Table I.

Risk of nosocomial transmission with aerosol-generating procedures with SARS-CoV-2

Procedure	Studies	Findings	Quality	References
Intubation	Eight observational studies in three countries investigating risk of SARS transmission to exposed HCWs.	Significant increase in risk of transmission seen in six studies. Combined odds ratio of 6.6 reported in meta-analysis.	Low –Conclusions extrapolated from SARS –Small retrospective studies only –Consistent findings shown	[[27], [28], [29], [30], [31], [32], [33], [34], [35]]
Tracheotomy, CPR and manual ventilation	Five studies in two countries investigating risk of SARS transmission to exposed HCWs.	No clear increase in infection risk. Only one study analysed tracheotomy and found a significantly increased transmission risk but this was not seen in multivariate analysis. Three out of four studies suggested an increased infection risk associated with resuscitation (chest compression or pre-intubation ventilation) but could not separate effect of these procedures from intubation. No significant effect was seen associated with defibrillation.	Very low –Conclusions extrapolated from SARS –Small retrospective studies only –Inconsistent findings –Confounding variables not accounted for.	[[28], [29], [30],32,36]
Bronchoscopy and airway suctioning	Two cohort studies in one country investigating risk of SARS transmission to exposed HCWs. One study tested for presence of influenza RNA in aerosols from patient rooms during AGPs.	No clear increase in risk. Neither SARS study showed significant increased risk of infection with bronchoscopy or any effect of airway suctioning. Bronchoscopy was the only AGP associated with increased probability of influenza detection in aerosols.	Very low –Conclusions extrapolated from SARS and influenza –Uncertain significance of indirect finding of RNA detection –Very small studies only –Inconsistent and imprecise results	[28,29,37]
Non-invasive ventilation (NIV)	Four observational studies from two countries investigating risk of SARS transmission. One further study examining dispersal of air during NIV and another measuring aerosols/droplets produced.	No clear increase in risk has been demonstrated. Three studies showed a trend towards increased risk of SARS transmission, two results were statistically significant (although not upheld in multivariate analysis). The fourth study showed no infections in 105 HCWs exposed to NIV although they did not assess risk in non-exposed workers. Air dispersal was detected to ∼1 m but no significant increase in aerosol production was shown.	Very low –Conclusions extrapolated from SARS –Small studies only –Inconsistent results –Uncertain significance of indirect finding such as air dispersal and aerosol production in healthy volunteers	[28,38,39,30,40,31]
High-flow nasal canulae (HFNC) and oxygen masks	Two observational studies from one country investigating risk of SARS transmission looked at manipulation of oxygen masks (one of which also looked at HFNC). One randomized control trial compared effect of HFNC vs oxygen masks on bacterial cultures in rooms of patients with bacterial pneumonia	Both studies showed a small trend towards increased risk with manipulation of oxygen mask (the small study showed a significant effect). HFNC was not shown to have a significant effect. No difference in bacterial count between HFNC and oxygen masks was demonstrated.	Very low –Conclusions extrapolated from SARS and bacterial infections –Small studies only –Inconsistent results –Confounding variables not accounted for –Uncertain significance of indirect findings regarding bacterial cultures	[28,29,41]
Nebulizer treatment	Three observational studies from two countries investigating risk of SARS transmission. An additional study measured aerosol dispersal during nebulizer use.	Two studies showed a correlation but both were small and neither showed a significant increase in infection risk. Significantly increased numbers of aerosols were detected at 1 m distance from patients during nebulizer use.	Very low –Conclusions extrapolated from SARS –Very small studies –Inconsistent results and wide confidence intervals –Finding of aerosol production during nebulizer use is unlikely to be clinically important	[28,29,42,43]
Nasopharyngeal swabbing and collection of sputum	One observational study investigating risk of SARS transmission assessed collection of sputum.	No significant effect on infection risk was seen (four infected out of 42 exposed).	Very low –Conclusions extrapolated from SARS –Very small study –Wide confidence interval –No evidence regarding nasopharyngeal swabbing	[28]
Endoscopy and transoesophageal echocardiography	One prospective study investigating bacterial growth from facemasks used during endoscopies.	Significantly increased colony-forming units detected post endoscopy compared to controls.	Very low –Conclusion extrapolated from study of bacteria –Indirect study with regard to aerosol transmission	[44]

SARS-CoV-2, severe acute respiratory syndrome coronavirus-2; HCWs, healthcare workers; CPR, cardiopulmonary resuscitation; AGP, aerosol-generating procedure.