key: cord-0766822-wa3s35jp authors: Janssen, Matthijs L.; Klazen, Yoram P.; de Man, Peter; Hanselaar, Wessel; Ong, David S.Y.; Wils, Evert-Jan title: Airborne SARS-CoV-2 RNA excretion by patients with COVID-19 on different oxygen delivery systems: a prospective observational study date: 2022-03-12 journal: J Hosp Infect DOI: 10.1016/j.jhin.2022.03.001 sha: b2f7fa3501297008eb1eedd39482e7d06d39321b doc_id: 766822 cord_uid: wa3s35jp Concerns persist on the risk of airborne SARS-CoV-2 transmission by patients with COVID-19 on various modalities of oxygen therapy, like high flow nasal cannula (HFNC). We aimed to compare the presence of airborne RNA in air samples between groups of patients with COVID-19 on different oxygen delivery systems. We also explored factors that were associated with SARS-CoV-2 RNA positivity in air samples. Air samples were positive for SARS-CoV-2 RNA in three out of 39 patients (8%) on HFNC, null out of 13 (0%) on masks, versus five out of 20 (25%) on nasal cannula. Odds ratio for air sample positivity was 0.52 (95% CI 0.11-2.34) when comparing HFNC vs. non-HFNC group, and 5.78 (1.24-27.01) for nasal cannula vs non-nasal cannula group. Patients with positive air samples in comparison to those with negative air samples were sampled earlier after symptoms onset (median: 7 vs. 10 days; p=0.04) and had lower Ct values of diagnostic nasopharyngeal samples (median: 22 vs. 26; p=0.02). In conclusion, air sample positivity was not related to oxygen support device but to viral load. These data suggest that the use of personal protection equipment should be based on risk management according to viral load rather than oxygen support device. Hypoxemia in patients with Coronavirus Disease 2019 (COVID-19) can be treated with a variety of oxygen delivery systems. Concerns however persist on their potential aggravating role in airborne Severe Acute Respiratory Syndrome Corona Virus-2 (SARS-CoV-2) transmission. High-Flow Nasal Cannula (HFNC) oxygen therapy appears clinically beneficial for patients with COVID-19 but was discouraged earlier in the pandemic because of its aerosol-generating potential [1, 2] . Accumulating non-clinical data indicate that HFNC is not associated with more dispersion of aerosols and large droplets compared to conventional oxygen delivery systems [3] . Studies on airborne SARS-CoV-2 Ribonucleic acid (RNA) dispersion in patients with COVID-19 are however limited and have scarcely addressed the role of different oxygen delivery systems. In the present clinical study, our main objective was to examine whether HFNC is associated with more frequent detection of SARS-CoV-2 RNA as compared to other oxygen delivery systems in air samples in the proximity of hospitalised patients with COVID-19. In addition, we explored what factors were associated with airborne viral RNA positivity. This clinical study was performed from February to May 2021. The local institutional review board (IRB) declared that this study does not fall within the scope of the Dutch Medical Research involving human subjects act (IRB protocol number 2021-029). Patients were informed about the study and were asked oral consent. Paykel Healthcare). During the study period hypoxemic patients with COVID-19 were initially treated by nasal cannula. If support was insufficient treatment was escalated to HFNC, sometimes preceded by air-entrainment or non-rebreathing masks. Dexamethasone was initiated in patients when therapy was escalated to oxygen administration, and a single dose of interleukin-6 receptor antagonist (tocilizumab) was administered when HFNC was started (as of February 2021). The methodology of air sampling, RNA harvesting from filters and quantitative reverse transcription PCR (RT-qPCR) has been described previously [4] . In short, an IIR type surgical face mask (Romed Holland, type MASK-L) was used as sample filter placed on the hose inlet of a vacuum cleaner (Nilfisk household vacuum cleaner, with HEPA filter). Air samples were collected by investigators wearing personal protection equipment (PPE) in the ward or Intensive Care Unit (ICU). All rooms were equipped with mechanical room ventilation with an air-exchange rate of six air changes per hour. Air was sampled for 2.5 minutes at two separate locations sequentially ( Figure S2 ): 50 centimetres (cm) behind and 30cm above the patient's head (dorsal sample; harvesting aerosols only) and 50cm in front and 30cm below (ventral sample; harvesting both droplets and aerosols). The marked circle of the sampling face mask was cut out, RNA was extracted using the Roche MagNa Pure large volume total nucleic acid extracting kit. Sample filters were analysed on our validated in-house RT-qPCR assay on the presence of SARS-CoV-2 RNA and Cycle threshold (Ct) values were determined. Demographic, clinical, laboratory (including the 4C Mortality prognostic score [5] ) and PCR data were recorded. Environmental circumstances, patient's behaviour and clinical condition were scored prior to and during sampling. The 24 hours prior to sampling cough severity was scored using the Fisman cough severity score, and cough and sneezing frequency by a Numerated Rating Scale (NRS; 0: no coughing/sneezing; 10: continuous coughing/sneezing). During sampling mouth opening, speaking, sneezing, coughing (yes/no; number of coughs/2.5 minutes; Fisman cough severity) and vital parameters like respiratory rate were recorded. Groups were compared using Mann-Whitney-U test for continuous variables and Fisher's exact test In total, 150 samples of seventy-five patients were analysed (Table 1a) . 20 patients were on nasal cannula, 13 on air-entrainment mask, 3 on non-rebreathing mask and 39 on HFNC (n=19 flow 40L/min; n=20 patients flow 60L/min). Patients were sampled in the ICU (31%) or respiratory ward (69%). As part of standard care, all patients received dexamethasone and twenty-seven (69%) patients on HFNC received a single dose of tocilizumab prior to sampling. Four out of 75 patients had received a first SARS-CoV-2 vaccination dose, whereas others were not (yet) vaccinated. Table 2) . Median Ct-values of diagnostic PCR and symptom duration until sampling did not differ between groups on different oxygen delivery systems. Air samples were positive in five out of 20 patients (25%) on nasal cannula, in null out of 13 patients (0%) on air-entrainment or NRM, and in three out of 39 patients (8%) on HFNC ( Table 1a) . The proportion of patients with positive air samples was not higher for the HFNC group compared to different non-HFNC modality groups (Table 1b) . In contrast, the proportion of positive samples was higher in the nasal cannula group compared to different nonnasal cannula groups. This is the first real-life clinical study comparing SARS-CoV-2 RNA dispersion between different oxygen delivery systems in a large sample of hospitalised patients with COVID-19. In our analysis, the use of HFNC was not associated with more frequent detection of airborne viral RNA surrounding patients in a well-ventilated hospital environment. In contrast, the use of nasal cannula appeared to be associated with more frequent detection. An explanation for the observed difference may be the shorter duration between symptom onset and sampling, and higher nasopharyngeal viral load in patients on nasal cannula. Our airborne viral RNA data extend the evidence from imaging studies, arguing that HFNC does not enhance aerosols and droplet dispersion [3, 6] . Ideally the next step would be to use viral culturing of air sample to compare the effect of different delivery systems more definitively. This technique however remains technically challenging and is currently not feasible for large scale use, making viral RNA air sampling the most useful method currently available [7] . The observed correlation between high nasopharyngeal viral load (associated with a shorter duration of symptoms and nasal cannula use) and airborne viral RNA detection is in line with studies underscoring the role of high viral load early in the disease course and transmissibility [8] . Of note, in our previous study SARS-CoV-2 RNA was more frequently detected in up to 70% of samples obtained in poorly ventilated households of recently infected healthcare workers as compared to only 23% in a well-ventilated ICU-setting during potential aerosol-generating medical procedures [4] . We also observed that air samples were as frequently positive when obtained in the dorsal sampling position (where the contribution of large droplets is presumed negligible) as in ventral position supporting accumulating data on the role of aerosols as vectors of SARS-CoV-2 [9] . The patients included in our current study were predominantly infected with the alpha VOC, and only a minority had received a first dose of SARS-CoV-2 vaccine. The delta and omicron VOCs are associated with increased transmission rates, that possibly relate to the level of viral load (as measured by PCR or culture) in the upper airways. Ample evidence indicates that vaccination reduces transmission rate but its J o u r n a l P r e -p r o o f relation to nasopharyngeal viral load is less clear [10] [11] [12] . The influence of vaccination and different VOC on viral aerosolisation are important knowledge gaps that need to be addressed in future studies. These studies can take advantage of the easy-to-use air sampling methodology as applied in the current study. Several limitations of our study need consideration. First, this was a non-experimental clinical study precluding a direct comparison between oxygen delivery systems with correction for confounders such as nasopharyngeal viral load and duration of symptoms. Although our sample size was considerable and the largest among similar studies, the event rate was too small for multivariable analysis. Nevertheless, we believe our real-life study is relevant as the strategy for escalating oxygen therapy mirrors contemporary clinical practice in COVID-19. Second, we could not investigate the association between the presence or quantity of airborne viral RNA and risk of transmission. Such investigation requires a larger sample size and meticulous contact-tracing. Third, we did not adjust our analysis for hazardous manoeuvres like coughing, sneezing and vocation. Such manoeuvres, in addition to the level of ventilation and the level of patient's infectivity may well be more relevant for viral transmission risk than the oxygen delivery system itself [3, 13, 14] . In the current study, patients' behaviour and environmental circumstances were similar for patients with positive versus negative air samples ( Table 2) , suggesting no or only limited interference with our study results. In conclusion, the risk of airborne SARS-CoV-2 RNA detection was not higher in patients on HFNC in comparison to other oxygen delivery systems. More recent infection and higher viral load, at the moment of diagnostic sampling in patients on nasal cannula most likely contribute to the observed higher rate of viral dispersion. Our results emphasize that (in-hospital) use of PPE should be regarded equally important when nasal cannulas are used early during the disease course as compared to settings with possible aerosol-generating oxygen delivery systems like HFNC. J o u r n a l P r e -p r o o f Wils takes responsibility for (is the guarantor of) the content of the manuscript, including the data and analysis. The following authors are responsible for the various aspects of the manuscript Wils: design of the work Wils: acquisition, analysis, & interpretation of data for the work Protecting healthcare workers from SARS-CoV-2 infection: practical indications Effect of High-Flow Oxygen Therapy vs Conventional Oxygen Therapy on Invasive Mechanical Ventilation and Clinical Recovery in Patients With Severe COVID-19: A Randomized Clinical Trial Aerosol Generation from the Respiratory Tract with Various Modes of Oxygen Delivery Airborne SARS-CoV-2 in home-and hospital environment investigated with a high-powered air sampler Risk stratification of patients admitted to hospital with covid-19 using the ISARIC WHO Clinical Characterisation Protocol: development and validation of the 4C Mortality Score Aerosol generating procedures: are they of relevance for transmission of SARS-CoV-2? Collection, particle sizing and detection of airborne viruses Transmission of COVID-19 in 282 clusters in Catalonia, Spain: a cohort study Ten scientific reasons in support of airborne transmission of SARS-CoV-2 Infection with the SARS-CoV-2 Delta Variant is Associated with Higher Recovery of Infectious Virus Compared to the Alpha Variant in both Unvaccinated and Vaccinated Individuals Prevention of host-to-host transmission by SARS-CoV-2 vaccines Infectious viral load in unvaccinated and vaccinated patients infected with SARS-CoV-2 WT, Delta and Omicron Heterogeneity in transmissibility and shedding SARS-CoV-2 via droplets and aerosols Small droplet aerosols in poorly ventilated spaces and SARS-CoV-2 transmission We would like to thank the medical microbiology laboratory technicians of the Franciscus Gasthuis & Vlietland hospital, in particular Han Veltman, Gerda Doejaaren, and Dick Wille, and team managers for their assistance in performing the experiments. We would like to thank Rene Bakker for the pictures used in Figure S1 and Figure S2 . Informed consent was obtained from the persons in Figure S1 and S2.J o u r n a l P r e -p r o o f The authors have no relevant financial or non-financial interests to disclose.