Carbon dioxide rebreathing in respiratory protective devices: influence of speech and work rate in full-face masks

Smith, Carmen L; Whitelaw, Jane L; Davies, Brian

doi:10.1080/00140139.2013.777128

Cited by 61 publications

(57 citation statements)

References 6 publications

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“…Although the mechanism by which these acute exercise alterations were afforded differs from conventional altitude training, similar responses have previously been described in environmental hygiene scenarios where external respirators are worn (26). In those situations, the addition of inspiratory and expiratory resistance, as well as dead space, contributes to reductions in R R and a small increase in V T (2,16).…”

Section: Discussionmentioning

confidence: 57%

“Functional” Respiratory Muscle Training During Endurance Exercise Causes Modest Hypoxemia but Overall is Well Tolerated

Granados

Gillum

Castillo

et al. 2016

Journal of Strength and Conditioning Research

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A novel commercial training mask purportedly allows for combined respiratory muscle training and altitude exposure during exercise. We examined the mask's ability to deliver on this claim. Ten men completed three bouts of treadmill exercise at a matched workload (60%VO2peak) in a controlled laboratory environment. During exercise, the mask was worn in 2 manufacturer-defined settings (9,000 ft [9K] and 15,000 ft [15K]) and a Sham configuration (∼3,500 ft). Ventilation (V(E)), tidal volume (V(T)), respiratory rate (R(R)), expired oxygen (F(E)O2) and carbon dioxide (F(E)CO2), peripheral oxygen saturation (S(P)O2), heart rate, and RPE were measured each minute during exercise, and subjects completed the Beck Anxiety Inventory (BAI) immediately after. The mask caused a reduction in V(E) of ∼20 L/min in both the 9K and 15K configurations (p < 0.001). This was due to a reduction in R(R) of ∼10 b·min, but not V(T), which was elevated by ∼250 ml (p < 0.001). F(E)O2 was reduced and F(E)CO2 was elevated above Sham in both 9K and 15K (p < 0.001). VO2 was not different across conditions (p = 0.210), but VCO2 trended lower at 9K (p = 0.093) and was reduced at 15K (p = 0.016). V(E)/VO2 was 18.3% lower than Sham at 9K and 19.2% lower at 15K. V(E)/VCO2 was 16.2% lower than Sham at 9K and 18.8% lower at 15K (all p < 0.001). Heart rate increased with exercise (p < 0.001) but was not different among conditions (p = 0.285). S(P)O2 averaged 94% in Sham, 91% at 9K, and 89% at 15K (p < 0.001). RPE and BAI were also higher in 9K and 15K (p < 0.010), but there was no difference among mask conditions. The training mask caused inadequate hyperventilation that led to arterial hypoxemia and psychological discomfort, but the magnitude of these responses were small and they did not vary across mask configurations.

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Section: Discussionmentioning

confidence: 57%

“Functional” Respiratory Muscle Training During Endurance Exercise Causes Modest Hypoxemia but Overall is Well Tolerated

Granados

Gillum

Castillo

et al. 2016

Journal of Strength and Conditioning Research

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“…In this context, it is therefore perhaps not surprising that FFRs are known to adversely affect the comfort of the wearer in terms of, for example, lowered thermal comfort [ 1 – 3 ] and elevated CO 2 levels [ 4 , 5 ]. The decreased thermal comfort is mainly due to increased humidity and temperature inside the dead space of the FFR from respiration and thermal regulation, which together give rise to a significantly higher apparent temperature than the ambient under normal conditions; apparent temperatures around 53°C have been measured by Roberge et al [ 3 ] for ambient conditions of 22°C and 24% relative humidity.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Carbon Dioxide in Filtering Facepiece Respirators with an Active-Venting System: A Computational Study

Birgersson

Tang²,

Lee³

et al. 2015

PLoS ONE

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During expiration, the carbon dioxide (CO2) levels inside the dead space of a filtering facepiece respirator (FFR) increase significantly above the ambient concentration. To reduce the CO2 concentration inside the dead space, we attach an active lightweight venting system (AVS) comprising a one-way valve, a blower and a battery in a housing to a FFR. The achieved reduction is quantified with a computational-fluid-dynamics model that considers conservation of mass, momentum and the dilute species, CO2, inside the FFR with and without the AVS. The results suggest that the AVS can reduce the CO2 levels inside the dead space at the end of expiration to around 0.4% as compared to a standard FFR, for which the CO2 levels during expiration reach the same concentration as that of the expired alveolar air at around 5%. In particular, during inspiration, the average CO2 volume fraction drops to near-to ambient levels of around 0.08% with the AVS. Overall, the time-averaged CO2 volume fractions inside the dead space for the standard FFR and the one with AVS are around 3% and 0.3% respectively. Further, the ability of the AVS to vent the dead-space air in the form of a jet into the ambient – similar to the jets arising from natural expiration without a FFR – ensures that the expired air is removed and diluted more efficiently than a standard FFR.

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“…Numerous health and safety standards for respiratory protective equipment state the level of CO 2 in the inspired air should not exceed 1%. [15][16][17] Therefore, HCWs considering use of the modified full-face snorkel mask should be aware that this option does not meet minimum safety standards for PPE, and may result in increased inspired CO 2 levels.…”

Section: Discussionmentioning

confidence: 99%

“…The observed rise in the FiCO 2 level for the full-face snorkel mask was substantial, and breached current health and safety regulations for respiratory PPE, which state that inspired CO 2 levels should not rise above 1%. [15][16][17] In terms of demographics, the age, gender, and ethnicity of participants evaluating the respiratory PPE options varied substantially. The age of participants ranged from 24 to 66 years old.…”

Section: Ergonomic Assessments and Qualitative Fit Testing Of Ppe Solmentioning

confidence: 99%

Recommended Personal Protective Equipment for Cochlear Implant and Other Mastoid Surgery During the COVID‐19 Era

et al. 2020

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Objectives/Hypothesis: The overall aim of this study was to evaluate personal protective equipment (PPE) that may facilitate the safe recommencement of cochlear implantation in the COVID-19 era, with the broader goal of minimizing the period of auditory deprivation in prelingually deaf children and reducing the risk of cochlear ossification in individuals following meningitis. Methods: The study design comprised 1) an objective assessment of mastoid drilling-induced droplet spread conducted during simulated cochlear implant (CI) surgery and its mitigation via the use of a protective drape tent and 2) an evaluation of three PPE configurations by otologists while performing mastoid drilling on ex vivo temporal bones. The various PPE solutions were assessed in terms of their impact on communication, vital physiological parameters, visual acuity and fields, and acceptability to surgeons using a systematic risk-based approach. Results: Droplet spread during simulated CI surgery extended over 2 m, a distance greater than previously reported. A drape tent significantly reduced droplet spread. The ensemble of a half-face mask and safety spoggles (foam lined safety goggles) had consistently superior performance across all aspects of clinical usability. All other PPE options were found to substantially restrict the visual field, making them unsafe for microsurgery. Conclusions: The results of this preclinical study indicate that the most viable solution to enable the safe conduct of CI and other mastoid surgery is a combination of a filtering facepiece (FFP3) mask or half-face respirator with safety spoggles as PPE. Prescription spoggles are an option for surgeons who need to wear corrective glasses to operate. A drape tent reduces droplet spread. A multicenter clinical trial to evaluate the effectiveness of PPE should be the next step toward safely performing CI surgery during the COVID-19 era.

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Carbon dioxide rebreathing in respiratory protective devices: influence of speech and work rate in full-face masks

Cited by 61 publications

References 6 publications

“Functional” Respiratory Muscle Training During Endurance Exercise Causes Modest Hypoxemia but Overall is Well Tolerated

“Functional” Respiratory Muscle Training During Endurance Exercise Causes Modest Hypoxemia but Overall is Well Tolerated

Reduction of Carbon Dioxide in Filtering Facepiece Respirators with an Active-Venting System: A Computational Study

Recommended Personal Protective Equipment for Cochlear Implant and Other Mastoid Surgery During the COVID‐19 Era

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