• Forbes McGain, Ruhi S Humphries, Jung Hoon Lee, Robyn Schofield, Craig French, Melita D Keywood, Louis Irving, Kevin Kevin, Jim Patel, and Jason Monty.
• Western Health, Melbourne, VIC, Australia. Forbes.McGain@wh.org.au.
• Crit Care Resusc. 2020 Sep 1; 22 (3): 212220212-220.

ObjectiveTo quantify aerosol generation from respiratory interventions and the effectiveness of their removal by a personal ventilation hood.Design And SettingDetermination of the aerosol particle generation (in a single, healthy volunteer in a clean room) associated with breathing, speaking, wet coughing, oxygen (O2) 15 L/min via face mask, O2 60 L/min via nasal prongs, bilevel non-invasive positive-pressure ventilation (BiPAP) and nebulisation with O2 10 L/min.InterventionsAerosol generation was measured with two particle sizer and counter devices, focusing on aerosols 0.5-5 μm (human-generated aerosols), with and without the hood. An increase from baseline of less than 0.3 particles per mL was considered a low level of generation.Main Outcome MeasuresComparisons of aerosol generation between different respiratory interventions. Effectiveness of aerosol reduction by a personal ventilation hood.ResultsResults for the 0.5-5 μm aerosol range. Quiet breathing and talking demonstrated very low increase in aerosols (< 0.1 particles/mL). Aerosol generation was low for wet coughing (0.1 particles/mL), O2 15 L/min via face mask (0.18 particles/mL), and high flow nasal O2 60 L/min (0.24 particles/mL). Non-invasive ventilation generated moderate aerosols (29.7 particles/mL) and nebulisation very high aerosols (1086 particles/mL); the personal ventilation hood reduced the aerosol counts by 98% to 0.5 particles/mL and 8.9 particles/mL respectively.ConclusionsIn this human volunteer study, the administration of O2 15 L/min by face mask and 60 L/min nasal therapy did not increase aerosol generation beyond low levels. Non-invasive ventilation caused moderate aerosol generation and nebulisation therapy very high aerosol generation. The personal ventilation hood reduced the aerosol counts by at least 98%.

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