Effectiveness of surgical masks in decreasing aerosolization in patients on supplemental oxygen

ABSTRACT

INTRODUCTION: Caring for patients with acute hypoxic respiratory failure from COVID-19 has been quite difficult for healthcare workers for a variety of reasons. For the last several months patients have been encouraged or required to wear surgical masks due to evolving best practice but concern among healthcare providers remains elevated to this day, specifically regarding how much protection a surgical mask actually offers when the patient is on supplemental oxygen. We performed high-fidelity analysis using laseraugmented detection of exhalations to quantify mitigation of aerosols and droplets by surgical masks worn by patients over the oxygen delivery device. Due to the inherent significant population variability suffering from COVID-19, the already burdensome requirements on an increasingly fatigued staff, difficulty in repeatability, and the sometimes marked differences in patient rooms, we chose a manikin respiration system to allow us to visualize and quantify the direction and density of exhalations on supplemental oxygen under reproducible conditions. METHODS: The “healthy” manikin had a set respiratory rate and tidal volume of 12 breaths per minute and 500 mL, while the “COVID” manikin was set at 20bpm and 350 mL. The exhalations were visualized using an aerosol fog composed of approximately 1-5 micron water-based droplets. (Image 1). RESULTS: We found that while wearing nasal cannula without a mask, exhalations have concentrated linear momentum for >0.5m from mouth and may be directly in the direction of a healthcare worker. The addition of a simple surgical mask decreased the concentrated linear momentum by half (0.26m) and redirected the exhalated gas laterally and inferiorly. There were similar findings while wearing simple oxygen facemask with and without surgical mask. CONCLUSIONS: Wearing a surgical mask significantly reduces momentum of the initial exhalation and redirects the exhalation puffs away from providers. We demonstrate this simple strategy provides additional protection for healthcare providers and first responders treating patients with COVID-19 and other contagious disease spread through infectious aerosols and droplets.