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

Abstract

Objective All respiratory care represents some risk of becoming an aerosol‐generating procedure (AGP) during COVID‐19 patient management. Personal protective equipment (PPE) and environmental control/engineering is advised. High velocity nasal insufflation (HVNI) and high flow nasal cannula (HFNC) deliver high flow oxygen (HFO) therapy, established as a competent means of supporting oxygenation for acute respiratory distress patients, including that precipitated by COVID‐19. Although unlikely to present a disproportionate particle dispersal risk, AGP from HFO continues to be a concern. Previously, we published a preliminary model. Here, we present a subsequent highresolution simulation (higher complexity/reliability) to provide a more accurate and precise particle characterization on the effect of surgical masks on patients during HVNI, low‐flow oxygen therapy (LFO2), and tidal breathing. Methods This in silico modeling study of HVNI, LFO2, and tidal breathing presents ANSYS fluent computational fluid dynamics simulations that evaluate the effect of Type I surgical mask use over patient face on particle/droplet behavior. Results This in silico modeling simulation study of HVNI (40 L min−1) with a simulated surgical mask suggests 88.8% capture of exhaled particulate mass in the mask, compared to 77.4% in LFO2 (6 L min−1) capture, with particle distribution escaping to the room (> 1 m from face) lower for HVNI+Mask versus LFO2+Mask (8.23% vs 17.2%). The overwhelming proportion of particulate escape was associated with mask‐fit designed model gaps. Particle dispersion was associated with lower velocity. Conclusions These simulations suggest employing a surgical mask over the HVNI interface may be useful in reduction of particulate mass distribution associated with AGPs.

The 2019–2020 novel coronavirus (severe acute respiratory syndrome coronavirus 2) pandemic: A joint american college of academic international medicine-world academic council of emergency medicine multidisciplinary COVID-19 working group consensus paper

“…HFNC use with a surgical mask placed over it may decrease the risk. [ 198 ] During all airway and respiratory maneuvers, extreme caution should be exercised, and the patient should be closely monitored for factors that would indicate a need for intubation, including decreasing or increasing respiratory rate, depressed mental status, worsening hypoxia despite escalating therapy, and inability to protect the airway. [ 190 ] During these advanced procedures, it is important to maintain the safety of HCWs by limiting the number of those directly caring for the patient to essential personnel and utilizing a negative pressure room (if available).…”

Assessment of effectiveness of optimum physical distancing phenomena for COVID-19

“…Leonard et al 26 examined how the spread of COVID-19 can be mitigated through nasal inhalation with a surgical mask. The use of surgical masks has been recommended by numerous health care professionals to slow down the spread of the virus.…”

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

“…The study was limited by the small population and questionable methodology, and further emphasized the current lack of systematic appraisal of airborne viral transmission from infected patients. Finally, an in silico computational fluid dynamics simulation by Leonard et al showed that using a simple surgical mask over the HFNC interface is effective in reducing distribution of aerosolized particles [13].…”