Severe COVID-19 Resembles Acute Respiratory Distress Syndrome

By Will Boggs MD

May 11, 2020

NEW YORK (Reuters Health) - Mechanically ventilated patients with COVID-19 can be managed like patients with acute respiratory distress syndrome (ARDS), according to a new report.

"In our paper, we use detailed patient-level data to show that oxygenation and lung mechanics in our patients with COVID-19 respiratory failure exist on a spectrum, are squarely consistent with 'typical' ARDS, and respond as expected to standard therapies, including prone ventilation," Dr. Jehan Alladina of Massachusetts General Hospital, in Boston, told Reuters Health by email.

As many as 20% of hospitalized patients with COVID-19 are admitted to the intensive-care unit (ICU), where as many as 88% are managed with invasive mechanical ventilation. Some reports have suggested that a significant proportion of COVID-19 respiratory failure is not the typical ARDS and warrants alternative management.

Dr. Alladina and colleagues describe the respiratory pathophysiology of 66 patients with COVID-19 who were intubated and admitted to the ICU. Of these patients, 56 (85%) met Berlin criteria for ARDS, with most having mild to moderate ARDS, the authors report in the American Journal of Respiratory and Critical Care Medicine.

On intubation, median positive end-expiratory pressure (PEEP) was 10 cm H2O, plateau pressure was 21 cm H2O, and driving pressure was 11 cm H2O. Static compliance of the respiratory system was 35 mL/cm H2O, and the estimated physiologic dead-space ratio was 0.45.

These findings are consistent with prior large cohorts of patients with ARDS, the researchers note.

Among the 31 patients who underwent prone ventilation, the median PaO2:FiO2 increased from 150 to 232 and median compliance increased from 33 to 36 mL/cm H20 after changing from supine to prone positioning.

These improvements in oxygenation and compliance with prone positioning are also consistent with prior studies of prone ventilation in early ARDS.

Immediately after returning to the supine position, PaO2:FiO2 was 217 and compliance was 35 mL/cm H2O, and 72 hours after initial prone ventilation, PaO2:FiO2 was 233 and compliance was 42 mL/cm H2O while supine.

After a median of 34 days of follow-up, 41 patients (62.1%) had been successfully extubated after a median duration of ventilation of 16.0 days, 50 patients (75.8%) had been discharged from the ICU, and 11 patients (16.7%) had died.

"We believe that our findings provide physiologic justification for the continued use of established ARDS therapies including low-tidal-volume ventilation," Dr. Alladina said. "(We) are highly concerned by the current discussion both in scientific journals and the lay press around abandoning these therapies. Early identification and supportive treatment that minimizes further lung injury are the only known therapeutic options that decrease mortality in ARDS, and the requisite level of evidence to change this approach should be set at the highest level."

"This is a small study with limited follow-up (although at minimum 30 days), and we need to be careful about making larger generalizations, particularly with regard to clinical outcomes," she conceded. "Moreover, our hospital has been fortunate to not have experienced as impressive of a surge as other cities and overall was not severely resource-limited. This is certainly an important factor that I don't want to downplay."

"This pandemic is a time of high anxiety and strong emotions for many, particularly for those affected directly by the disease but also for providers caring for patients," Dr. Alladina said. "There is a tendency to rely on anecdotes and a sense of urgency to do something."

"While I am certain that the biology of the novel coronavirus will continue to be better understood and am quite hopeful that we will find interventions to both prevent and treat the disease, until that time we must resist the urge to try new and unproven therapies at the expense of best supportive care and evidence-based medicine," she concluded.

SOURCE: https://bit.ly/3bdCatp American Journal of Respiratory and Critical Care Medicine, online April 29, 2020.

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