Aerosol generation during percutaneous tracheostomy insertion

Brown

Gregson

et al. 2021

Preprint

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.

Section: Discussionmentioning

confidence: 99%

“…Several recent studies have questioned whether these medical procedures should be classified as 'aerosol-generating' following quantitation of the aerosol produced during these patient care activities [11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

A quantitative evaluation of aerosol generation during manual facemask ventilation

Brown

Gregson

et al. 2021

Preprint

“…The categorisation of OGD as an AGP was not based on evidence demonstrating aerosol generation from this intervention, nor from being associated with an increased incidence of SARS-CoV-2 transmission to healthcare workers conducting the procedures. Recent work directly measuring aerosol levels in the clinical environment has questioned the validity of inclusion of several procedures defined as ‘aerosol generating’ including tracheal intubation and extubation 20 , percutaneous tracheostomy 21 and respiratory supportive treatments such as continuous positive airway pressure delivered via a facemask. 22–24 …”

Section: Introductionmentioning

confidence: 99%

Identification of the source events for aerosol generation during oesophago-gastro-duodenoscopy

Gregson

Hamilton

et al. 2021

Gut

Self Cite

ObjectiveTo determine if oesophago-gastro-duodenoscopy (OGD) generates increased levels of aerosol in conscious patients and identify the source events.DesignA prospective, environmental aerosol monitoring study, undertaken in an ultraclean environment, on patients undergoing OGD. Sampling was performed 20 cm away from the patient’s mouth using an optical particle sizer. Aerosol levels during OGD were compared with tidal breathing and voluntary coughs within subject.ResultsPatients undergoing bariatric surgical assessment were recruited (mean body mass index 44 and mean age 40 years, n=15). A low background particle concentration in theatres (3 L−1) enabled detection of aerosol generation by tidal breathing (mean particle concentration 118 L−1). Aerosol recording during OGD showed an average particle number concentration of 595 L−1 with a wide range (3–4320 L−1). Bioaerosol-generating events, namely, coughing or burping, were common. Coughing was evoked in 60% of the endoscopies, with a greater peak concentration and a greater total number of sampled particles than the patient’s reference voluntary coughs (11 710 vs 2320 L−1 and 780 vs 191 particles, n=9 and p=0.008). Endoscopies with coughs generated a higher level of aerosol than tidal breathing, whereas those without coughs were not different to the background. Burps also generated increased aerosol concentration, similar to those recorded during voluntary coughs. The insertion and removal of the endoscope were not aerosol generating unless a cough was triggered.ConclusionCoughing evoked during OGD is the main source of the increased aerosol levels, and therefore, OGD should be regarded as a procedure with high risk of producing respiratory aerosols. OGD should be conducted with airborne personal protective equipment and appropriate precautions in those patients who are at risk of having COVID-19 or other respiratory pathogens.

“…Procedures' or better even to reassess use of the term at all [11]. This term places the emphasis of risk on the medical procedure (many of which have been demonstrated not to generate aerosol [6,[16][17][18][19]) 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 SARS-CoV-2), the proximity of the operator to the patient's respiratory tract, the duration of this proximity, the health, immune and vaccination status of the operator and the environment in which the interaction occurs.…”

Section: Discussionmentioning

confidence: 99%

A quantitative evaluation of aerosol generation from upper airway suctioning during tracheal intubation and extubation sequences

Brown

Cook

et al. 2021

Preprint

Background: Open respiratory suctioning is considered to be an aerosol generating procedure (AGP) and laryngopharyngeal suction, used to clear secretions during anaesthesia, is widely managed as an AGP. It is uncertain whether such upper airway suctioning should be designated an aerosol generating procedure (AGP) because of a lack of both aerosol and epidemiological evidence of risk. Aim: To assess the relative risk of aerosol generation by upper airway suction during tracheal intubation and extubation in anaesthetised patients. Methods: Prospective environmental monitoring study in ultraclean operating theatres to assay aerosol concentration during intubation and extubation sequences including upper airway suctioning for patients undergoing surgery (n=19 patients). An Optical Particle Sizer (particle size 300nm-10μm) was used to sample aerosol 20cm above the mouth of the patient. Baseline recordings (background, tidal breathing and volitional coughs) were followed by intravenous induction of anaesthesia with neuromuscular blockade. Four periods of oropharyngeal suction were performed with a Yankauer sucker: pre-laryngoscopy, post-intubation and pre- and post-extubation. Findings: Aerosol from breathing was reliably detected (65[39-259] particles.L-1 (median[IQR])) above background (4.8[1-7] particles.L-1, p<0.0001 Friedman). The procedure of upper airway suction was associated with much lower average concentrations of aerosol than breathing (6.0[0-12] particles.L-1, P=0.0007) and was indistinguishable from background (P>0.99). The peak aerosol concentration recorded during suctioning (45[30-75] particles.L-1) was much lower than both volitional coughs (1520[600-4363] particles.L-1, p<0.0001, Friedman) and tidal breathing (540[300-1826] particles.L-1, p<0.0001, Friedman). Conclusion: The procedure of upper airway suction during airway management is associated with no higher concentration of aerosol than background and much lower than breathing and coughing. Upper airway suction should not be designated as a high risk AGP.