Noninvasive Ventilatory Support in COVID-19: Friend or Foe?

Liam Davenport

April 07, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

With intensive care units (ICUs) in numerous countries overwhelmed in the face of the COVID-19 pandemic, many hospitals have turned to noninvasive ventilation (NIV) to stave off severe respiratory failure and ease the pressure on scarce resources.

This practice is seen as controversial by some US clinicians, but has been widely employed in China and is gaining traction in Europe, with the European Society of Intensive Care Medicine (ESICM) now recommending it.

And there is debate as to whether NIV devices — such as continuous positive airway pressure (CPAP), ordinarily used to treat conditions such as sleep apnea — should be the first port of call, or rather oxygen delivered by high-flow nasal cannula (HFNC).

Another concern is whether the benefits of using such interventions outweigh the risks of possible aerosolization of the virus, which could increase the risk of nosocomial infection. This issue may be especially pertinent when personal protective equipment for medical staff is in short supply

In some places, most notably Italy, helmet devices that cover the patient's head entirely — as opposed to the face masks typically used with other NIV — have been employed, which may help limit aerosolization.

CPAP or HFNC to Slow Disease Progression?

NIV is defined as a ventilation modality that supports breathing by delivering mechanically assisted breaths without the need for intubation or surgical airway. There are two main types: negative-pressure ventilation and noninvasive positive-pressure ventilation (NIPPV).

The latter is further subdivided into several subtypes, including CPAP and bilevel positive airway pressure (BiPAP).

NIV devices reduce the effort of breathing and help maintain inflation of the alveoli, thus increasing oxygenation.

Detailing the Italian experience of the COVID-19 pandemic, one expert observed that CPAP could be beneficial not only to reduce ICU admissions and the number of patients requiring intubation but also because nurses can administer it.

However, are CPAP and similar NIV devices the best choice?

ESICM issued one of the first international guidelines on the management of critically ill patients with COVID-19 in intensive care on March 23, as reported by Medscape Medical News.

ESICM suggests using oxygen delivered by HFNC as first-line therapy for patients with COVID-19 and acute hypoxemic respiratory failure in preference to NIPPV/CPAP, although the latter could be used "with close monitoring and short-interval assessment for worsening respiratory failure."

However, these are not recommendations, just suggestions, only supported by low-quality evidence, the society notes.

And in a study from China, HFNC was the most common ventilation support. Of patients experiencing severe acute respiratory failure because of COVID-19, 63% were treated with HFNC as first-line therapy and 33% were treated with NIV.

In contrast, the National Health Service in England has gone the other way; it recommends CPAP over HFNC, saying the latter is "not advocated in COVID-19 patients, based on lack of efficacy, oxygen use, and infection spread."

"We Don't Know the Effect of These Interventions on Patient Outcome"

Lead author of the ESICM guidelines Waleed Alhazzani, MD, McMaster University, Hamilton, Ontario, Canada, acknowledges that the discussion around NIV "is based on indirect evidence, communication with colleagues who treated a large number of COVID-19 patients, and common sense."

He told Medscape Medical News that in China and Italy "many COVID-19 patients received HFNC and NIPPV, but we don't know what the effect of these interventions on patient outcomes was."

And this is what most concerns Angela Rogers, MD, MPH, Division of Pulmonary and Critical Care, Stanford University, California.

She told Medscape Medical News: "My impression is that the majority of US institutions are not using NIPPV, but there is even tremendous controversy around HFNC."

This is "not only because of the risk of aerosolizing...but also because of concerns that patients can suddenly get much worse and that to intubate early may be the safest thing for patient care," she explained.

"[HFNC] is the topic that was most controversial for us here at Stanford, with people disagreeing strongly in both directions. Many great institutions [in the United States] are using [HFNC], many other great institutions are not," she said.

Risk of Infection From Aerosolization

What about the risk of infection from aerosolization?

In developing recommendations based on their frontline experience treating COVID-19, Massimiliano Sorbello, MD, AOU Policlinico San Marco University Hospital, Catania, Italy, and colleagues, recently writing in Anaesthesia, found that "all oxygen administration strategies in the spontaneous ventilating patient carry risks of aerosolization and disease transmission."

This was underlined by Lili Guan, MD, PhD, National Clinical Research Center for Respiratory Disease, Guangzhou, China, and colleagues, who reported on their experience in the European Respiratory Journal.

"The majority of patients are still receiving respiratory support through nasal catheter or common mask in general wards or emergency departments with limited medical resources," they said, noting that nosocomial rates of infection with COVID-19 in Chinese hospitals have been estimated at around 40%.

"Exhaled air dispersion during noninvasive respiratory support may increase the risk of coronavirus transmission and requires more attention from medical personnel," they note.

Alhazzani said that, although it is known "that NIPPV/CPAP is an aerosolizing procedure with increased risk of disease transmission," it may well be the same for HFNC.

"We don't know, as there are no good studies that looked at this," he told Medscape Medical News.

Editorialists writing about the ESICM guidelines in JAMA, agree: "Given the potential risks of inadvertent viral aerosolization using high-flow open circuits such as HFNC, more thorough examination of this potential source for disease transmission may be warranted."

"Currently, clinicians and decision-makers who are trying to contain the outbreak may be uncomfortable with the liberal use of HFNC and NIPPV, especially if prolonged, in crowded emergency departments or on hospital wards," they conclude.

Rushing Through New Machines and the Helmet Hope

Perhaps anticipating such use, however, the FDA has, in-line with other countries, announced urgent guidance on modifying respiratory devices, as long as they do not "create an undue risk."

"If the number of ventilators in your facility is running low, consider alternative devices capable of delivering breaths or pressure support to satisfy medically necessary treatment practices for patients requiring such ventilatory support," the guidance states.

This includes the use of devices for sleep apnea to treat respiratory insufficiency "provided that appropriate design mitigations are in place to minimize aerosolization," such as filters, it notes.

There is also hope that helmet-based ventilation may help reduce the risk of nosocomial infection — in this instance, a helmet replaces a facemask as the mode of delivery of oxygen.

The helmet consists of a plastic bell that fits over the head and attaches to a rubber collar neck seal, reminiscent of Victorian diving helmets. Their potential in the current pandemic was demonstrated in striking footage from Sky News showing a room full of Italian COVID-19 patients wearing the devices on an emergency ward.

The Italian version is more advanced than those available elsewhere — it was designed with a virus filter to prevent aerosolization and is more user friendly, with extra ports for medical staff to use.

However, the Italian helmet is not approved by the US Food and Drug Administration (FDA), although helmet devices have been trialed by the US National Institutes of Health (NIH) as a treatment for acute respiratory distress syndrome.

In any case, the Italian government has banned the export of helmet devices while it tackles its own COVID-19 crisis.

US hospitals are consequently turning to locally produced helmet devices, with companies seeing huge increases in orders.

Nevertheless, there are some notes of caution on the issue of helmets.

The ESICM guidelines describe them as an "attractive option" because they have "been shown to reduce exhaled air dispersion," but the authors emphasize that they are "not certain" about their safety or efficacy in COVID-19, and they were therefore "not able to make a recommendation regarding the use of helmet NIPPV compared with mask NIPPV."

Lorenzo Berra, MD, medical director of respiratory care at Massachusetts General Hospital, Boston, went a step further.

He told the Wall Street Journal that although the helmet device "could buy some time" for patients, he is "skeptical of using it for a huge number of patients, unless there are no ventilators."

Rogers has served as an advisor for Merck antibiotic trials (received no money) and has received research grants from the NIH and National Heart, Lung, and Blood Institute.

Intensive Care Med. Published online March 28, 2020. Full text

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