Reducing Risk of Nosocomial COVID— Time to Revisit Aerosol Generating Procedures and Admission Testing?

Reviewed by Cindy Noyes, MD, University of Vermont Medical Center

Zhang and colleagues performed a systematic review of 24 observational and experimental studies evaluating aerosol generation by subjects receiving various respiratory therapies, such as high flow nasal oxygen, continuous and bilevel positive airway pressure compared to normal breathing or use of nasal cannula.1  The studies included normal subjects and infected patients with varied pathogens.1  Outcomes of interest included identification of pathogens in air samples (via culture or RNA/DNA) and number of small aerosols created.1  There was no association of increased airborne pathogen detection with non-invasive respiratory therapies and as such no differential protective measures recommended for healthcare workers (HCW) based on exposure to patients receiving hi-flow or non-invasive ventilation, potentially reducing unnecessary airborne isolation and respirator use.1 

Hatfield and colleagues describe a cohort using a large US database to assess hospital onset (HO) COVID and potential association with hospital factors, community incidence, predominant variant in circulation.2  The study was conducted from July 2020-June 2022 and included 5687 hospital months from 288 different hospitals.2  Patients with positive COVID tests prior to and at time of admission were considered community onset (CO), hospital days 4-7 indeterminate and after day 7, hospital onset.2  Rates of HO COVID occurred in similar frequency as compared to other healthcare associated infections (HAI) and trended up and down with CO cases.2  In fact, a 10% increase in proportion of all hospitalizations with CO COVID was associated with a 178% increase in HO COVID.2  Mean hospital onset rates of infection were lowest in those facilities that tested less frequently (less than 25% of admissions).2  However, in adjusted models (considering proportion of CO COVID, variant, admission testing rate, bed size and geographic census), hospitals that tested more than 50% of their admissions were associated with a 13% decrease in HO COVID cases as compared to those who tested 25-50% of admissions.2  This suggests that mitigation strategies, including testing, may be most effective when community prevalence of COVID is high. 


  • Zhang M, et al.  Generation of aerosols by non invasive respiratory support moalilties: A systematic review and meta-analysis.  JAMA Network Open.  2023; 6(10):e.2337258
  • Hatfield K, et al.  Assessment of hospital onset SARS CoV-2 infection rates and testing practices in the US, 2020-2022.  JAMA Network Open.  2023; 6(8):e2329441.
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