April 11, 2020

UNM researchers devise process for decontaminating PPE

A team of researchers at UNM established a set of protocols for decontaminating personal protective equipment that would be, under normal circumstances, disposable. The team, led by the UNM Center for Global Health director Douglas Perkins, will publish their findings on the preprint server for health sciences, MedRxiv.

Perkins told NM Political Report supply chain issues make securing protective gear a frequent problem at the pediatric ward of a rural government hospital in Kenya that he helps run.

“Under nearly all circumstances, we are challenged with supply chain management,” Perkins said. “Over the past 18 years, we have had to become very creative and come up with decontamination methods. Throwing some of this stuff away, there may not be more coming, so we have tended to recycle as much as we can in a safe way.”

Perkins said he and his team at UNM began developing a process for decontaminating PPE in New Mexico earlier this year, when he realized shortages could potentially hit the U.S.

“Several months ago, we ordered PPE for our team in Kenya, and we realized at that point that we were going to have to reprocess some of the masks, because we did not have the supply chain that was requisite,” Perkins said. “That was one of the reasons — in addition to thinking there could potentially be a shortage in the US — that we started this process.”

Shortages in protective gear, especially N95 face mask respirators, have gripped healthcare providers and facilities around the country and world amid the COVID-19 pandemic. The shortages spurred Gov. Michelle Lujan Grisham to ask citizens to refrain from purchasing N95 respirators and other PPE so that healthcare workers can have access to an adequate supply.

She later announced a public health order that prohibited medical supply providers or wholesellers from selling PPE without approval from the state.

RELATED: State announces new public health orders to protect PPE supply

Perkins was eager to get the word out about the protocol his team developed for decontaminating face masks, in part because institutions that may want to implement the process need to begin building up a reserve of used N95 masks to have on hand to decontaminate if and when the need arises.

“It is very important, if one is going to reprocess their PPE, that they begin saving their PPE. That’s the most important message,” Perkins said. “If PPE is discarded, then one does not have anything to go through this reprocessing procedure. It is extremely important to build up a reserve. It’s paramount.”

Hydrogen peroxide vapor

There are a variety of methods that can be used for decontaminating and sterilizing medical and protective equipment. Perkins said his team focused on processes that would work for N95 masks, which are complex pieces of equipment.

“When you decontaminate or sterilize them, you need to make sure you did not impact on properties of the mask,” he said. “We went to the literature to see what type of information was available, in terms of are there decontamination processes out there that can maintain filtration properties of the masks after that particular type of decontamination, and does it alter things like flow rate of particles and aeration for the user? Then you want to make sure the decontamination conditions also have the capacity to kill the pathogen that you’re trying to eliminate.”

Perkins and his team settled on a process using hydrogen peroxide vapor (HPV) to clean the masks and rid them of any contamination, including the SARS-CoV-2 virus.

Other institutions, such as the University of Nebraska and Duke University, have devised and published their own processes for decontaminating PPE. Duke University’s process also uses HPV, while the University of Nebraska’s process uses ultraviolet light.

Perkins said there were many factors that caused him and his team to go with HPV. For one thing, HPV generators, the machines that create the vaporized hydrogen peroxide, are common in hospital settings.

“A commonly-used method of decontamination and sterilization is hydrogen peroxide vapor. It’s oftentimes used in hospitals to decontaminate patient rooms,” Perkins said.

The HPV method also uses a biological indicator to determine whether the decontamination process has been successful. 

“A biological indicator oftentime represents a worst case scenario, a pathogen or organism that’s rather hardy,” he said. “The particular biological indicator is used to say, ‘during this decontamination or sterilization process, did I achieve the appropriate organism killing properties?’”

That will help healthcare workers determine if the decontamination was successful.

How it works

The procedure Perkins and his team developed works like this: First, the contaminated masks are carefully collected and stored after their first use. For the decontamination process, the masks are carefully removed from their storage packaging and inspected before being arranged on racks by the elastic ear straps.

“If there’s any makeup or biological material, or any damage to the mask, that mask gets discarded in a biohazard waste container,” Perkins said.

The masks are then wheeled into the decontamination room, along with the chemical and biological indicators. The room is then filled with vaporized hydrogen peroxide.

Perkins said his team initially ran into some trouble with using standard rooms to perform the procedure. Instead, his team was able to test out the process successfully in an empty operating room.

“The nice thing about operating rooms in general is that they have good environmental controls, rapid turnover of air flow within the room, and they also are constructed such that they don’t have fissures or cracks, so they’re relatively well-sealed rooms,” Perkins said. They are also available in most hospitals, and with elective surgeries now being postponed in hospitals across the state, there’s a higher likelihood that an operating room will be available at some point for decontaminating masks.

After exposure, the room is cleared of the vapor and the chemical and biological indicators are checked to determine if the process was successful. Finally, the masks are collected and inspected again to ensure the integrity of the respirators.

“When this decontamination procedure is done on a N95 respirator, the end user does a [final] visual inspection of the mask, makes certain that all the properties, including the elastic straps, are intact,” Perkins said. “Then the healthcare provider puts the mask on and does a fit test, to make sure the integrity of the mask is where it should be, and that there are no risks associated with that.”

The decontamination process lasts between three to four hours, and as many as 1,000 masks can be decontaminated at once using a single HPV generator, Perkins said.

“Start to finish, it takes a good day. And that’s when you have a reserve,” Perkins said. “You could, in 24 hours, if you had a reserve, and your instrument settings were correct and you had tested everything, with chemical and biological indicators, you could make a run within a day and do redistribution. But that’s a crew working diligently.”

In theory, a facility could process as many as 3,000 masks a day in a crisis situation, Perkins said.

Each mask can be decontaminated up to 20 times using this procedure, Perkins said, and possibly more. But because other studies have found the elastic ear straps tend to decay after more than 30 cycles, Perkins’ protocol is to run 20 cycles “and then reevaluate the integrity of the masks overall,” he said.

Getting the word out

Perkins seemed relieved that the protocol would be made available on the MedRxiv platform to those who might benefit from it.

“We hope institutions start using it,” he said.

And he was also grateful to the team that helped him develop the process.

“There is a large team working, but core individuals on the team have really worked diligently to make sure this process occurred safely and efficiently,” he said. “That would be Steve Villescas, Terry Wu, Tim Muller, Jens Langsjoen, Phil Seidenberg, Ivy Hurwitz and Tammy Fogg.”

“There are other team members that have made important contributions, but that’s really the core group of individuals who have brought this from a conceptual ideology to completion of the process successfully,” he said.