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Airborne particle dispersion by high flow nasal oxygen: An experimental and CFD analysis.
Crowley, Caroline; Murphy, Brian; McCaul, Conan; Cahill, Ronan; Nolan, Kevin Patrick.
  • Crowley C; School of Mechanical and Material Engineering, University College Dublin, Dublin, Ireland.
  • Murphy B; Department of Anaesthesia, The Rotunda Hospital, Dublin, Ireland.
  • McCaul C; Department of Anaesthesia, Mater Misericordiae Hospital, Dublin, Ireland.
  • Cahill R; Department of Anaesthesia, The Rotunda Hospital, Dublin, Ireland.
  • Nolan KP; Department of Anaesthesia, Mater Misericordiae Hospital, Dublin, Ireland.
PLoS One ; 17(1): e0262547, 2022.
Article in English | MEDLINE | ID: covidwho-1643266
ABSTRACT
High Flow Nasal Oxygen (HFNO) therapy offers a proven means of delivering respiratory support to critically ill patients suffering from viral illness such as COVID-19. However, the therapy has the potential to modify aerosol generation and dispersion patterns during exhalation and thereby put healthcare workers at increased risk of disease transmission. Fundamentally, a gap exists in the literature with regards to the effect of the therapy on the fluid dynamics of the exhalation jet which is essential in understanding the dispersion of aerosols and hence quantifying the disease transmission risk posed by the therapy. In this paper, a multi-faceted approach was taken to studying the aerosol-laden exhalation jet. Schlieren imaging was used to visualise the flow field for a range of expiratory activities for three healthy human volunteers receiving HFNO therapy at flow rates of 0-60 L/min. A RANS turbulence model was implemented using the CFD software OpenFOAM and used to perform a parametric study on the influence of exhalation velocity and duration on the dispersion patterns of non-evaporating droplets in a room environment. A dramatic increase in the turbulence of the exhalation jet was observed when HFNO was applied. Quantitative analysis indicated that the mean exhalation velocity was increased by 2.2-3.9 and 2.3-3 times that for unassisted breathing and coughing, respectively. A 1-2 second increase was found in the exhalation duration. The CFD model showed that small droplets (10-40 µm) were most greatly affected, where a 1 m/s increase in velocity and 1 s increase in duration caused an 80% increase in axial travel distance.
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Full text: Available Collection: International databases Database: MEDLINE Main subject: Oxygen Inhalation Therapy / Particulate Matter Type of study: Prognostic study Limits: Humans Language: English Journal: PLoS One Journal subject: Science / Medicine Year: 2022 Document Type: Article Affiliation country: Journal.pone.0262547

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Full text: Available Collection: International databases Database: MEDLINE Main subject: Oxygen Inhalation Therapy / Particulate Matter Type of study: Prognostic study Limits: Humans Language: English Journal: PLoS One Journal subject: Science / Medicine Year: 2022 Document Type: Article Affiliation country: Journal.pone.0262547