Quantitative evaluation of aerosol generation during manual facemask ventilation

A J Shrimpton; J M Brown; F K A Gregson; T M Cook; D A Scott; F McGain; R S Humphries; R S Dhillon; J P Reid; F Hamilton; B R Bzdek; A E Pickering; AERATOR study group

doi:10.1111/anae.15599

Quantitative evaluation of aerosol generation during manual facemask ventilation

Anaesthesia. 2022 Jan;77(1):22-27. doi: 10.1111/anae.15599. Epub 2021 Oct 26.

Authors

A J Shrimpton¹, J M Brown², F K A Gregson³, T M Cook⁴, D A Scott⁵, F McGain⁶, R S Humphries⁷, R S Dhillon⁸, J P Reid³, F Hamilton⁹, B R Bzdek³, A E Pickering¹; AERATOR study group

Collaborators

AERATOR study group:
C White, J Murray, D Arnold, G Nava, N Maskell, J Dodd, E Moran, J Keller, M Gormley, S Sheikh, A Davidson

Affiliations

¹ Anaesthesia, Pain and Critical Care Sciences, School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK.
² Department of Anaesthesia and Intensive Care Medicine, North Bristol NHS Trust, Bristol, UK.
³ School of Chemistry, University of Bristol, Bristol, UK.
⁴ Department of Anaesthesia and Intensive Care Medicine, Royal United Hospital NHS Trust, Bath, UK.
⁵ Department of Critical Care, University of Melbourne; St. Vincent's Hospital Melbourne, Australia.
⁶ Western Health, Footscray, Victoria, Australia.
⁷ Climate Science Centre, CSIRO Oceans and Atmosphere, Aspendale, Victoria, Australia.
⁸ Department of Neurosurgery, St Vincent's Hospital Melbourne, Fitzroy, Victoria, Australia.
⁹ Department of Population Health Sciences, University of Bristol, Bristol, UK.

Abstract

Manual facemask ventilation, a core component of elective and emergency airway management, is classified as an aerosol-generating procedure. This designation is based on one epidemiological study suggesting an association between facemask ventilation and transmission during the SARS-CoV-1 outbreak in 2003. There is no direct evidence to indicate whether facemask ventilation is a high-risk procedure for aerosol generation. We conducted aerosol monitoring during routine facemask ventilation and facemask ventilation with an intentionally generated leak in anaesthetised patients. Recordings were made in ultraclean operating theatres and compared against the aerosol generated by tidal breathing and cough manoeuvres. Respiratory aerosol from tidal breathing in 11 patients was reliably detected above the very low background particle concentrations with median [IQR (range)] particle counts of 191 (77-486 [4-1313]) and 2 (1-5 [0-13]) particles.l^-1 , respectively, p = 0.002. The median (IQR [range]) aerosol concentration detected during facemask ventilation without a leak (3 (0-9 [0-43]) particles.l^-1 ) and with an intentional leak (11 (7-26 [1-62]) particles.l^-1 ) was 64-fold (p = 0.001) and 17-fold (p = 0.002) lower than that of tidal breathing, respectively. Median (IQR [range]) peak particle concentration during facemask ventilation both without a leak (60 (0-60 [0-120]) particles.l^-1 ) and with a leak (120 (60-180 [60-480]) particles.l^-1 ) were 20-fold (p = 0.002) and 10-fold (0.001) lower than a cough (1260 (800-3242 [100-3682]) particles.l^-1 ), respectively. This study demonstrates that facemask ventilation, even when performed with an intentional leak, does not generate high levels of bioaerosol. On the basis of this evidence, we argue facemask ventilation should not be considered an aerosol-generating procedure.

Keywords: COVID-19; SARS-CoV-2; aerosol-generating procedure; facemask ventilation; manual ventilation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Aged
Cough / etiology
Female
Humans
Male
Masks*
Middle Aged
Respiratory Aerosols and Droplets / chemistry*
Severe Acute Respiratory Syndrome / pathology
Severe Acute Respiratory Syndrome / virology
Severe acute respiratory syndrome-related coronavirus / isolation & purification

Associated data

ISRCTN/N21447815

Abstract

Publication types

MeSH terms

Associated data

Grants and funding