EyeWorld Asia-Pacific March 2021 Issue

SECONDARY FEATURE EWAP MAR C H 2021 21 by Vaishali Vasavada, MS, and Samaresh Srivastava, DNB Airflow and aerosol management in the COVID era practice Contact information Vasavada: vaishali@raghudeepeyeclinic.com On 27 November 2020, the APACRS held a webinar in conjunction with the Bangladesh Society of Cataract & Refractive Surgeons (BSCRS) annual conference 2020 on “What’s New in Cataract & Refractive Surgery.” This article was written by the authors based on their presentation on “Airflow and aerosol management in the new COVID era practice for every cataract and refractive surgeon.” A s the COVID-19 infection continues to be a menace, there is a fear of transmission in ophthalmic outpatient (OPD) and operating room (OR) settings, due to close proximity of healthcare providers with patients. It is therefore important to understand the dynamics of exhaled airflow as well as circulating room air. We used the Schlieren imaging technique, 1-3 a noninvasive, optical imaging technique that helps to visualize the movement of air around us. This setup was used to analyze exhaled airflow patterns from patients attending OPD and OR (Figure1). The patient was made to sit (OPD) or lie down (OR) and the exhaled airflow studied during normal breathing, conversation, and Figure 1. Components of the Schlieren imaging setup: a. Parabolic mirror mounted on a table for the Schlieren imaging setup; b. a small LED light source covered with aluminium foil to create a pinhole. A razor blade with a thin edge is placed on sytrofoam to act as a light block for the reflected light; c and d. Schlieren imaging setup created for the study in the operating room and outpatient clinic respectively. coughing under the following conditions: without any mask, with an N95 mask, and a face shield held in front of the patient’s face. Testing was done with the metallic nose bridge strip of the mask loosely apposed over the patient’s nose, as well as by taping the upper border of the mask on to the patient’s nasal bridge. To evaluate the influence of a forced draft of air on the exhaled air, all these observations were recorded with the ceiling mounted air conditioning (AC) unit turned off versus on. We found that when the patient did not wear a mask, free flow of exhaled air was seen from the patient’s mouth and nose during breathing, talking, and coughing. Wearing the mask dampened the force and travelled distance of the exhaled airflow. If the upper edge of the mask was not well apposed around the nose, there was significant air leakage from the upper border of the mask (Figure 2, Figure 3). Taping the upper edge of the mask significantly dampened this leakage (Figure 2). With the AC turned off, there was free flow of exhaled air towards the surgeon. However, when the patient was made to sit or lie down so that they were under the direct draft of the ceiling mounted AC unit, the vertical air column dampened and dissipated the forward stream of exhaled airflow away from the surgeon (Figure 4). When the patient was made to hold a plastic sheet close to their face, this Vaishali VASAVADA, India Consultant Ophthalmologist Raghudeep Eye Hospital, Jaipur Samaresh Srivastava, India Consultant Ophthalmologist Raghudeep Eye Hospital, Jaipur