Ventilation strategies based on an aerodynamic analysis during a large-scale SARS-CoV-2 outbreak in an acute-care hospital

Interventions used to reduce infectious aerosol concentrations in hospitals-a review

Background

The COVID-19 pandemic highlighted the need for improved infectious aerosol concentrations through interventions that reduce the transmission of airborne infections. The aims of this review were to map the existing literature on interventions used to improve infectious aerosol concentrations in hospitals and understand challenges in their implementation.

Methods

We reviewed peer-reviewed articles identified on three databases, MEDLINE, Web of Science, and the Cochrane Library from inception to July 2024. 6417 articles were identified, 160 were reviewed and 18 were included.

Findings

Results on aerosol concentration were discussed in terms of three categories: (1) filtration and inactivation of aerosol particles; (2) effect of airflow and ventilation on aerosol concentrations; and (3) improvements or reduction in health conditions. The most common device or method that was outlined by researchers was high efficiency particulate air (HEPA) filters which were able to reduce aerosol concentrations under investigation across the included literature. Some articles were able to demonstrate the effectiveness of interventions in terms of improving health outcomes for patients.

Interpretation

The key finding is that infectious aerosol concentration improvement measures based on filtration, inactivation, improved air flow dynamics, and ventilation reduce the likelihood of nosocomial infections. However limitations of such approaches must be considered such as noise pollution and effects on ambient humidity. Whilst these efforts can contribute to improved air quality in hospitals, they should be considered with the other interacting factors such as microclimates, room dimensions and use of chemical products that effect air quality.

Funding

This study is funded by the National Institute for Health and Care Research (NIHR) (NIHR205439).

Nosocomial Coronavirus Disease 2019 during 2020-2021: Role of Architecture and Ventilation

Nosocomial coronavirus disease 2019 (COVID-19) is a major airborne health threat for inpatients. Architecture and ventilation are key elements to prevent nosocomial COVID-19 (NC), but real-life data are challenging to collect. We aimed to retrospectively assess the impact of the type of ventilation and the ratio of single/double rooms on the risk of NC (acquisition of COVID-19 at least 48 h after admission). This study was conducted in a tertiary hospital composed of two main structures (one historical and one modern), which were the sites of acquisition of NC: historical (H) (natural ventilation, 53% single rooms) or modern (M) hospital (double-flow mechanical ventilation, 91% single rooms). During the study period (1 October 2020 to 31 May 2021), 1020 patients presented with COVID-19, with 150 (14.7%) of them being NC (median delay of acquisition, 12 days). As compared with non-nosocomial cases, the patients with NC were older (79 years vs. 72 years; p < 0.001) and exhibited higher mortality risk (32.7% vs. 14.1%; p < 0.001). Among the 150 NC cases, 99.3% were diagnosed in H, mainly in four medical departments. A total of 73 cases were diagnosed in single rooms versus 77 in double rooms, including 26 secondary cases. Measured air changes per hour were lower in H than in M. We hypothesized that in H, SARS-CoV-2 transmission was favored by short-range transmission within a high ratio of double rooms, but also during clusters, via far-afield transmission through virus-laden aerosols favored by low air changes per hour. A better knowledge of the mechanism of airborne risk in healthcare establishments should lead to the implementation of corrective measures when necessary. People's health is improved using not only personal but also collective protective equipment, i.e., ventilation and architecture, thereby reinforcing the need to change institutional and professional practices.