Building Airborne Isolation Units During Emergent Times

What would a hospital do if there was an influx of infectious patients who required airborne isolation? Such patients require negative pressure hospital rooms, which is extremely taxing on the healthcare system because most hospitals only have a handful of these rooms per unit. Diseases like SARS, MERS, highly-pathogenic avian influenza, measles, and Ebola, all require airborne isolation precautions and represent the full spectrum of biological threats and events we have seen in the past 15 years. Despite the increasing need for such rooms, most hospitals are not equipped to handle high volumes of patients requiring them. Hospital ventilation systems are designed and engineered to handle a handful of these rooms per unit, and so response plans often include moving these patients to designated areas like gymnasiums or tented-care areas built in parking lots.

A research team, led by University of Colorado at Boulder professor, Shelly Miller, PhD, sought to change this deficiency. Their work focused on designing and implementing a negative-pressure isolation ward to handle a surge of airborne infectious patients, like would be seen in an outbreak of the diseases mentioned above. The team tested their design in a functioning hospital unit in the San Francisco Bay Area in Northern California.

The temporary negative pressure ward was built within a unit that had its own dedicated air handling unit (AHU), dedicated bathroom exhaust systems, a firewall separating the unit from the rest of the hospital, and a separate dedicated exhaust system for return registers in existing isolation rooms (ISRs). Two heating, ventilation, air conditioning (HEPA)-filtered negative-air machines were used to establish the negative pressure, as well as a temporary anteroom and plastic sheeting (with zippered openings for doors, taped to the walls), ceiling frame, and floors to ensure the space was properly sealed.

Dr. Miller’s team performed pressure measurements throughout the experiment to ensure negative pressure was maintained. During these measurements, they found that there was positive pressure being generated in the adjacent stairwell, which was effective against letting airborne microbes into the area, unless the doors were opened. To combat this, the team utilized germicidal UV lamps and installed them near the door at each stairwell internal to the isolation unit. Despite these stairwells, the main entrance and exit into the unit was through the anteroom.

Following their analysis, the team found that they were able to maintain negative pressure that was actually higher than the CDC recommendations for airborne isolation and there was no pressure reversal during the entering and exiting of the ward by medical staff. They did find that “pressures within the ward changed, with some rooms becoming neutrally or slightly positively pressured”, which means that healthcare staff would need to wear proper personal protective equipment (PPE) at all times in the unit and not just while in the patient rooms.

Overall, their work revealed that it is possible to create a temporary negative pressure isolation unit within a hospital as a means of responding to an influx of airborne infectious disease patients.

I was fortunate to have the opportunity to chat with Dr. Miller about this study and some of the implications for hospital response and infection control practices. She noted that hospital administration was very supportive of the project and that it took additional time to get all the necessary hospital stakeholders on board and informed. The nursing staff were especially interested and engaged during the experiment. It really does take a village! She stated that the infection prevention and control team was heavily involved and present at every meeting.

I asked Dr. Miller if she considered using solid barriers instead of the plastic sheeting, of which she noted that their goal was to make this as cheap and easy as possible. She pointed out that although major hospitals have the capabilities to respond to an influx of airborne infectious disease patients, she worries about the smaller, rural hospitals. This research could provide them with a temporary response measure.

From an infection preventionist standpoint, I found it interesting that they did not require staff to wear PPE while testing the temporary unit. I believe that future research work should include this component as it is very taxing on staff to wear the respiratory protection required for airborne isolations, for prolonged periods of time. Although most infection prevention programs dealt with the possibility of establishing additional negative pressure areas and rooms during the 2014/2015 Ebola outbreak, Dr. Miller’s work provides us with less costly methods to handle patients that require airborne isolation, but perhaps not such enhanced isolation precautions.