Study models the airborne transmission of COVID-19 in a hospital outpatient examination room

A recent work posted to the Research Square* preprint server and under consideration at Scientific Reports assessed infection control strategies for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in hospital consultation rooms.

Study: Infection control for COVID-19 in hospital examination room. Image Credit: BlurryMe/Shutterstock
Study: Infection control for COVID-19 in hospital examination room. Image Credit: BlurryMe/Shutterstock

Background

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 is a serious concern for human health and the global economy. COVID-19 primarily spread through indirect and direct contact with respiratory droplets. Recently, airborne transmission of SARS-CoV-2 has also been reported. 

Healthcare professionals are at the front lines of SARS-CoV-2 patient care and have an increased risk for viral infection due to their close interaction with COVID-19 patients. Moreover, the safety of healthcare staff is critical to the healthcare system's long-term viability.

Despite the recommended infection control procedures for healthcare professionals, many have been infected during the ongoing COVID-19 pandemic, suggesting that the existing infection control techniques are ineffective. Furthermore, data regarding environmental variables' impact and proof-based approaches to lower SARS-CoV-2 infection risk in healthcare settings are lacking.

About the study

In the present work, the scientists modeled COVID-19 patients' exhalation of tiny and large aerosol particles in a hospital outpatient room for otolaryngologic examination, where medical processes need face mask removal. The study interrogated the impacts of environmental elements, aerosol suction equipment, and ventilation on SARS-CoV-2 spread via aerosols. The influence of coughing, humidity as a regulable environmental element, and suction apparatus as an efficient regulatory approach in COVID-19 transmission from patients to healthcare personnel were analyzed. 

The researchers established a virtual simulation of an otolaryngology consultation room in the outpatient setting at Chiba University Hospital, Japan, using Fusion 360, a three-dimensional (3D) computer-aided design software. The k–ω shear stress transport turbulence prototype was used to solve the 3D unsteady Reynolds-averaged Navier–Stokes equations. For this, the STAR-CCM+ software consisting of a second-order stratified flow solver centered on the semi-implicit strategy for pressure-related equations was used. The working fluid air at normal temperature (25°C) and pressure (1 atm) and relative humidity of 100% (RH100) and 75% (RH75) were analyzed.

Simulations were conducted in the presence and absence of suction apparatus near the COVID-19 patient. The suction apparatus was anticipated to be the size suited to the room, and its 3D structure was established by employing computer-aided technology. Aerosols and air were drawn to the suction port at the tip of a flexible arm at 6.71 m/s rates and vented from the exhaust outlet at the device's back at 5.66 m/s rates. A filter in the suction apparatus was expected to eliminate the aspirated aerosol. Simulations were also undertaken considering the suction device was positioned 35 cm from the patient's mouth and near their mouth to explore the influence of the suction device's position on aerosol removal.

Findings and discussions

The results demonstrated that aerosols expelled from a COVID-19 patient's nose or mouth in a consultation room, where removal of the face mask was necessary, were significantly influenced by the rooms' airflow. In addition, the chances of these aerosols' deposition on the medical practitioner and in other places in the room could not be overlooked.

The present findings were congruent with the authors' prior research on infection control strategies in healthcare settings. In addition, when aerosol movements were modeled under the premise that a patient coughed, the aerosol number deposited on the doctor was equivalent to that occurring from normal patient expiration, despite tiny aerosols diffused extensively across the room.

The present models revealed that the large aerosol particles' diameter was decreased within seconds at RH75, which is greater than that of New York City, USA, all year. This indicates the need for greater emphasis on regulating smaller aerosols to minimize airborne SARS-CoV-2 transmission. The number of deposited, excluded, and suspended particles at RH75 was less than RH100 since most particles evaporated in around seven seconds. This suggests that humidity had a remarkable impact on particle size. In addition, streamlines replaced particles with very low mass in this investigation.

A suction device may more efficiently remove aerosol dispersion during coughing and normal expiration than depending on the maximum airflow capacity in the rooms. The particle removal capacity of the suction apparatus was lower during coughing relative to normal exhalation.

Hence, more efficient infection control methods were required to combat more infectious illnesses and mutants that cause high rates of sneezing and coughing. Notably, positioning the vacuum inlet of the suction apparatus in a direction toward the mouth of the patient instead of space closer to the patient exhaling pathogenic aerosols was found to be critical.

Conclusions

The present theoretical study findings illustrated that a suction apparatus could reduce healthcare workers' aerosol exposure from COVID-19 patients by substantially removing both small and large aerosol particles. Nevertheless, the expulsion efficiency of coughing patients correlates inversely with particle size, and humidity has a significant impact on aerosol behavior, emphasizing the necessity for interventions against smaller aerosols.

Altogether, the study points to the benefits and drawbacks of deploying a suction device to safeguard against COVID-19 and potential respiratory infections in the future. The comprehensive risk estimation approach employed in the study could be flexibly adopted into clinical practice for effective infection control against respiratory illnesses, including SARS-CoV-2.

*Important notice

Research Square publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
Shanet Susan Alex

Written by

Shanet Susan Alex

Shanet Susan Alex, a medical writer, based in Kerala, India, is a Doctor of Pharmacy graduate from Kerala University of Health Sciences. Her academic background is in clinical pharmacy and research, and she is passionate about medical writing. Shanet has published papers in the International Journal of Medical Science and Current Research (IJMSCR), the International Journal of Pharmacy (IJP), and the International Journal of Medical Science and Applied Research (IJMSAR). Apart from work, she enjoys listening to music and watching movies.

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