Evaluation of high flow local extraction for controlling aerosol plumes in operating theaters

  1. Chenlin Sun
  2. Logan Marriott
  3. Matthew Harper
  4. Tongming Zhou

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Abstract

SARS-CoV-2 can be transmitted through contact with fomite, respiratory droplets, and aerosolized viruses. Recent evidence suggests that aerosol transmission represents a significant route of infection. In relation to healthcare workers (HCWs), much attention has been focused on personal protective equipment, yet this is the lowest level of the Centers for Disease Control and Prevention hierarchy of controls. Although engineering controls are prominent in the hierarchy, little attention has been given to developing effective interventions. This study aims to evaluate the performance of a simple extraction device in a clinical setting. This was accomplished by using a high flow local extraction (HFLE) that was connected to the existing ventilation system of the hospital on one end and to an intake nozzle near the patient's airway on the other end. Propylene glycol was aerosolized through a physiological test apparatus to simulate the breath of a patient. The field of interest was illuminated using a laser sheet in two planes from the model, namely, the sagittal plane and the transverse plane, and the movement of the simulated aerosol was recorded using a video camera to assess the dispersion of the aerosol qualitatively. In the meantime, the concentration of the aerosol particles was measured using a particle meter to evaluate the effectiveness of the extraction quantitatively. It was found that the HFLE device could effectively reduce the dispersion of the exhaled aerosols to undetectable levels when it was positioned within 250 mm from the mouth. This result has significance in the safety of HCWs involved in the management of patients with infectious diseases and may also have potential applications in other clinical areas with high airflow in the ventilation systems.

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  1. Version published to 10.1063/5.0096549
  2. ScreenIT

    SciScore for 10.1101/2021.05.16.21257155: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot 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:
    Common weaknesses include inadequate replication of physiological breathing/coughing and the substitution of nebulised liquid droplets for aerosols, and measurement in a single location often upstream of the plume. The importance of further investigations of aerosol behaviours in hospitals cannot be overstated. SARS-CoV-2 has been detected well beyond the distance of droplet spread throughout the hospital, including areas without direct clinical exposure. (35,36) Poor understanding and implementation of building ventilation systems can potentially exacerbate spread. There are clear guidelines outlining the key safety principles of building ventilation for aerosol precautions (37–39). The CDC & WHO recognise that the first step for environmental risk mitigation in tuberculosis patients is local exhaust ventilation, and to avoid airflow designs that cause “short-circuiting” (Appendix 1, Supplementary Figure 3). There are devices (see appendix 3) purporting to scavenge particles at much lower flow rates than HFLE, but as yet they remain unvalidated and provide no efficacy data to support their routine use at this time. The only previous assessment of high flow extraction in the medical literature demonstrated an effective reduction in simulated aerosol levels (13). This, inline with the CDC/NIOSH recommendations has been largely overlooked in major guidelines on the management of airways in patients with COVID-19 (14,40). Indeed, medicine is starkly at odds with other industries...

    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: Please consider improving the rainbow (“jet”) colormap(s) used on page 65. At least one figure is not accessible to readers with colorblindness and/or is not true to the data, i.e. not perceptually uniform.

    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.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

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  3. Version published to 10.1101/2021.05.16.21257155v1 on medRxiv