Background-oriented schlieren imaging during Jet ventilation models aersolization during COVID-19

ABSTRACT

Introduction: During the COVID-19 pandemic, minimizing the surgeon's exposure to aerosol-generating procedures is critical, and to our knowledge, the airflow dynamics and subsequent risk to the surgical team due to a back-flow or plume during jet ventilation has not been studied. Backgroundoriented Schlieren (BOS) imaging detects distortions in airflow to see the invisible a density gradient creates a refractive index change in the air, which uses small shifts to the recording of a visually textured background that are revealed using imaging-processing techniques. We aimed to use the BOS technique to illustrate the airflow patterns of jet ventilation. Method: A manikin model of jet ventilation was created to mimic lung compliance in an open system. A laryngoscope was used to expose the model and was suspended. The Monsoon III high-frequency jet ventilation system (Vyaire, Chicago, Illinois, USA) was used in either a supraglottic (delivered via laryngoscope port) or infraglottic technique (Hunsaker Mon-Jet ventilation theter, Medtronic, Minneapolis, USA). Various delivery settings were tested including driving pressure, ventilation frequency, and use of a variety of suction types/position. Images were obtained with a high-speed camera, and BOS processing was performed. Plume size was measured with ImageJ software (National Institutes of Health, Bethesda, Maryland, USA). Results: We successfully used BOS imaging to demonstrate variations in plume volume during supraglottic and infraglottic techniques. Low-frequency jet ventilation (12 cycles/min) and lower driving pressures had a smaller plume than highfrequency jet ventilation (120 cycles/min) or higher driving pressures with all other settings stable. There appeared to be a higher transnasal plume during supraglottic jet ventilation. Suction position significantly affected the plume size. Conclusion: High-frequency, low-volume, infraglottic jet ventilation with dual suction appears to have a lower risk of aerosolization compared with other modes of ventilation. Higher driving pressures were correlated to plume size.