A quantitative evaluation of aerosol generation during manual facemask ventilation

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 a single epidemiological study suggesting an association between facemask ventilation and transmission from the SARS 2003 outbreak. 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 with neuromuscular blockade. Recordings were made in ultraclean theatres and compared against the aerosol generated by the patient during their own tidal breathing and coughs. Respiratory aerosol from tidal breathing was reliably detected above the very low background particle concentrations (191 (77–486 [3.8–1313]) versus 2.1 (0.7–4.6 [0–12.9] particles/L median(IQR)[range], n=11, p=0.002). The average aerosol concentration detected during facemask ventilation both without a leak (3.0 particles/L (0–9 [0-43])) and with an intentional leak (11 particles/L (7.0 – 26 [1–62])) was 64–fold and 17–fold lower than that of tidal breathing (p=0.001 and p=0.002 respectively). The peak particle concentration during facemask ventilation both without a leak (60 particles/L (0 – 60 [0–120])) and with a leak (120 particles/L (60 – 180 [60–480]) were respectively 20–fold and 10–fold lower than a cough (1260 particles/L (800 – 3242 [100–3682]), p=0.002 and p=0.001 respectively). This study demonstrates that facemask ventilation, even performed with an intentional leak, does not generate high levels of bioaerosol. On the basis of this evidence, facemask ventilation should not be considered an aerosol generating procedure.

Quantitative evaluation of aerosol generation from upper airway suctioning assessed during tracheal intubation and extubation sequences in anaesthetized patients

“…During the conduct of this study, aerosol generation was recorded through 19 entire intubation sequences and 14 extubation sequences (including periods of facemask ventilation), which produced findings consistent with the authors' previous study with low levels of aerosol generation compared with cough [ 8 , 9 ]. In total, 19 patients were recruited to ensure that the study was adequately powered to detect differences during post-extubation suctioning, which was more difficult to obtain ( N =13).…”

“…These findings add further weight to the need to reassess the list of AGPs, and may be used to inform UK infection prevention and control guidance [ 3 , 13 ]. This places the emphasis of risk on the medical procedure (many of which have been demonstrated not to generate aerosol [ 9 , [19] , [20] , [21] , [22] ]) whilst neglecting multiple factors that should be considered during the risk of assessment of any patient interaction. The risk assessment should consider the likelihood of the patient being infected with a respiratory pathogen (such as severe acute respiratory syndrome coronavirus-2); the proximity of healthcare workers to the patient's respiratory tract; the duration of this proximity; the health, immune and vaccination status of the healthcare workers present; and the environment in which the interaction occurs.…”

“…A three-dimensional printed funnel [90-mm height, maximum diameter 75 mm, 10-mm exit port, formed of polylactic acid on a RAISE3D Pro2 Printer (3DGBIRE, Chorley, UK)] was attached to the OPS via a 1.25-m length of conductive silicone tubing (TSI Inc.). The authors have used this sampling methodology in previous studies investigating intubation, facemask ventilation, supraglottic airway use and oesophagoduodenoscopy [ 6 , [8] , [9] , [10] ]. The performance characteristics and aerosol sampling losses in the funnel/tubing have been characterized previously and shown to be relatively minor for respirable particles [ 11 ].…”

Complications associated with paediatric airway management during the COVID‐19 pandemic: an international, multicentre, observational study

“…Because airway management techniques are considered high risk for generating aerosols and droplets [15], many clinicians use physical barriers, in addition to traditional PPE, for protection during airway management. These barriers are highly controversial, with some clinicians decrying their use and others believing they are helpful [9, 16, 17].…”

“…Because airway management techniques are considered high risk for generating aerosols and droplets [15], many clinicians use physical barriers, in addition to traditional PPE, for protection during airway management.…”