Chest drain aerosol generation in COVID-19 and emission reduction using a simple anti-viral filter
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Abstract
The COVID-19 pandemic has been characterised by significant in-hospital virus transmission and deaths among healthcare workers. Sources of in-hospital transmission are not fully understood, with special precautions currently reserved for procedures previously shown to generate aerosols (particles <5 μm). Pleural procedures are not currently considered AGPs (Aerosol Generating Procedures), reflecting a lack of data in this area.
Methods
An underwater seal chest drain bottle (R54500, Rocket Medical UK) was set up inside a 60-litre plastic box and connected via an airtight conduit to a medical air supply. A multichannel particle counter (TSI Aerotrak 9310 Aerosol Monitor) was placed inside the box, allowing measurement of particle count/cubic foot (pc/ft 3 ) within six channel sizes: 0.3–0.5, 0.5–1, 1–3, 3–5, 5–10 and >10 μm. Stabilised particle counts at 1, 3 and 5 L/min were compared by Wilcoxon signed rank test; p values were Bonferroni-adjusted. Measurements were repeated with a simple anti-viral filter, designed using repurposed materials by the study team, attached to the drain bottle. The pressure within the bottle was measured to assess any effect of the filter on bottle function.
Results
Aerosol emissions increased with increasing air flow, with the largest increase observed in smaller particles (0.3–3 μm). Concentration of the smallest particles (0.3–0.5 μm) increased from background levels by 700, 1400 and 2500 pc/ft 3 at 1, 3 and 5 L/min, respectively. However, dispersion of particles of all sizes was effectively prevented by use of the viral filter at all flow rates. Use of the filter was associated with a maximum pressure rise of 0.3 cm H 2 O after 24 hours of flow at 5 L/min, suggesting minimal impact on drain function.
Conclusion
A bubbling chest drain is a source of aerosolised particles, but emission can be prevented using a simple anti-viral filter. These data should be considered when designing measures to reduce in-hospital spread of SARS-CoV-2.
Article activity feed
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SciScore for 10.1101/2020.07.13.20152264: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. 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:These data were recorded as part of a comprehensive risk assessment process, which demonstrated no significant limitation of air flow through the chest drain circuit with the filter in-situ. Aerosols are typically generated by …
SciScore for 10.1101/2020.07.13.20152264: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. 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:These data were recorded as part of a comprehensive risk assessment process, which demonstrated no significant limitation of air flow through the chest drain circuit with the filter in-situ. Aerosols are typically generated by air moving across the surface of a liquid, with increasing air forces generating smaller particles. [1] This is consistent with the observations reported here in that unfiltered emissions of the smallest particles (0.3-0.5 microns) increased progressively from 1 to 3 to 5 L/minute. Our findings are also concordant with a recent study reported by Akhtar et al, in which a similar anti-viral filter was evaluated and produced a qualitative reduction in droplet emissions. However, droplet size, and therefore aerosolization potential were not examined. [8] These data support risk mitigation in patients with suspected or proven COVID-19, as recommended by the British Thoracic Society (BTS) [6] and the American Association for the Surgery of Trauma (AAST). [7] However, the absolute risk involved remains uncertain. Pleural effusion and pneumothorax appear uncommon complications of COVID-19 (occurring in ∼5% and ∼1% of cases, respectively [6][8]) and an aerosol-generating chest drain can clearly only be an infection risk if SARS-CoV-2 is a) present in any effusion drained (which may be of minimal volume in patients with pneumothorax and major air-leaks) and b) remains viable long enough to be aerosolised. Lescure [3] and Mei [4] have recently reported cases of SA...
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.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
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