The use of continuous positive airway pressure (CPAP) or high-flow nasal oxygen (HFNO) to treat moderate/severe COVID-19 does not produce significant additional air or surface viral contamination compared with supplemental oxygen, according to an observational study published in Thorax.

CPAP and HFNO devices are associated with reductions in mortality and progression to intubation for hypoxemic respiratory failure; however, they are considered “aerosol-generating procedures” in the treatment of COVID-19. Few studies have evaluated their transmission risk to healthcare workers.

To better understand the risks of airborne and fomite SARS-CoV-2 contamination and exposure to healthcare workers, researchers sampled the clinical environment of 30 hospitalized patients with COVID-19 undergoing either supplemental oxygen, CPAP, or HFNO (n=10 in each group). Researchers collected a nasopharyngeal swab and 3 air and 3 surface samples from each patient and the clinical environment. Of these patients, 70% (n=21) tested positive for SARS-CoV-2 RNA in the nasopharynx. Of all of the air and surface samples, only 4/90 (4%) and 6/90 (7%) tested positive for viral RNA, respectively. The researchers noted that there were an additional 10 suspected-positive samples in both air and surfaces samples; however, they did not find biologically viable virus in cell culture from any positive or suspected-positive samples except for 1 nasopharyngeal sample from a HFNO patient.

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“We found limited SARS-CoV-2 viral RNA within the immediate environment of hospitalised patients with COVID-19, and that this did not appear to be substantially influenced by the use of CPAP/HFNO devices or coughing, and importantly, no detectable biologically viable virus,” concluded the authors. Thus, it is more likely that healthcare worker exposure and nosocomial transmission is a result of patient factors, such as coughing at earlier stages of infection, rather than the type of respiratory support used for treatment.


Winslow RL, Zhou J, Windle EF, et al. SARS-CoV-2 environmental contamination from hospitalised patients with COVID-19 receiving aerosol-generating procedures. Thorax. Published online November 4, 2021. doi:10.1136/thoraxjnl-2021-218035