions to some hazards and identifies opportunities for future research.

Capillary carbon dioxide tension increases in hospital staff wearing filtering facepiece masks: a prospective crossover study

Background

The COVID-19 pandemic has changed worldwide hygiene practices. In particular, the use of filtering face piece (FFP) masks markedly increased. Concerns have been raised regarding possible negative respiratory effects of wearing FFP masks. The aim of this study was to investigate gas exchange and subjective breathing effort in hospital personnel wearing FFP2 or FFP3 masks.

Methods

In this prospective, single-centre, crossover study, 200 hospital workers were assigned to alternately wear FFP2 or FFP3 masks for 1 h during routine activities. Capillary blood gas analysis was performed to evaluate gas exchange while wearing the FFP masks. The primary end-point was the change in capillary partial pressure of carbon dioxide (P_cCO2). In addition, capillary partial pressure of oxygen (P_cO2), respiratory rate and subjective breathing effort were assessed at the end of each hour. Changes between time points and study groups were estimated using univariate and multivariate models.

Results

P_cCO2 increased from 36.8±3.5 to 37.2±3.3 mmHg (p=0.047) and 37.4±3.2 mmHg (p=0.003) in individuals wearing FFP2 or FFP3 masks, respectively. Age (p=0.021) and male sex (p<0.001) were significantly associated with increased P_cCO2. Similarly, the P_cO2 increased from 70.7±8.4 to 73.4±8.8 mmHg (p<0.001) and 72.8±8.5 mmHg (p=0.004) in individuals wearing FFP2 or FFP3 masks, respectively. Respiratory rate and subjective breathing effort increased significantly while wearing FFP2 and FFP3 masks (p<0.001 for all analyses). The order of wearing FFP2 or FFP3 masks did not significantly affect the results.

Conclusions

An hour of wearing FFP2 or FFP3 masks increased P_cCO2 values, respiratory rate and subjective breathing effort in healthcare personnel performing routine activities.

The Cardiopulmonary Effects of Medical Masks and Filtering Facepiece Respirators on Healthy Health Care Workers in the Emergency Department: A Prospective Cohort Study

Background

International COVID-19 guidelines recommend that health care workers (HCWs) wear filtering facepiece (FFP) respirators to reduce exposure risk. However, there are concerns about FFP respirators causing hypercapnia via rebreathing carbon dioxide (CO₂). Most previous studies measured the physiological effects of FFP respirators on treadmills or while resting, and such measurements may not reflect the physiological changes of HCWs working in the emergency department (ED).

Objective

Our aim was to evaluate the physiological and clinical impacts of FFP type II (FFP2) respirators on HCWs during 2 h of their day shift in the ED.

Methods

We included emergency HCWs in this prospective cohort study. We measured end-tidal CO₂ (ETCO₂), mean arterial pressure (MAP), respiratory rate (RR), and heart rate values and dyspnea scores of subjects at two time points. The first measurements were carried out with medical masks while resting. Subjects then began their day shift in the ED with medical mask plus FFP2 respirator. We called subjects after 2 h for the second measurement.

Results

The median age of 153 healthy volunteers was 24.0 years (interquartile range 24.0–25.0 years). Subjects’ MAP, RR, and ETCO₂ values and dyspnea scores were significantly higher after 2 h. Median ETCO₂ values increased from 36.4 to 38.8 mm Hg. None of the subjects had hypercapnia symptoms, hypoxia, or other adverse effects.

Conclusion

We did not observe any clinical reflection of these changes in physiological values. Thus, we evaluated these changes to be clinically insignificant. We found that it is safe for healthy HCWs to wear medical masks plus FFP2 respirators during a 2-h working shift in the ED.

Inhaled CO2 Concentration While Wearing Face Masks: A Pilot Study Using Capnography

BACKGROUND

Face masks are recommended based on the assumption that they protect against SARS-CoV-2 transmission, however studies on their potential side effects are still lacking. We aimed to evaluate the inhaled air carbon dioxide (CO₂) concentration, when wearing masks.

METHODS

We measured end-tidal CO₂ using professional side-stream capnography, with water-removing tubing, (1) without masks, (2) wearing a surgical mask, and (3) wearing a FFP2 respirator (for 5 minutes each while seated after 10 minutes of rest), in 146 healthy volunteers aged 10 to 90 years, from the general population of Ferrara, Italy. The inhaled air CO₂ concentration was computed as: ([mask volume × end-tidal CO₂] + [tidal volume - mask volume] × ambient air CO₂)/tidal volume.

RESULTS

With surgical masks, the mean CO₂ concentration was 7091 ± 2491 ppm in children, 4835 ± 869 in adults, and 4379 ± 978 in the elderly. With FFP2 respirators, this concentration was 13 665 ± 3655 in children, 8502 ± 1859 in adults, and 9027 ± 1882 in the elderly. The proportion showing a CO₂ concentration higher than the 5000 ppm (8-hour average) acceptable threshold for workers was 41.1% with surgical masks, and 99.3% with FFP2 respirators. Adjusting for age, gender, BMI, and smoking, the inhaled air CO₂ concentration significantly increased with increasing respiratory rate (mean 10 837 ±3712 ppm among participants ⩾18 breaths/minute, with FFP2 respirators), and among the minors.

CONCLUSION

If these results are confirmed, the current guidelines on mask-wearing should be reevaluated.

Inhaled CO2 Concentration While Wearing Face Masks: A Pilot Study Using Capnography

BACKGROUND

Face masks are recommended based on the assumption that they protect against SARS-CoV-2 transmission, however studies on their potential side effects are still lacking. We aimed to evaluate the inhaled air carbon dioxide (CO₂) concentration, when wearing masks.

METHODS

We measured end-tidal CO₂ using professional side-stream capnography, with water-removing tubing, (1) without masks, (2) wearing a surgical mask, and (3) wearing a FFP2 respirator (for 5 minutes each while seated after 10 minutes of rest), in 146 healthy volunteers aged 10 to 90 years, from the general population of Ferrara, Italy. The inhaled air CO₂ concentration was computed as: ([mask volume × end-tidal CO₂] + [tidal volume - mask volume] × ambient air CO₂)/tidal volume.

RESULTS

With surgical masks, the mean CO₂ concentration was 7091 ± 2491 ppm in children, 4835 ± 869 in adults, and 4379 ± 978 in the elderly. With FFP2 respirators, this concentration was 13 665 ± 3655 in children, 8502 ± 1859 in adults, and 9027 ± 1882 in the elderly. The proportion showing a CO₂ concentration higher than the 5000 ppm (8-hour average) acceptable threshold for workers was 41.1% with surgical masks, and 99.3% with FFP2 respirators. Adjusting for age, gender, BMI, and smoking, the inhaled air CO₂ concentration significantly increased with increasing respiratory rate (mean 10 837 ±3712 ppm among participants ⩾18 breaths/minute, with FFP2 respirators), and among the minors.

CONCLUSION

If these results are confirmed, the current guidelines on mask-wearing should be reevaluated.

Comparison of Effects of N95 Respirators and Surgical Masks to Physiological and Psychological Health among Healthcare Workers: A Randomized Controlled Trial

Since the onset of the coronavirus disease 2019 pandemic, wearing facemasks has become more important for healthcare workers. This study aimed to investigate and compare the influence of wearing N95 respirators and surgical masks for 8 h on physiological and psychological health. Sixty-eight healthcare workers were randomly assigned to the N95 respirator or surgical mask groups. Physiological parameters of participants were measured by Tensor Tip MTX at baseline and at the 2nd, 4th, 6th and 8th h of wearing the facemasks. The symptoms after wearing facemasks were also determined via the questionnaire. There were no significant changes in physiological parameters at most time checkpoints in both groups. Significant differences were observed in terms of heart rate at the 8th h, time trends (adjusted difference of least squares means were −8.53 and −2.01), and interaction of time and mask type between the two groups (p-value for interaction was 0.0146). The values of these physiological parameters were within normal ranges. The N95 respirator group had significantly higher incidences of shortness of breath, headache, dizziness, difficulty talking and fatigue that spontaneously resolved. In conclusion, healthcare workers who wore either N95 respirators or surgical masks during an 8 h shift had no obvious harmful effects on physiological and psychological health. Additionally, the N95 respirator group did not show a higher risk than the surgical mask group.

Protective Face Masks: Effect on the Oxygenation and Heart Rate Status of Oral Surgeons during Surgery

Background: Safety in medical work requires eye protection, such as glasses, and protective facial masks (PFM) during clinical practice to prevent viral respiratory infections. The use of facial masks and other full personal protective equipment increases air flow resistance, facial skin temperature and physical discomfort. The aim of the present study was to measure surgeons’ oxygenation status and discomfort before and after their daily routine activities of oral interventions. Methods: 10 male voluntary dentists, specializing in oral surgery, and 10 male voluntary doctors in dentistry, participating in master’s courses in oral surgery in the Department of Oral Surgery of the University of Chieti, with mean age 29 ± 6 (27–35), were enrolled. This study was undertaken to investigate the effects of wearing a PFM on oxygenation status while the oral surgeons were actively working. Disposable sterile one-way surgical paper masks (Surgical Face Mask, Euronda, Italy) and FFP2 (Surgical Face Mask, Euronda, Italy) were used and the mask position covering the nose did not vary during the procedures. The FFP2 was covered by a surgical mask during surgical treatment. A pulse oximeter was used to measure the blood oximetry saturation during the study. Results: In all 20 surgeons wearing FFP2 covered by surgical masks, a reduction in arterial O₂ saturation from around 97.5% before surgery to 94% after surgery was recorded with increase of heart rates. A shortness of breath and light-headedness/headaches were also noted. Conclusions: In conclusion, wearing an FFP2 covered by a surgical mask induces a reduction in circulating O₂ concentrations without clinical relevance, while an increase of heart frequency and a sensation of shortness of breath, light-headedness/headaches were recorded.

Significant physiological impact of wearing PPE inside operation theatre: A challenging scenario in this COVID-19 pandemic

Owing to COVID-19 pandemic, wearing personal protective equipment (PPE) and N95 mask inside an operation theatre has become a common practice. Subjective symptoms of suffocation, headache, dizziness, and lack of concentration while on PPE may at times become significant enough requiring oxygen therapy, removal of mask, or even doffing of PPE, which may increase the risk of being infected and at the same time compromising patient care. The reason behind such subjective symptoms may be multifactorial. We report here a 52-years-old anesthetist with a high body mass index, wearing PPE for a prolonged duration inside an operation theatre during a high-risk surgery encountered a similar episode. Being the lone anesthetist, he decided to oxygenate himself in an innovative way, thus, avoiding doffing and any undesirable event. With pandemic expanding rapidly such scenarios may be encountered often, identifying factors predicting such events and finding methods of oxygenation while wearing PPE may be extremely beneficial.

Quality Assurance During a Global Pandemic: An Evaluation of Improvised Filter Materials for Healthcare Workers

OBJECTIVE

The proliferation of improvised masks during the COVID-19 pandemic has raised questions regarding filter effectiveness and safety. We sought to compare the effectiveness of commonly used improvised filter materials against N95 industry standards.

METHODS

Six different filter materials commonly used in the community were tested using both single- and multi-layer configurations with the TSI 8130 automated filter tester in accordance with National Institute for Occupational Safety and Health (NIOSH) standards for N95 respirators.

RESULTS

Only three of the tested filter material configurations met N95 parameters with regard to filtration efficiency and pressure drop across the filter material-the: True-high-efficiency particulate air (HEPA) filter, four-layer MERV 13 and 14 HVAC filters.

CONCLUSIONS

Many proposed filter materials for improvised masks do not meet current industry standards and may pose safety and efficacy concerns. Care should be taken when selecting materials for this critical respirator component, particularly for health care workers or others at high risk for pathogen exposure.

Respirators used by healthcare workers due to the COVID-19 outbreak increase end-tidal carbon dioxide and fractional inspired carbon dioxide pressure

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Due to COVID-19, compliance of manufactured respirators with standards seems to be placed in the second plan.

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Personal protective equipments (PPE), such as respirators, causes carbon dioxide re-breathing in healthcare workers.

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Even when resting, both expiratory and inspiratory carbon dioxide levels increase significantly with the use of PPE.

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It should be kept in mind that healthcare workers may experience symptoms related to hypercapnia during their use of PPE.