Jury Out on Benefits, Harms of Ventilation Strategies for COVID-19

By Marilynn Larkin

June 08, 2020

NEW YORK (Reuters Health) - Evidence is lacking on the effectiveness of noninvasive ventilation (NIV) and invasive mechanical ventilation (IMV) for COVID-19 patients, and the safety of such strategies for healthcare workers, researchers say.

"What surprised us was the lack of better data to inform decisions, and the findings not being clearer," Dr. Holger Schunemann of McMaster University in Ontario, Canada told Reuters Health by email. "At present, both ventilation techniques seem to be similar," he said. But research to support that finding, "is often not well done and poorly reported."

"We also need better evidence about the risk of transmission of COVID-19 to healthcare workers while patients undergo ventilation or are prepared for it, because the virus may become aerosolized from an infected patient," he noted.

Dr. Schunemann and colleagues searched 21 World Health Organization and COVID-19 databases through April 2020 for studies comparing different oxygenation approaches in patients with coronavirus infections, including severe acute respiratory syndrome (SARS) or Middle East respiratory syndrome (MERS), or with hypoxemic respiratory failure. Studies evaluating the risk of virus transmission to healthcare workers from aerosol-generating procedures also were included.

As reported in Annals of Internal Medicine, 123 studies were eligible for inclusion: 45 on COVID-19; 70 on SARS; and eight on MERS. However, only five studies - one on COVID-19, three on SARS, and one on MERS - adjusted for key confounders.

One study in hospitalized patients with COVID-19 reported slightly higher mortality with NIV than with invasive mechanical ventilation (IMV), but two other studies - one in MERS and one in SARS - suggested a reduction in mortality with NIV (very low-certainty evidence).

Two studies in SARS patients reported a reduction in mortality with NIV compared with no mechanical ventilation (low-certainty evidence). Further, two systematic reviews suggested a large reduction in mortality with NIV compared with conventional oxygen therapy.

Dr. Schunemann said, "In the absence of clear evidence (of) harm for healthcare workers, NIV could be offered if there is maximal protection through personal protective equipment and precautions taken to avoid infection. Patients could receive helmet ventilation to avoid spreading aerosols."

But at this point, he added, "recommendations should be left to groups developing guidelines. Our evidence synthesis should be informative for (this purpose), even if the quality of evidence is still very low to low at this point."

As new studies are underway, he added, "we will keep this synthesis of the best available evidence on ventilation techniques alive and update it regularly...in collaboration with the Annals of Internal Medicine."

Dr. Kagya Amoako, Director of the Biomaterials and Medical. Device Innovation Laboratory at the University of New Haven in Connecticut commented in an email to Reuters Health, "The lack of evidence from systematic studies supporting transmission and infection via aerosol generation is a concern, although it doesn't take any stretch of imagination to acknowledge that the escape of exhaled viral-laden air can aerosolize and thus infect healthcare workers without the appropriate personal protection equipment."

"Both invasive and non-invasive ventilation strategies for the treatment of ARDS presenting SARS-CoV-1, MERS-CoV, and thus SARS-CoV-2 patients expose healthcare workers to the risk for transmission and infection, as those strategies are inherently aerosol-generating procedures," he said. "The intubation process itself brings expired air into close proximity with healthcare workers in IMVs, and exhaled breath escaping from NIVs into the care environment can potentially lead to exposure."

"Healthcare workers must therefore be aware of the risk of viral transmission and potential infection via aerosol generation whether using NIV methods such as CPAP, BiPAP or HFNC or using invasive ventilation requiring intubation on COVID-19 patients," he concluded.

SOURCE: https://bit.ly/3czA9bj Annals of Internal Medicine, online May 29, 2020.


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