Development and efficacy testing of a portable negative pressure enclosure for airborne infection containment.

OBJECTIVES: To overcome the shortage of personal protective equipment and airborne infection isolation rooms (AIIRs) in the COVID-19 pandemic, a collaborative team of research engineers and clinical physicians worked to build a novel negative pressure environment in the hopes of improving healthcare worker and patient safety. The team then sought to test the device's efficacy in generating and maintaining negative pressure. The goal proved prescient as the US Food and Drug Administration (FDA) later recommended that all barrier devices use negative pressure. METHODS: Initially, engineers observed simulations of various aerosol- and droplet-generating procedures using hospital beds and stretchers to determine the optimal working dimensions of the containment device. Several prototypes were made based on these dimensions which were combined with filters and various flow-generating devices. Then, the airflow generated and the pressure differential within the device during simulated patient care were measured, specifically assessing its ability to create a negative pressure environment consistent with standards published by the Centers for Disease Control and Prevention (CDC). RESULTS: The portable fans were unable to generate any airflow and were dropped from further testing. The vacuums tested were all able to generate a negative pressure environment with the magnitude of pressure differential increasing with the vacuum horsepower. Only the 3.5-horsepower Shop-Vac, however, generated a -3.0 pascal (Pa) pressure gradient, exceeding the CDC-recommended minimum of -2.5 Pa for AIIRs. CONCLUSION: A collaborative team of physicians and engineers demonstrated the efficacy of a prototype portable negative pressure environment, surpassing the negative pressure differential recommended by the CDC.

Design and in-vitro testing of a portable patient isolation chamber for bedside aerosol containment and filtration.

The emergence of the SARS-CoV-2 pandemic has imposed a multitude of complications on healthcare facilities. Healthcare professionals had to develop creative solutions to deal with resource shortages and isolation spaces when caring for COVID positive patients. Among many other solutions, facilities have utilized engineering strategies to mitigate the spread of viral contamination within the hospital environment. One of the standard solutions has been the use of whole room negative pressurization (WRNP) to turn a general patient room into an infection isolation space. However, this has not always been easy due to many limitations, such as direct access to the outdoors and the availability of WRNP units. In operating rooms where a patient is likely to go through aerosol-generating procedures, other solutions must be considered because most operating rooms use positive pressure ventilation to maintain sterility. The research team has designed, built, and tested a Covering for Operations during Viral Emergency Response (COVER), a low-cost, portable isolation chamber that fits over a patient's torso on a hospital bed to contain and remove the pathogenic agents at the source (i.e., patient's mouth and nose). This study tests the performance of the COVER system under various design and performance scenarios using particle tracing techniques and compares its efficiency with WRNP units. The results show that COVER can dramatically reduce the concentration of particles within the room, while WRNP is only effective in preventing the room-induced particles from migrating to adjacent spaces.

Three-dimensional analysis of the effect of human movement on indoor airflow patterns.

Human activity is known to leave significant effects on indoor airflow patterns. These patterns are carefully designed for many facilities such as cleanrooms, pharmaceutical settings, and healthcare environments, where human-induced wakes contribute to the transport of contaminants. Therefore, the knowledge about these wakes as it relates to indoor air quality is critical. As a result, a series of experiments were conducted in a controlled chamber to study the three-dimensional effects of true human walking on airflow. Experiments were designed to capture the effect of human walking under three different flow conditions, and for two different walking schemes. The results show that the effect of walking on the airflow is not negligible and can sustain up to 10 seconds after the moving body has passed. Walking on a straight line creates significant change in the velocity normal to the walking path and vertical to the plane of walking movement. These changes were detectable till 1.0 m away from the walking track. Also, the similarity between airflow patterns of walking once and twice illustrated a promising opportunity of predicting the flow patterns of random walk from a set of base cases.

COVID-19 Outbreak and Hospital Air Quality: A Systematic Review of Evidence on Air Filtration and Recirculation.

The outbreak of SARS-CoV-2 has made us all think critically about hospital indoor air quality and the approaches to remove, dilute, and disinfect pathogenic organisms from the hospital environment. While specific aspects of the coronavirus infectivity, spread, and routes of transmission are still under rigorous investigation, it seems that a recollection of knowledge from the literature can provide useful lessons to cope with this new situation. As a result, a systematic literature review was conducted on the safety of air filtration and air recirculation in healthcare premises. This review targeted a wide range of evidence from codes and regulations, to peer-reviewed publications, and best practice standards. The literature search resulted in 394 publications, of which 109 documents were included in the final review. Overall, even though solid evidence to support current practice is very scarce, proper filtration remains one important approach to maintain the cleanliness of indoor air in hospitals. Given the rather large physical footprint of the filtration system, a range of short-term and long-term solutions from the literature are collected. Nonetheless, there is a need for a rigorous and feasible line of research in the area of air filtration and recirculation in healthcare facilities. Such efforts can enhance the performance of healthcare facilities under normal conditions or during a pandemic. Past innovations can be adopted for the new outbreak at low-to-minimal cost.

Performance analysis of portable HEPA filters and temporary plastic anterooms on the spread of surrogate coronavirus.

The outbreak of COVID-19, and its current resurgence in the United States has resulted in a shortage of isolation rooms within many U.S. hospitals admitting COVID-19-positive cases. As a result, hospital systems, especially those at an epicenter of this outbreak, have initiated task forces to identify and implement various approaches to increase their isolation capacities. This paper describes an innovative temporary anteroom in addition to a portable air purifier unit to turn a general patient room into an isolation space. Using an aerosolization system with a surrogate oil-based substance, we evaluated the effectiveness of the temporary plastic anteroom and the portable air purifier unit. Moreover, the optimal location of the portable unit, as well as the effect of negative pressurization and door opening on the containment of surrogate aerosols were assessed. Results suggested that the temporary anteroom alone could prevent the migration of nearly 98% of the surrogate aerosols into the adjacent corridor. Also, it was shown that the best location of a single portable air purifier unit is inside the isolation room and near the patient's bed. The outcome of this paper can be widely used by hospital facilities managers when attempting to retrofit a general patient room into an airborne infection isolation room.

Renovation in Hospitals: Pressurization Strategies by Healthcare Contractors in the United States.

OBJECTIVE: The objective of the study was to identify current practices utilized by contractors in healthcare renovation projects. BACKGROUND: Renovation in healthcare facilities comprises nearly half of all healthcare construction. Since a complete shutdown of the healthcare facility during renovation is typically not feasible, efforts must be taken to isolate ongoing functions of the hospital from activities in the construction zone. There are numerous documented cases of morbidity and mortality related to construction activities in the hospital. Hence, guidelines recommend negative pressurization of the construction zone to prevent the migration of dust and potential pathogenic agents into the functioning zone. METHOD: To accomplish the paper objective, a questionnaire was developed to address pressurization strategies, the use of backup systems and anterooms, and workforce training for healthcare projects. One hundred twenty-nine project managers and superintendents from top healthcare construction companies in the United States participated in the study. RESULTS: Results show that owners influence pressurization strategy, but contractors typically assume a primary role in establishing pressurization levels, monitoring conformance, and training construction personnel. However, without solid evidence of effectiveness, pressurization levels often vary from Center for Disease Control standards. CONCLUSION: Further research is needed to establish evidence-based practices and to develop training modules for construction crews to support these best practices. Promoting evidence-based training can improve patient safety and minimize adverse patient outcomes.

Renovation in hospitals: Training construction crews to work in health care facilities.

BACKGROUND: Health care facilities require frequent renovations to maintain or enhance their service, and to meet the dynamic demands of their patients. Construction activities in active health care facilities are a significant contributor to various challenges that range from infection to death. It is therefore essential to minimize the adverse impacts of construction activities on health care units as well as their adjacent sites. METHODS: A questionnaire was developed to study current training modules to prepare construction crews to work in health care environments. The survey was disseminated among professionals of the top 15 health care contractors. A total of 129 individuals participated, and their responses were analyzed using descriptive and categorical statistics. RESULTS: This study investigates current training practices regarding (1) the level of training, (2) the frequency of training, and (3) the impact that the sensitivity of the project has on the training. To effectively prepare construction crews, special training must be provided to them. CONCLUSIONS: There are uncertainties about the sufficiency and impact of the existing training. Existing trainings are tailored for upper management positions, and the amount/frequency of training for construction crews are substantially low. Findings of this study contribute to characterizing the activities and conditions pertaining to training of construction crews.

Ventilation Rates and Airflow Pathways in Patient Rooms: A Case Study of Bioaerosol Containment and Removal.

Most studies on the transmission of infectious airborne disease have focused on patient room air changes per hour (ACH) and how ACH provides pathogen dilution and removal. The logical but mostly unproven premise is that greater air change rates reduce the concentration of infectious particles and thus, the probability of airborne disease transmission. Recently, a growing body of research suggests pathways between pathogenic source (patient) and control (exhaust) may be the dominant environmental factor. While increases in airborne disease transmission have been associated with ventilation rates below 2 ACH, comparatively less data are available to quantify the benefits of higher air change rates in clinical spaces. As a result, a series of tests were conducted in an actual hospital to observe the containment and removal of respirable aerosols (0.5-10 µm) with respect to ventilation rate and directional airflow in a general patient room, and, an airborne infectious isolation room. Higher ventilation rates were not found to be proportionately effective in reducing aerosol concentrations. Specifically, increasing mechanical ventilation from 2.5 to 5.5 ACH reduced aerosol concentrations only 30% on average. However, particle concentrations were more than 40% higher in pathways between the source and exhaust as was the suspension and migration of larger particles (3-10 µm) throughout the patient room(s). Computational analyses were used to validate the experimental results, and, to further quantify the effect of ventilation rate on exhaust and deposition removal in patient rooms as well as other particle transport phenomena.

Directional Airflow and Ventilation in Hospitals: A Case Study of Secondary Airborne Infection.

Since the 1990s, improvements in ventilation techniques and isolation procedures have been widely credited with the decline in nosocomial transmission of tuberculosis and other airborne diseases. Little effort, however, has been made to study the risk of isolation patients acquiring secondary infections from contaminated air migrating into negatively pressurized isolation rooms from adjacent spaces. As a result, an actual hospital was used to observe the transport of aerosol from a nursing station and general patient room to a nearby airborne infectious isolation room (AIIR). Aerosols ≤3.0 µm (viruses and most airborne bacteria) were found to be capable of migrating 14.5m from a general patient room to an AIIR anteroom entrance in <14 minutes at concentrations 2-5 times greater than ambient (e.g. background). Concentrations of aerosols within the anteroom and isolation room, however, remained virtually unchanged from ambient levels, indicating the effectiveness of door position and (or) ventilation. In contrast, gravitational settling and surface deposition appeared to limit the migration of aerosols >3.0 µm to the entrance of the general patient room (4.5m).