Near-field airborne particle concentrations in young children undergoing high-flow nasal cannula therapy: a pilot study

Gall, Elliott T.; Laguerre, Aurélie; Noelck, Michelle; Meurs, Annalise Van; Austin, Jared P.; Foster, B.A.

doi:10.1016/j.jhin.2021.04.002

Cited by 5 publications

(12 citation statements)

References 21 publications

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“…Appendix A of the Supplemental document describes two case studies that present results of near-and far-eld magni ers for a recent controlled study on individuals that were diagnosed with COVID-19 (Supplemental table 2), 3 as well as a study of patients undergoing high-ow nasal cannula therapy. 20 Speci cally, as shown in Supplemental tables 3, the concentration of CO 2 and the particles of 1 µm -2.5 µm in the controlled study on participants who were diagnosed with COVID-19 3 were ~8 % and ~12 % higher in the near eld (4 ft from the participants), compared to the far eld (11 ft from the participants), respectively 3 . The present study provides con rmatory results in that the concentration of targeted VOCs in the near-eld (2.5 ft) was ~10% higher than the far-eld (7.5ft) during steady-state periods, thusproviding greater con dence for the concept of breath tracers as a proxy for virus laden bioaerosols.…”

Section: Discussionmentioning

confidence: 90%

A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields

Parhizkar¹,

Fretz²,

Laguerre³

et al. 2022

Preprint

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Several studies suggest that far-field transmission (> 6 ft) explains the significant number of COVID-19 superspreading outbreaks. Therefore, quantitative evaluation of near- and far-field exposure to emissions from a source is key to better understanding human-to-human airborne infectious disease transmission and associated risks. In this study, we used an environmentally-controlled chamber to measure volatile organic compounds (VOCs) released from a healthy participant who consumed breath mints, which contained unique tracer compounds. Tracer measurements were made at 2.5 ft, 5 ft, 7.5 ft from the participant, as well as in the exhaust plenum of the chamber. We observed that 2.5 ft trials had substantially (~36-44%) higher concentrations than other distances during the first 20 minutes of experiments, highlighting the importance of the near-field relative to the far-field before virus-laden respiratory aerosol plumes are continuously mixed into the far-field. However, for the conditions studied, the concentrations of human-sourced tracers after 20 minutes and approaching the end of the 60-minute trials at 2.5 ft, 5 ft, and 7.5 ft were only ~18%, ~11%, and ~7.5% higher than volume-averaged concentrations, respectively. Our findings highlight the importance of far-field transmission of airborne pathogens including SARS-CoV-2, which need to be considered in public health decision making.

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Section: Discussionmentioning

confidence: 90%

A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields

Parhizkar¹,

Fretz²,

Laguerre³

et al. 2022

Preprint

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“…In one study [ 20 ] the team measured near-field and far-field CO 2 concentrations to estimate magnifiers in patient rooms within a healthcare environment having 8–11 ACH. The authors reported background (far-field) CO 2 concentrations of 580 ppm (mean across 7 patients) and reported near-field mean CO 2 concentrations of 605 ppm, thus only 25 ppm higher than background, which equates to a near-field magnifier of 4.3% [ 20 ]. We note that the uncertainty in CO 2 measurements for most systems reported in the literature is ±50 ppm.…”

Section: Discussionmentioning

confidence: 99%

“…The implications of magnifiers in a real-world case study The purpose of this section is to compare the results of near -field and far-field magnifiers for the present study and two recent relevant studies [3,20]. In one study [20] the team measured near-field and far-field CO 2 concentrations to estimate magnifiers in patient rooms within a healthcare environment having 8-11 ACH.…”

Section: Discussionmentioning

confidence: 99%

“…The authors found that the near-field was associated with a higher number of virus RNA copies, and statistically higher carbon dioxide (CO 2 ), and particle counts of 0.3 µm -2.5 µm than in the far-field [3]. Differences between nearfield and far-field were also examined through the comparison of CO 2 and particles with patients receiving high-flow nasal cannula therapy (HFNC), where the CO 2 concentration was statistically higher at a distance 0.5 m (~1.6 ft) from the source emitter compared to background levels [20].…”

Section: Introductionmentioning

confidence: 99%

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A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields; implications for the spread of respiratory viruses

Parhizkar

Fretz

Laguerre

et al. 2022

J Expo Sci Environ Epidemiol

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Background Several studies suggest that far-field transmission (>6 ft) explains a significant number of COVID-19 superspreading outbreaks. Objective Therefore, quantifying the ratio of near- and far-field exposure to emissions from a source is key to better understanding human-to-human airborne infectious disease transmission and associated risks. Methods In this study, we used an environmentally-controlled chamber to measure volatile organic compounds (VOCs) released from a healthy participant who consumed breath mints, which contained unique tracer compounds. Tracer measurements were made at 0.76 m (2.5 ft), 1.52 m (5 ft), 2.28 m (7.5 ft) from the participant, as well as in the exhaust plenum of the chamber. Results We observed that 0.76 m (2.5 ft) trials had ~36–44% higher concentrations than other distances during the first 20 minutes of experiments, highlighting the importance of the near-field exposure relative to the far-field before virus-laden respiratory aerosol plumes are continuously mixed into the far-field. However, for the conditions studied, the concentrations of human-sourced tracers after 20 minutes and approaching the end of the 60-minute trials at 0.76 m, 1.52 m, and 2.28 m were only ~18%, ~11%, and ~7.5% higher than volume-averaged concentrations, respectively. Significance This study suggests that for rooms with similar airflow parameters disease transmission risk is dominated by near-field exposures for shorter event durations (e.g., initial 20–25-minutes of event) whereas far-field exposures are critical throughout the entire event and are increasingly more important for longer event durations. Impact statement We offer a novel methodology for studying the fate and transport of airborne bioaerosols in indoor spaces using VOCs as unique proxies for bioaerosols. We provide evidence that real-time measurement of VOCs can be applied in settings with human subjects to estimate the concentration of bioaerosol at different distances from the emitter. We also improve upon the conventional assumption that a well-mixed room exhibits instantaneous and perfect mixing by addressing spatial distances and mixing over time. We quantitatively assessed the exposure levels to breath tracers at alternate distances and provided more insights into the changes on “near-field to far-field” ratios over time. This method can be used in future to estimate the benefits of alternate environmental conditions and occupant behaviors.

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“…3 Differences between near-eld and far-eld were also examined through CO 2 and particles with patients receiving high-ow nasal cannula therapy (HFNC), where the CO 2 concentration was statistically higher at a distance 0.5 m (~1.6 ft) from the source emitter compared to background levels. 20 The goal of the present study is to better characterize the impact of distance from source on distribution of exhaled bioaerosols in an indoor environment. A novel trace gas approach is proposed where a participant consumed breath mints and released known compounds in exhaled breath.…”

Section: Introductionmentioning

confidence: 99%

A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields

Parhizkar

Fretz

Laguerre

et al. 2022

Preprint

View full text Add to dashboard Cite

Several studies suggest that far-field transmission (> 6 ft) explains the significant number of COVID-19 superspreading outbreaks. Therefore, quantitative evaluation of near- and far-field exposure to emissions from a source is key to better understanding human-to-human airborne infectious disease transmission and associated risks. In this study, we used an environmentally-controlled chamber to measure volatile organic compounds (VOCs) released from a healthy participant who consumed breath mints, which contained unique tracer compounds. Tracer measurements were made at 2.5 ft, 5 ft, 7.5 ft from the participant, as well as in the exhaust plenum of the chamber. We observed that 2.5 ft trials had substantially (~ 36–44%) higher concentrations than other distances during the first 20 minutes of experiments, highlighting the importance of the near-field relative to the far-field before virus-laden respiratory aerosol plumes are continuously mixed into the far-field. However, for the conditions studied, the concentrations of human-sourced tracers after 20 minutes and approaching the end of the 60-minute trials at 2.5 ft, 5 ft, and 7.5 ft were only ~ 18%, ~ 11%, and ~ 7.5% higher than volume-averaged concentrations, respectively. Our findings highlight the importance of far-field transmission of airborne pathogens including SARS-CoV-2, which need to be considered in public health decision making.

show abstract

Near-field airborne particle concentrations in young children undergoing high-flow nasal cannula therapy: a pilot study

Cited by 5 publications

References 21 publications

A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields

A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields

A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields; implications for the spread of respiratory viruses

A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields

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