Summary: Preliminary Findings on Control of Dispersion of Aerosols and Droplets During High-Velocity Nasal Insufflation Therapy Using a Simple Surgical Mask: Implications for the High-Flow Nasal Cannula.

Topic: Aerosol Dispersion

Leonard S, Atwood CW Jr, Walsh BK, DeBellis RJ, Dungan GC, Strasser W, Whittle JS. Preliminary findings of control of dispersion of aerosols and droplets during high velocity nasal insufflation therapy using a simple surgical mask: implications for high flow nasal cannula, CHEST, 2020; 158:1046–9. https://doi.org/10.1016/j.chest.2020.03.043 

Leonard and colleagues conducted a high-resolution simulation to provide a more accurate and precise particle characterization on the effect of surgical masks on patients during high velocity nasal insufflation (HVNI), low‐flow oxygen therapy (LFO2), and tidal breathing. The CHEST 2020 article describes the authors’ preliminary results of computational fluid dynamics modeling (CFD) to evaluate the scale of potential environmental contamination associated with aerosol generation during HVNI. This silico modeling simulation study of HVNI at 40 LPM with a simulated surgical mask suggests 88.8% capture of exhaled particulate mass in the mask, compared to 77.4% in LFO2 at 6 LPM 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. 

In the study, the authors found that in this simulation a surgical mask modeled as applied over the HVNI cannula interface, maintained therapy efficacy while effectively containing the dispersal of potentially infectious particles. The researchers found that using HVNI as a means of high flow oxygen delivery presents a low risk of transmission compared to other ventilatory support devices. These simulations suggest employing a surgical mask over the HVNI interface may be useful in reduction of particulate mass distribution associated with AGPs, however, all scenarios (HVNI, LFO2, tidal breathing) resulted in particulate and airflow escape, and personal protective equipment/environmental precautions must be considered when treating patients receiving HVNI, even with the surgical mask. 

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CAUTION: US Federal law restricts this device to sale by or on the order of a physician. Indications, contraindications, warnings, and instructions for use can be found in the product labelling supplied with each device or at https://vapotherm.com/resources/support/precision-flow-reference/. For spontaneously breathing patients. High Velocity Therapy (HVT) does not provide total ventilatory requirements of the patient. It is not a ventilator. Decisions surrounding patient care depend on the physician’s professional judgment in consideration of all available information for the individual case, including escalation of care depending on patient condition.