Wednesday, April 8, 2020



Dr K K Aggarwal
President Confederation of Medical Associations of Asia and Oceania
CDC Guidelines

367:  Extended Wear vs Reuse of masks

The CDC recommendations around optimizing the use of N95s fall into three categories: conventional, contingency, and crisis. Many hospitals in the contingency and crisis stages are implementing policies of extended use or limited reuse.

368: What are the strategies for mask conservation
The Infection Prevention Strategy (TIPS) that she has heard of nurses getting one mask per day, per week, or even every 2 weeks. Some nurses wear surgical masks over their N95 respirators to make them last longer, she noted.

In CDC guidance issued the agency pointed to studies demonstrating that the virus that causes COVID-19 can live on plastic, stainless steel, and cardboard surfaces for up to 72 hours.

The agency then suggested a passive decontamination strategy of sorts: issuing five respirators to each healthcare worker seeing COVID-19 patients. The worker wears each mask in the same order and places it in a paper bag at the end of the day. If done correctly, there should be a minimum of 5 days between each respirator's repeat use, the guidance notes.
Unused respirators that have passed the expiration dates on their labels can be used, per the CDC. But if a respirator is "compromised" or if a seal check fails, the respirator should be discarded and replaced.

369: What is Decontamination

Despite there being no CDC-approved method for decontamination, the agency said ultraviolet germicidal irradiation (UVGI), vaporous hydrogen peroxide (VHP), and moist heat have shown "the most promise" as methods for decontaminating respirators.
The FDA issued new guidance on March 29 explaining that during this public health emergency, the agency "does not intend to object to the distribution and use of sterilizers, disinfectant devices, and air purifiers that are intended to be effective at killing SARS-CoV-2 [the virus that causes COVID-19]

370: Is Ultraviolet Light effective

Light must reach every part of the mask and absorption levels have to be monitored.
UV radiation doesn't appear to harm the respirator's capacity for filtration.

371: What about vaporous Hydrogen Peroxide

Decontaminate N95 respirators for reuse using a VHP procedure that calls for 2.5 hours of exposure to concentrated gases and a maximum of 20 decontamination cycles per respirator.
VHP decontamination showed "minimal effect" on filtration efficacy and demonstrated "99.9999% efficiency in killing bacterial spores" and similar efficacy against bacteriophage viruses.
But the elastic bands themselves can degrade after about 30 cycles.

372: What about heat

A third method of decontamination, moist heat, has been studied at 60°C and 80% relative humidity.

In addition, Yi Cui, PhD, of Stanford University, and colleagues have experimental data suggesting that, although different, use of dry heat around 75°C for 30 minutes can also decontaminate N95 respirators and maintain filtration efficiency over several cycles.

But that process will require more research before it can be confirmed, he noted.

The CDC guidance also noted that decontamination with an autoclave, 70% isopropyl alcohol, microwave irradiation, and soap and water resulted in "significant filter degradation."

373: What Not to Do

  • Do not bake a respirator in a home oven, as it could expose the wearer and others to the virus
  • Do not use tanning lamps or nail dryers as a source of UV radiation, explaining that those lamps typically use UVA radiation that have a longer wavelength and do less damage to pathogens
  • Do not randomly redistribute decontaminated respirators; clinicians should write their names on their masks and each hospital should have a system to ensure they are returned to the appropriate owner
  • Masks are disinfected but not cleaned.

374: What are Homemade Substitute

As a last resort, homemade masks are "better than nothing,. They're more effective at "keeping the germ in than keeping the germ out."

Homemade masks are given to outsiders visiting patients or confirmed COVID-19 patients who are being sent home. The masks are laundered, and could in the future be used by clinicians to make their own N95s last longer.

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