At a time when resources are running low…budgets, space, PPE and other equipment…be sure to remember the biggest tool you have at your disposal: your building.
We heard about one Skilled Nursing Facility (SNF) facility in Lancaster, Pennsylvania, who put their building to work for them. They used their HVAC system to effectively create a negative pressure isolation unit for COVID-19 (SARS-CoV-2) patients.
Since COVID-19 is primarily transmitted via airborne particles, the primary need was to isolate airborne virus particles so they couldn’t escape the “containment unit” (aka, the wing of the facility that they had designated for COVID-19 patients).
This need for isolation over extended periods of time has made it incredibly difficult for facilities to safely accommodate a potential surge of COVID-19 patients while keeping other staff and residents safe. However, this facility may have found a temporary, budget-friendly solution to meet the needs of the current pandemic.
This study was conducted at a 114-bed Skilled Nursing Facility (SNF) in Lancaster, Pa., that also shared a building and campus with residential and personal care units. The negative pressure and containment measures were applied to one hallway on the bottom floor of the SNF that had previously been a short-term rehabilitation area. A series of fire doors separated the hallway from the rest of the building.
This study required quick, simple modifications to the affected ward (hallway) of the SNF. Continuous pressure differential measurements and modeling were used to ensure that negative pressure was maintained and airborne particles were contained.
HVAC modifications were begun on April 2, 20200, and completed on April 6 (only 4 days later). The modifications included:
- Adding two new 0.43 m3/s (920 CFM) blowers within the Energy Recovery Ventilator (ERV) to enhance the normal exhaust pattern.
- Turning off the incoming outdoor ventilation fan.
- Mounting 0.51-m 2.12 m3/s (4500 CFM) exhaust fan to the outside of the relative outdoor intake grate to reverse air flow and convert the hall to 100% exhaust.
- Removing the preconditioning unit of the ERV.
- Closing the fire damper located above the fire door to increase the exhausting of air within the hall.
- Replacing HEPA (High-Efficiency Particulate Air) filters with MERV 8 filters.
- Restricting access within 15.2 meters around the exterior exhaust vent.
In addition to the HVAC modifications, two sets of 3-sheet plastic barriers were installed at the front of the hallway to create a temporary anteroom. The plastic barriers were made of three overlapping sections of 6 ml plastic that was attached to the walls and ceiling using wood lathe. The anteroom contained a HEPA purifier fitted with 0.1-meter ductwork to exhaust air into the hallway and toward the isolation wing. This created a series of negative pressure zones between the isolation space, anteroom and the rest of the SNF.
At the end of the isolation wing, a stairwell acted as a second anteroom specifically for the admission and discharge of residents. This anteroom was needed to prevent residents from being transported through other areas of the facility and potentially exposing residents and staff. The design of the stairwell allowed the use of two separate doors (one door to the outside and one to the hall) to create the isolation space. This allowed patients and visitors to be admitted through the stairwell anteroom entrance directly to the negative pressure space and minimized possible SARS-CoV-2 exposure to the rest of the facility.
Housekeeping staff was kept out of the isolation unit and the nursing staff within the unit were instead responsible for housekeeping tasks. All housekeeping materials were designated to the isolation wing and were not transported outside of the negative isolation space once delivered to the anteroom. Waste and laundry were both double-bagged and removed via the stairwell anteroom daily. Donning and doffing of nursing personal protective equipment (PPE) was done just outside the anteroom on the isolation side so that PPE could be cleaned and reused.
Air Pressure Differential Measurements:
Continuous measurement of pressure differentials was conducted from May 14, 2020 to May 21, 2020. Measurements were taken at two locations outside the hallway anteroom (one outside the isolation space, and one inside).
A second set of pressure differential measurements were conducted in the form of periodic spot-checks, measuring differentials between the anteroom and a location outside the building.
A third set of measurements were recorded from May 23, 2020 through May 25, 2020 to measure differentials between the nursing station outside the isolation space and outside the building.
Personal Protective Equipment (PPE):
Staff were required to wear PPE throughout the isolation unit, including gowns, goggles N95 masks and gloves.
The SNF was we able to maintain continuous negative pressure within the isolation unit for a documented period of 14 days. Air pressure differential measurements showed that the isolation space maintained an average hourly value of -2.3 Pa pressure differential between it and the external hallway connected to the rest of the facility. Furthermore, all median pressure differentials were negative, which implies that the isolation space was at a lower pressure than the anteroom. This differential would have prevented any air flow out of the isolation space towards the anteroom and rest of the facility.
Negative pressure was also confirmed anecdotally: on-site observations were that the anteroom plastic sheet entryway remained continuously curved inward toward the isolation space, which indicates that pressure was negative on the isolation unit side compared to the rest of the facility.
Modeling of airborne particle movement within this isolation unit showed that particles can spread throughout the isolation space—from patient rooms to hallways, and vice versa—especially when patient doors are left open. This underlines the need for PPE and other protective measures within the isolation unit to prevent viral transmission to healthcare workers.
The SNF received its first known positive COVID-19 patient as a hospital transfer on April 8, 2020. From that date onward, and over the course of this study, the SNF did not acquire any new positive COVID-19 results within its own population of residents. Additionally, none of the healthcare workers assigned to work within the isolation space tested positive for the virus or presented with symptoms from then on. The isolation space was successfully implemented and, as of writing (Oct 3, 2020), continued to operate through the pandemic.
As of June 23, 2020, the isolation unit had consistently maintained a population of COVID-19 residents ranging from between 2 and 6 individuals. As of June 23rd, 14 confirmed COVID-19 residents had been treated in this negative isolation space, and the facility had utilized the isolation unit for a total of 21 individuals. Residents have been routinely treated and discharged from the isolation unit after negative test results are acquired (two negative tests within 48 hours).
Reinforcing Patient Care:
Residents of SNF often require high levels of care, which can be disrupted if the patient is transferred to a hospital or emergency facility. The isolation space created in this study allowed the SNF to maintain a high level of care for senior citizens of the SNF while protecting other residents. The creation of this negative pressure isolation units within a SNF (like this one) could help alleviate hospital admissions and staffing shortages, and help generate surge capacity without jeopardizing healthcare standards.
The creation and operation of this isolation unit required the involvement of professionals from many backgrounds, including administrators, medical directors, infection prevention teams, nursing staff, maintenance personnel, engineers, and respiratory therapists, among others. While this group of professionals is certainly varied, these are all professionals that nursing facilities and hospitals have relatively easy access to.
Traditional Infection Control Strategies:
This exercise used the same basic principles as a containment unit that we’d typically see during construction — except that instead of containing dust, they were focused on containing virus particles, too. It’s also important to note that instead of using portable negative air machines (like we’d typically see in construction), the facility made modifications to their HVAC system setup.
Applications in Other Facilities:
Many hospitals and nursing facilities are designed similarly to the facility described in this study: a main facility with branching off corridors that are fitted with corresponding HVAC systems. In facilities with similar setups, a temporary negative pressure unit like this one could hypothetically be set up to contain airborne virus particles at the levels recommended by CDC guidelines.
The best news is that these modifications are typically not very resource intensive and can be implemented rather quickly with the right expertise. While this isn’t a long-term solution, it is a quick and effective short-term solution to consider should needs become dire in the coming weeks.
Modifications to an existing HVAC system in a SNF resulted in a negative pressure isolation unit for residents with confirmed cases of COVID-19. The modifications were able to sustain negative pressures that met or exceeded CDC guidelines. The living community was able to offer expanded health services to residents and avoid transfers to emergency facilities, while preventing facility-based spread of the virus.
However, this study is just the start. While this example of retrofitting existing HVAC systems is certainly an option for meeting an influx of patient needs, attention should be paid to incorporating flexible air handling equipment in new and renovated facilities so that facilities can be more easily adapted in outbreak situations.
As president and chief executive officer, Dan focuses on the overall direction of the firm, strategic alliances, and business development, while upholding his commitment to clients to ensure their projects’ success. He remains involved in the field, applying his 30 years of experience to resolve the most complicated and high risk environmental hygiene issues encountered in healthcare facilities.