The effect of respiratory activity, non‐invasive respiratory support and facemasks on aerosol generation and its relevance to COVID‐19

  • N. M. Wilson
    Department of Intensive Care Medicine Prince of Wales Hospital Sydney Australia
  • G. B. Marks
    Department of Respiratory Medicine University of New South Wales Sydney Australia
  • A. Eckhardt
    Department of Intensive Care Medicine Prince of Wales Hospital Sydney Australia
  • A. M. Clarke
    Department of Intensive Care Royal Prince Alfred Hospital Sydney Australia
  • F. P. Young
    Department of Intensive Care Medicine Prince of Wales Hospital Sydney Australia
  • F. L. Garden
    University of New South Wales Sydney Australia
  • W. Stewart
    Department of Intensive Care Medicine Prince of Wales Hospital Sydney Australia
  • T. M. Cook
    Department of Anaesthesia and Intensive Care Medicine Royal United Hospitals NHS Trust Bath UK
  • E. R. Tovey
    Woolcock Institute of Medical Research University of Sydney Australia

抄録

<jats:title>Summary</jats:title><jats:p>Respirable aerosols (< 5 µm in diameter) present a high risk of SARS‐CoV‐2 transmission. Guidelines recommend using aerosol precautions during aerosol‐generating procedures, and droplet (> 5 µm) precautions at other times. However, emerging evidence indicates respiratory activities may be a more important source of aerosols than clinical procedures such as tracheal intubation. We aimed to measure the size, total number and volume of all human aerosols exhaled during respiratory activities and therapies. We used a novel chamber with an optical particle counter sampling at 100 l.min<jats:sup>‐1</jats:sup> to count and size‐fractionate close to all exhaled particles (0.5–25 µm). We compared emissions from ten healthy subjects during six respiratory activities (quiet breathing; talking; shouting; forced expiratory manoeuvres; exercise; and coughing) with three respiratory therapies (high‐flow nasal oxygen and single or dual circuit non‐invasive positive pressure ventilation). Activities were repeated while wearing facemasks. When compared with quiet breathing, exertional respiratory activities increased particle counts 34.6‐fold during talking and 370.8‐fold during coughing (p < 0.001). High‐flow nasal oxygen 60 at l.min<jats:sup>‐1</jats:sup> increased particle counts 2.3‐fold (p = 0.031) during quiet breathing. Single and dual circuit non‐invasive respiratory therapy at 25/10 cm.H<jats:sub>2</jats:sub>O with quiet breathing increased counts by 2.6‐fold and 7.8‐fold, respectively (both p < 0.001). During exertional activities, respiratory therapies and facemasks reduced emissions compared with activities alone. Respiratory activities (including exertional breathing and coughing) which mimic respiratory patterns during illness generate substantially more aerosols than non‐invasive respiratory therapies, which conversely can reduce total emissions. We argue the risk of aerosol exposure is underappreciated and warrants widespread, targeted interventions.</jats:p>

収録刊行物

  • Anaesthesia

    Anaesthesia 76 (11), 1465-1474, 2021-03-30

    Wiley

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