How far would a million N95 masks go? It’s complicated, and this is why.

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On April 2, the New England Patriots’ team plane left China with mundane but suddenly precious cargo: 1.2 million N95 respirators, a critical type of mask that protects health-care workers treating patients who have infectious diseases.

Was that a big stash?

In normal, pre-covid-19 times, the answer would be yes. Most hospitals buy just a few thousand N95s per year, according to a company that negotiates purchasing contracts.

Image: Pallets of N95 respirator masks are offloaded from the New England Patriots' team plane on April 2 at Boston Logan International Airport. (Jim Davis/Boston Globe/Pool/AP)

In the frenzied weeks of March and April, when the trickle of covid-19 patients suddenly grew into a deluge, the answer was a hard no. Health and Human Services Assistant Secretary Robert Kadlec had testified in February that the United States would need 3.5 billion N95s in a serious pandemic.

By March, hospitals in areas with large outbreaks reported burning through the one-time-use masks at up to 10 times their normal rates.

Now in mid-May, as emergency supply lines have begun to kick in and reuse of hospital garb has become common, the answer is somewhere in between.

[Price-gouging, fraud and confusion plague a chaotic market for N95s]

Normal numbers don’t apply in the pandemic

N95s are key pieces of armor for front-line health-care workers who are battling an infectious respiratory disease. They are fitted to form a tight seal on the user’s face, and electrically charged fibers grab at least 95 percent of particles out of the air that passes through the mask.

Typically, 15 million to 20 million N95s would supply more than 3,000 hospitals for a year, said Cathy Denning, a senior vice president at Vizient, which negotiates health-care purchasing contracts for more than half of the roughly 6,100 U.S. hospitals. That averages out to about 5,000 to 6,600 per hospital per year, and many hospitals would stock far fewer.

Then came covid-19, and facilities near large outbreaks suddenly found themselves overwhelmed with patients and churning through N95s. During a nine-day stretch in late March and early April, New York City alone was averaging more than 1,500 new covid-19 hospitalizations per day, according to the city’s health department.

“If you look at New York-Presbyterian, for example, we heard that they were using 10 to 15 times their normal burn rate,” Denning said.

Using a few clues, we can figure out a rough idea of how many N95s would’ve been used if they were plentiful and hospital workers could wear and dispose of them after one use, according to pre-covid-19 best practices.

Denning said hospitals she works with have reported using 35 to 40 isolation gowns per covid-19 patient per day. If N95s were plentiful, they probably would be replaced as often as gowns.

According to the CDC, the median hospital stay of a surviving covid-19 patient is 10 to 13 days. That works out to between 350 and 520 N95s per patient.

Not all states report numbers of people hospitalized, but New York does, and on April 13, the state’s hospitals held 18,825 covid-19 patients. If caregivers used 35-40 N95s per patient, they would’ve used between 659,000 and 753,000 N95s that day. That would amount to more than half of the Patriots' planeload.

Caring for just those patients through their entire hospital stays would’ve required between 6.6 million and 9.8 million N95s, the equivalent of half to three-quarters of the 12 million unexpired masks that were in the federal government’s emergency stockpile at the beginning of the outbreak.

Of course, we know that N95s were not plentiful — and still aren’t in many places.

“Extremely scarce” is how New York-Presbyterian’s chief of surgery, Craig R. Smith, described his medical center’s N95 situation in a March 20 report.

In a late March letter to the White House, Rep. Scott R. Tipton (R-Colo.) said a shipment of supplies that included 49,000 N95s would be “enough for only one full day of statewide operations.”

[A Michigan congresswoman, a guy in China and a global scramble to find N95s]

Numerous scams and an influx of counterfeit N95s muddied the market, which had become a frenzy of desperate states, jurisdictions, health-care organizations and countries bidding against one another and sometimes against private individuals looking to hoard or resell personal protective equipment.

China, where the virus first emerged, produces about half of the world’s medical-grade masks. Production couldn’t meet the sudden demand.

[Early in the pandemic, U.S. government turned down offer to make millions of N95s in America]

Image: A patient is moved by emergency personnel at NewYork-Presbyterian Brooklyn Methodist Hospital on May 6.

Not all masks are the same

Researchers know that covid-19 spreads through droplets infected people emit when coughing, sneezing, talking or breathing; they don’t know whether it also spreads through airborne particles.

[Tracking coronavirus cases and deaths in the United States]

The CDC recommends that health-care workers who work very closely with covid-19 patients wear these pieces of PPE:

A properly fitted N95 respirator protects against droplets and filters out more than 95 percent of small particles that could contain viruses. N95s typically cost about 50 cents each and are made to be discarded after a single use.

An isolation gown is a type of surgical gown that has fluid-resistant panels covering the front and arms. They are usually used once and either discarded or laundered.

Gloves are also disposable and are usually made of vinyl, nitrile or latex. A caregiver for a covid-19 patient may wear two pairs at once.

Eye protection such as a face shield would be worn over an N95 to protect the eyes.

Hospitals use other types of masks as well.

Surgical masks are the most common. They are disposable and come in three protection levels. A surgical mask blocks droplets but not small particles.

The elastomeric half- or full-face respirator is reusable. Depending on the type of filter used, it can protect against 95 to 100 percent of very small particles and possibly vapors and gases. It doesn’t filter outgoing air, so it’s not suitable for a surgical setting, but the CDC's covid-19 guidelines say it can be an N95 alternative.

The most protective mask is a powered air-purifying respirator. With the correct filter, it blocks all particles and creates a personal fresh-air bubble. National Nurses United says these should be worn by people doing procedures that generate aerosol particles, such as intubations.

Mask shortages require making do

Faced with dwindling numbers of N95s and no reliable assurance of more in the immediate future, hospitals had to find ways to use fewer. Caregivers go from room to room wearing the same masks. Sometimes they wear the same masks for multiple shifts. Some places are attempting to decontaminate N95s for reuse.

Federal agencies such as the Food and Drug Administration and Centers for Disease Control and Prevention put out recommendations on how to get by with less, including grouping covid-19 patients together and allowing for the reuse — and, ideally, resterilizing — of “disposable” items, especially N95s.

National Nurses United, a union representing more than 150,000 U.S. registered nurses, says the new guidelines are too relaxed, and it has condemned widespread use of decontamination systems as “unacceptable and unsafe.”

“When employers require nurses to reuse the same N95 multiple times or for multiple shifts, they place the nurse and the patients at increased risk of exposure to SARS-CoV-2 as well as other pathogens that might be present,” said Jane Thomason, the union’s lead industrial hygienist, in an email. (SARS-CoV-2 is the official name for the coronavirus.)

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More than 1,000 health-care workers have died of covid-19 worldwide as of May 12, according to Medscape data.

Decontamination technology is promising but new, and research on its effectiveness against the coronavirus is sparse. A group of scientists and researchers studying decontamination practices advises that N95s may retain their effectiveness after being decontaminated somewhere between two and 20 times, depending on the method and the make and model of the mask.

Even with all the conservation and reuse, Denning said most hospitals are still going through N95 masks at four to five times their normal rates.

A fluid situation may be improving

Fortunately, the virus did not strike everywhere at once, and strategies such as social distancing have bought desperately needed time for many hospitals.

Manufacturers are stepping up U.S. production of N95s to try to meet the demand, both for now and for a potential second wave. For instance, 3M, the largest maker of N95s, said that it has doubled its worldwide production rate since January to 1.1 billion per year. Two U.S. Honeywell factories reportedly will produce 20 million N95s per month.

As of May 14, the Federal Emergency Management Agency had shipped nearly 92 million N95s; a White House initiative called Project Airbridge that began at the end of March distributed another 768,000 by early May.

[White House pandemic supply project swathed in secrecy, exaggeration]

To get supplies from manufacturers to places that need them, the American Hospital Association is conducting an effort called the 100 Million Mask Challenge, which began mid-March in Washington, the first state to see a covid-19 outbreak.

Organizers are venturing outside the traditional supply chain and even providing specs to companies that want to start production, said Priya Bathija, the AHA’s vice president of strategic initiatives.

As covid-19 surges into new areas, it has plateaued in some places that were in crisis a month ago.

Smith, the New York-Presbyterian surgeon who had written about the critical shortage of masks at his hospital in March, included a striking line in his April 15 update: “Today PPE is abundant.”

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A nurse’s experience with mask shortage: ‘It’s not safe at all’

Image: ICU nurses at a California hospital are given paper bags in which to store their N95s overnight. (Mawata Kamara)

Chiqui Esteban and Brandon Ferrill contributed to this report.

A previous version of this piece contained illustrations showing a type of N95 that has an exhalation valve, which would not filter exhaled air and would not be appropriate for some healthcare settings.

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Bonnie Berkowitz is a reporter in the Graphics department at The Washington Post who often focuses on Health & Science topics.FollowFollow