Well before SARS-CoV-2 began rampaging the globe, two virologists — one Dutch, one American — worried that just such a virus would explode and strike healthcare workers particularly hard.
The scientists, Vincent Munster, Ph.D., and Seth Judson, Ph.D., knew that the MERS and SARS coronaviruses had infected medical workers at alarmingly high rates. And they knew one reason why: many of these providers had performed or been present for, life-saving procedures that generated virus-laden aerosols.
Some healthcare workers had administered chest compressions. Others had performed bronchoscopies or tracheal intubations, airway-irritating procedures that can trigger forceful coughs and, in the process, release highly infectious aerosol clouds.
In a prescient paper, published two months before SARS-CoV-2 surfaced in China, Munster and Judson warned that emerging viruses, having jumped from animals to humans, would likely threaten the lives of doctors and nurses on the front lines.
“The viruses that pose the highest risk to healthcare workers performing aerosol-generating procedures may be some of the viruses that we know the least about,” they cautioned.
Of course, now we know about SARS-CoV-2.
Every day, nurses and doctors caring for Covid-19 patients perform the very procedures linked to provider infections during the outbreaks of Severe Acute Respiratory Syndrome (SARS) in 2002 and Middle Eastern Respiratory Syndrome (MERS) in 2012.
“During these procedures, viral particles can remain suspended in the air with a half-life of approximately 1 hour and be inhaled by those nearby,” a team of critical-care physicians cautioned in Circulation.
As the team noted, procedures such as CPR and tracheal intubation are often performed in tense, high-stress situations, as patients go into shock or cardiac arrest, their oxygen levels plummeting. Sufficient personal protective gear may not be at hand. Lapses in infection-control practices happen.
In these trying circumstances, healthcare workers need extra protection from infectious aerosols. Hospitals must look beyond face shields and respirators and consider the larger critical-care environment, ensuring appropriate room ventilation and outfitting ICUs and ERs with air dis-infection technology.
Aerosols Aloft: “Healthcare staff are extremely stressed”
When tuberculosis patients can’t cough up secretions on their own, they’re given a nebulized saline solution to inhale. This procedure, sputum induction, promotes coughing and can generate infectious aerosols. So can bronchoscopy, also performed often on TB patients.
Some years ago, the emergence of drug-resistant tuberculosis — now a serious global health threat — spurred concern about the potential risks of aerosol-generating procedures such as these. But it was the SARS outbreak that sounded a louder alarm.
During the eight-month, 29-country outbreak, infection rates among healthcare workers were astonishing: among SARS patients overall, 21% were healthcare workers. In Singapore, medical workers accounted for 40.8% of cases and in Toronto, 51%.
Initially, scientists assumed the SARS coronavirus was spread only via large droplets and close contact, the same assumption initially applied to SARS-CoV-2. But researchers later found cases in which droplet transmission simply “could not have been feasible.”
In one instance, chest compressions and tracheal intubation were performed on a SARS patient in respiratory failure. Three days later, one of the nine healthcare workers present tested positive for the virus — even though she’d worn two pairs of gloves, two gowns, safety glasses, a face shield, shoe covers, a hair cover, and an N95 respirator.
What’s more, she had not been involved in the CPR or intubation; her job was to insert an IV catheter into the patient’s left foot.
Had the nurse inhaled aerosols generated by those procedures? It’s impossible to know. And it would be near-impossible to capture air samples while providers converge around a desperately ill patient. (Air samples isolated during sputum induction of TB patients have proven to contain viable TB aerosols.)
Still, retrospective SARS studies make a compelling case.
For example, a Canadian team analyzed the treatment of 7 hospitalized SARS patients and the infection rate among the 122 healthcare workers who cared for them.
Compared to staff never involved in tracheal intubation, those present just prior to and during intubations were at “substantially increased risk” of contracting SARS.
Studies like these have alarmed today’s critical-care workers.
“Healthcare staff are extremely stressed about managing Covid-19 patients,” says Jerry Nolan, M.D., a CPR expert and chair of the European Resuscitation Council.
Which Procedures Generate Aerosols?
There’s no definitive list of aerosol-generating procedures and a fair amount of controversy on the topic. For example, over the years, the World Health Organization (WHO) has listed, de-listed, and then re-listed CPR as an aerosol-generating procedure.
At the moment, says Dr Nolan, “a consensus is evolving that chest compressions are highly likely to be generating, at the very least, droplets and probably airborne particles.”
Performing CPR on Covid-19 patients appears to be so risky that experts have issued unprecedented guidelines for providers.
Typically, doctors and nurses spring into action to perform chest compressions; now, they’re being advised to “take a pause” and consider whether there may be a less perilous alternative.
CPR and endotracheal intubation are considered by most health organizations to generate aerosols. In addition, the World Health Organization (WHO) lists bronchoscopy, open suctioning, manual ventilation before intubation, turning a patient to the prone position, and disconnecting a patient from a ventilator.
The U.S. Centers for Disease Control and Prevention (CDC)’s list is less definitive. However, the CDC considers endotracheal intubation to be “especially hazardous,” as high viral loads of SARS-CoV-2 are found in sputum and upper respiratory secretions of patients with Covid-19.
Drs. Munster and Judson divide aerosol-generating procedures into two categories: 1.) those that mechanically create and disperse aerosols, such as CPR, intubation, and bronchoscopy, and 2.) those that induce the patient to produce aerosols, such as ventilation, suctioning, and nebulization.
Protect Medical Workers with Air Dis-infection Technology
It may take years for scientists to agree on which procedures generate aerosols, but front-line medical workers don’t have the luxury of time. They have patients in cardiac arrest and respiratory distress, and they need immediate protection from any SARS-CoV-2 particles wafting about.
So, healthcare workers are innovating. At some hospitals, they’re performing endotracheal intubations through clear plastic drapes outfitted with armholes or through a plexiglass box, known as an aerosol blocking shield, that fits over the patient’s head.
Still, these devices haven’t been well studied and may limit the anesthesiologist’s view and/or range of motion. Also, they’re designed for intubation and won’t help with the half-dozen other procedures likely to generate aerosols.
Certainly, all hospitals are trying to limit scenarios that would prolong aerosol exposure, such as failed intubation attempts, by assigning their most experienced clinicians. But this pandemic is an all-hands-on-deck situation. The best person for the job may not always be available.
Of course, for any procedure, the most critical protection is personal protective equipment (PPE). Both WHO and CDC recommend healthcare workers present for aerosol-generating procedures wear an N95 or higher-level respirator, eye protection, gloves, and a gown.
But PPE shortages have been dire worldwide, and in emergency settings, even a complete ensemble may not offer full protection. The Toronto nurse who contracted SARS despite wearing extensive PPE was not an isolated case.
Lab studies confirm the limits of PPE. For example, an Israeli team simulated endotracheal intubation using a fluorescent marker to visualize exhaled respiratory particles. They found fluorescent markers on the uncovered facial skin, hair, and shoes of personnel “performing” the intubations, even though all wore required PPE. It’s well known that viral particles on clothing can be re-launched airborne.
The upshot: PPE “may not fully prevent exposure” to aerosols generating during emergency endotracheal intubation.
Given the limits of these and other common precautions, hospitals are recognizing they must protect workers by optimizing the larger critical-care environment.
Ideally, all aerosol-generating procedures would be performed in negative-pressure isolation rooms; the ventilation system allows air to flow into, but not escape from, the infected patient’s room.
But in the United States, for example, only 2% to 4% of all hospital rooms are equipped for negative pressure, and hospitals hard hit by Covid-19 may not have the resources to quickly convert other spaces.
What’s more, even rooms designed for negative pressure may not do the job. In a study that analyzed over 600 of these rooms, just 32% met ventilation standards.
It’s important, then, for hospitals to provide workers with an additional layer of protection: ultra-low-energy plasma technology by Novaerus.
Commonly installed in ICUs and emergency departments, Novaerus air dis-infection devices operate continuously and are safe around the most vulnerable patients, including Covid-19 patients in respiratory or cardiac distress.
Novaerus technology kills 99.99% of MS2 Bacteriophage, a surrogate for SARS-CoV-2, in 15 minutes, laboratory testing shows.
The protection extends far beyond Covid-19 and other coronaviruses. Novaerus technology kills other highly contagious viruses, such as influenza, norovirus, and measles, as well as dangerous bacteria and fungi that plague hospitals, such as MRSA, Clostridium difficile, and Aspergillus niger.
In an interview for the This Week in Virology podcast, conducted two years before SARS-CoV-2 was unleashed upon the globe, Vincent Munster of the U.S. NIH, an expert on MERS-coronavirus, was interviewed about the pandemic potential of coronaviruses.
“As virologists, we always kind of work from a worst-case scenario,” he told the interviewer.
SARS-CoV-2 has become that worst-case scenario.
The virus has overwhelmed the world’s healthcare systems, infecting more than 5 million people and killing more than 350,000 — and counting.
To prevent the pandemic from inflicting even more damage, on healthcare workers and patients alike, hospitals must deploy all available weapons, including air dis-infection technology.