TY - JOUR T1 - Aerosol emission from the respiratory tract: an analysis of aerosol generation from oxygen delivery systems JF - Thorax JO - Thorax DO - 10.1136/thoraxjnl-2021-217577 SP - thoraxjnl-2021-217577 AU - Fergus W Hamilton AU - Florence K A Gregson AU - David T Arnold AU - Sadiyah Sheikh AU - Kirsty Ward AU - Jules Brown AU - Ed Moran AU - Carrie White AU - Anna J Morley AU - AERATOR Group AU - Bryan R Bzdek AU - Jonathan P Reid AU - Nicholas A Maskell AU - James William Dodd Y1 - 2021/11/02 UR - http://thorax.bmj.com/content/early/2021/11/01/thoraxjnl-2021-217577.abstract N2 - Introduction continuous positive airway pressure (CPAP) and high-flow nasal oxygen (HFNO) provide enhanced oxygen delivery and respiratory support for patients with severe COVID-19. CPAP and HFNO are currently designated as aerosol-generating procedures despite limited high-quality experimental data. We aimed to characterise aerosol emission from HFNO and CPAP and compare with breathing, speaking and coughing.Materials and methods Healthy volunteers were recruited to breathe, speak and cough in ultra-clean, laminar flow theatres followed by using CPAP and HFNO. Aerosol emission was measured using two discrete methodologies, simultaneously. Hospitalised patients with COVID-19 had cough recorded using the same methodology on the infectious diseases ward.Results In healthy volunteers (n=25 subjects; 531 measures), CPAP (with exhalation port filter) produced less aerosol than breathing, speaking and coughing (even with large >50 L/min face mask leaks). Coughing was associated with the highest aerosol emissions of any recorded activity. HFNO was associated with aerosol emission, however, this was from the machine. Generated particles were small (<1 µm), passing from the machine through the patient and to the detector without coalescence with respiratory aerosol, thereby unlikely to carry viral particles. More aerosol was generated in cough from patients with COVID-19 (n=8) than volunteers.Conclusions In healthy volunteers, standard non-humidified CPAP is associated with less aerosol emission than breathing, speaking or coughing. Aerosol emission from the respiratory tract does not appear to be increased by HFNO. Although direct comparisons are complex, cough appears to be the main aerosol-generating risk out of all measured activities.All data relevant to the study are included in the article or uploaded as supplemental information. Anonymised aerosol data from the AERATOR Study will be submitted to the Bristol data repository (data.bris.ac.uk) on completion of the full study. ER -