Ultimately, employing a high-flow nasal cannula (HFNC) reduces the intubation rate among patients with severe hypoxemia. Furthermore, flush-rate NRM exhibits the same efficacy as a bag-valve-mask (BVM) device, becoming widely used for preoxygenation before intubation 16, 17. NCO combined with NRM at 15 L/min can reduce hypoxemia incidence before and during intubation 14, 15. More severe hypoxemia requires invasive mechanical ventilation, and preoxygenation is considered an adjunct of O 2 supplementation before emergent intubation. Besides conventional O 2 therapy, a higher flow rate of NCO (6–15 L/min) can increase FiO 2 from 0.49 to 0.72 13. Conventional non-invasive oxygen supplementation therapies usually involve low flow rates of < 15 L/min, including nasal cannula oxygenation (NCO 1–6 L/min), simple mask (5–10 L/min), and non-rebreathing mask (NRM 10–15 L/min), to provide a fraction of the inspired O 2 (FiO 2 0.24–0.66) 11, 12. Hypoxia is a symptom of severe COVID-19 9 for which supplemental oxygen is often administered using multiple devices 10. Several hospital procedures involving airways may discharge contaminated aerosols (aerosol-generating procedures, AGPs) 6, including nasogastric tube insertion, oxygenation therapy, noninvasive ventilation, mechanical ventilation, and tracheal intubation 7, 8. SARS-CoV-2 can survive in the aerosol form for ≥ 3 h 5. The discharge particle size ranges from droplets to aerosols, and the number of virions in the particle increases with particle size 4. Particularly the continual air flow generated by the airway during breathing can widely distribute the discharges 3. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted via upper-airway discharges, such as sneezing, coughing, or breathing 1, 2. Healthcare workers should be alert even at the foot side of the patient while administering oxygenation therapy. In the upright position, the foot area exhibited the highest aerosol concentration regardless of the oxygenation device than the head–trunk areas of the mannequin. For flow rates of < 15 L/min, oxygenation devices with mask-like effects, such as NRM or NCO with NRM, decreased aerosol dispersion more effectively than NCO alone or a simple mask. HFNC and flush-rate NRM yielded the longest dispersion distance and highest aerosol concentrations over the three sites of the mannequin than the other oxygenation devices and should use with caution. Two-dimension of the dispersion distance and the aerosol concentrations were measured at head, trunk, and foot around the mannequin for over 10 min. A simulated mannequin was designed to breathe at a minute ventilation of 20 L/min and used the following oxygen-therapy devices: nasal cannula oxygenation (NCO) at 4 and 15 L/min, nonrebreathing mask (NRM) at 15 L/min, simple mask at 6 L/min, combination of NCO at 15 L/min and NRM at 15 L/min, high-flow nasal cannula (HFNC) at 50 L/min, and flush rate NRM. This study evaluated the aerosol exposure risks while using common noninvasive oxygenation devices.
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