June 4, 2021

DIY Duckbills and Renegade Respirators: How a Hospital Weathered the COVID-19 PPE Shortage

By Ed Rutkowski

June 4, 2021—When Dr. Devon Hahn heard about the coronavirus spreading through Wuhan, China, in late 2019, her first reaction was professional curiosity. A pediatrician and assistant professor at the University of Oklahoma’s Health Sciences Center in Oklahoma City, she knew that several strains of coronavirus cause bronchiolitis in infants, which is the number one reason that babies are admitted to hospital. “Medically speaking, we talk about coronaviruses all the time,” Dr. Hahn said in a recorded presentation broadcast as part of Virtual AIHce EXP 2021. “Hearing about a coronavirus that has different effects on humans was, at first, interesting—and then it became terrifying.”

The first COVID-19 patients were admitted to OU HSC in late spring 2020. Staff didn’t know what to expect. They were instructed to wear full PPE for long periods of time. “We weren’t even sure how it was being transmitted,” Dr. Hahn said. “Our lives became gowns, gloves, goggles, and N95s.”

Normally, N95 filtering facepiece respirators were used only when staff treated patients suspected of having tuberculosis. Their use indicated the potential seriousness of the COVID-19 threat. And then the supply of N95s dried up. Staff wore the same device for multiple shifts, and then for days on end. Seeking to ease the shortage, the Food and Drug Administration issued a series of Emergency Use Authorizations that allowed imported, non-NIOSH-approved FFRs such as KN95s, as well as the use of respirators that had been decontaminated.

OU’s approach to the N95 shortage was to develop alternative PPE, adopt CDC guidance for the extended use and reuse of PPE, and decontaminate N95s using in-house techniques. This approach helped preserve limited supplies but caused concern among OU doctors, Dr. Hahn said, who worried they were putting patients and staff at risk. In addition, the logistics of decontamination proved complicated. Staff were required to put their devices in envelopes at the end of their shift, to be sent off for decontamination. When the decontaminated respirators were returned, staff had to search for their own devices. “The whole system was very clunky,” Dr. Hahn said.

Other aspects of OU’s approach were more promising. Ken Marold, an assistant professor in the College of Architecture, designed a 3D-printed respirator that could be heat-molded to improve fit. Dubbed the Renegade Respirator, the device “looks a little bit like a tie fighter from Star Wars,” Dr. Hahn said. Evan Floyd from OU’s College of Public Health tested its filtration efficiency and suggested design improvements. Eventually the Renegade Respirator was granted an FDA EUA.

The key moment for Dr. Hahn was when she learned that the sterilization wrap hospitals use to autoclave surgical instruments has greater than 95 percent filtration. Using scissors, pipe cleaners, a cutting board, and lots of surgical wrap, she created masks with a familiar “duckbill” design. Early attempts used a wire for the nose bridge; eventually she switched to a foam material from a product used to seal windows, which was more comfortable for users.

Following Dr. Hahn’s presentation, Floyd joined the broadcast to discuss the testing regimen he developed to evaluate the fit and filtration efficiency of masks used at OU’s Children’s Hospital, including an N95, a KN95, and Dr. Hahn’s “DIY Duckbill” design. His study measured filtration efficiency and fit over the course of seven days. The N95, unsurprisingly, was the highest performer in both categories, but the straps had to be replaced on some of the masks. This was a common problem; elsewhere in the OU health system, Floyd said, straps were breaking after two days of use.

Straps were a problem for the KN95, too. Wearers at OU used paper clips to alleviate fatigue from the ear loops, Floyd said. This practice may have actually enhanced the fit of the KN95s: in Floyd’s study, the fit-test results for the KN95 started poor but improved over time—possibly due to an increase in tension from the paper clip kludge—while the filtration efficiency kept pace with the N95 through five days before dropping off on the seventh day.

And what about Dr. Hahn’s DIY Duckbill? “All in all, it held up quite well,” Floyd said. At the beginning of the study its filtration efficiency was only slightly behind that of the N95. The gap grew larger over the course of seven days, but it outperformed the KN95 on day 7. As for fit, the DIY Duckbill’s mean fit factor ranged from 23 to 12 over seven days—not nearly as good as the N95, but good enough in an emergency, Floyd said.

Floyd ended his presentation with an important caveat: “Filtration efficiency isn’t everything,” he said. “A mask has to fit you in order for it to filter those particles and provide the protection that’s necessary.”

Ed Rutkowski is editor in chief of The Synergist.