Table 1 Studies of risk of airborne contamination from HFNC versus other forms of ventilatory support, in settings both directly and not directly related to SARS-CoV-2

From: Airborne spread of SARS-CoV-2 while using high-flow nasal cannula oxygen therapy: myth or reality?

Reference Ventilation techniques investigated Study design and size Relevant results
Studies directly related to SARS-COV-2
Guy T et al. (2020) High-flow nasal oxygen: a safe, efficient treatment for COVID-19 patients not in an ICU. Eur Respir J: 2,001,154 HFNC Clinical study (N = 27). Patients with RT-PCR-confirmed COVID-19 infection placed on HFNC for non-hypercapnic acute hypoxemic respiratory failure After a 30-day follow-up, only one nurse was infected with SARS-CoV-2 during the study period, potentially by domestic contact
Ahn JY et al. (2020) Environmental contamination in the isolation rooms of COVID-19 patients with severe pneumonia requiring mechanical ventilation or high-flow oxygen therapy. J Hosp Infect. S0195-6701(20)30,401–1 HFNC, NIV Clinical case series (N = 3). 3 patients with COVID-19 pneumonia (two mechanically ventilated, and one on HFNC/NIV) 13 of the 28 environmental samples in a room of a patient receiving HFNC/NIV showed positive results and viable virus. Air samples were negative for SARS-CoV-2
Studies not directly related to SARS-COV-2, testing various types of ventilatory support and interfaces: corroboration of risk
Leonard S et al. (2020) Reducing aerosol dispersion by high-flow therapy in COVID-19: High resolution computational fluid dynamics simulations of particle behavior during high velocity nasal insufflation with a simple surgical mask. J Am Coll Emerg Physicians Open. 1(4):578–591 HVNI, LFO2, and tidal breathing In silico computational fluid dynamics simulation evaluating particle and droplet behavior with use of Type 1 surgical masks Exhaled particulate mass capture by the mask was 88.8% (HVNI at 40L/min) vs 77.4% (LFO2 at 6 L/min). Particle distribution escaping to the room, (> 1 m from face) was 8.23% for HVNI + mask versus 17.2% for LFO2 + mask
 Leung CCH et al. (2019) Comparison of high-flow nasal cannula versus oxygen face mask for environmental bacterial contamination in critically ill pneumonia patients: a randomized controlled crossover trial. J Hosp Infect 101(1):84–87 HFNC at 60L/min, and OM at 8.6 ± 2.2 L/min Randomized controlled crossover trial (N = 20). Environmental contamination by viable bacteria in critically ill patients with Gram-negative pneumonia receiving HFNC or OM There were marginal differences in bacterial contamination between the HFNC and OM used
 Hui DS, (2015) Exhaled air dispersion during non-invasive ventilation via helmets and a total facemask. Chest. 147: 1336–1343 NIV via two different helmets via a ventilator and total facemask via a bilevel positive airway pressure device Preclinical study using human patient simulator During NIV via a helmet with the lung simulator programmed in mild lung injury, exhaled air leaked through the neck-helmet interface with a radial distance of 150 to 230 mm when inspiratory positive airway pressure was increased from 12 to 20 cmH20. During NIV via a helmet with air cushion around the neck, there was negligible air leakage. During NIV via a total facemask for mild lung injury, air leaked through the exhalation port to 618 and 812 mm when inspiratory pressure was increased from 10 to 18 cmH2O, respectively, with the expiratory pressure at 5 cm H2O.
 Tran K, (2012) Aerosol Generating Procedures and Risk of Transmission of Acute Respiratory Infections to Healthcare Workers: A Systematic Review. PloS one. 7: e35797 HFNC, NIV, BiPAP Systematic review; Ten non-randomized studies included (Five relevant case–control studies and five retrospective cohort studies) NIV was reported to present an increased risk of transmission of SARS to HCWs [n = 2 cohort; OR 3.1(1.4, 6.8)]. HFNC and manipulation of oxygen or BiPAP masks were not found to be significant in terms of risk to HCWs
Studies not directly related to COVID-19, testing various types of ventilatory support and interfaces: corroboration of safety
Gaeckle NT, (2020) Aerosol Generation from the Respiratory Tract with Various Modes of Oxygen Delivery. Am J Respir Crit Care Med. 202: 1115–1124 Non-humidified NC, face mask, heated and humidified HFNC, and NIPPV, in a negative pressure room Clinical study (N = 10). Aerosol generation was measured from healthy participants with each oxygen mode during maneuvers of normal breathing, talking, deep breathing, and coughing Oxygen delivery modalities of humidified HFNC and NIPPV did not increase aerosol generation from the respiratory tract
Studies not directly related to SARS-COV-2, with equivocal findings regarding risks
Agarwal A, (2020) High-flow nasal cannula for acute hypoxemic respiratory failure in patients with COVID-19: systematic reviews of effectiveness and its risks of aerosolization, dispersion, and infection transmission Can J Anaesth. 67(9):1217–1248 HFNC Systematic review; seven studies included (six simulation studies, one crossover study) Included studies did not provide data that can be extrapolated to the risk of airborne transmission of SARS-CoV-2
  1. HFNC high-flow nasal cannulae, NIV non-invasive ventilation, HVNI high velocity nasal insufflation, LFO2 low flow oxygen therapy, OM conventional oxygen mask, BiPAP bi-level positive airway pressure, NC  nasal cannula, NIPPV non-invasive positive pressure ventilation, NRB non-rebreather mask