key: cord-0894902-fs4htixp
authors: Yaroshetskiy, Andrey I.; Avdeev, Sergey N.; Konanykhin, Vasily D.
title: Acute Respiratory Distress Syndrome in COVID-19: Do All These Patients Definitely Require Intubation and Mechanical Ventilation?
date: 2020-11-15
journal: Am J Respir Crit Care Med
DOI: 10.1164/rccm.202007-2713le
sha: c212e181a8933854d97fbe53db12fa6be787a9d8
doc_id: 894902
cord_uid: fs4htixp

nan

Acute Respiratory Distress Syndrome in COVID-19: Do All These Patients Definitely Require Intubation and Mechanical Ventilation?

To the Editor:

We have read "Respiratory Pathophysiology of Mechanically Ventilated Patients with COVID-19: A Cohort Study" by Ziehr and colleagues with great interest (1) . In this letter, the authors described characteristics and outcomes in 66 patients with coronavirus disease (COVID-19) managed with mechanical ventilation. It is a great pleasure to see that 62.1% of these patients were successfully extubated after 2-3 weeks of mechanical ventilation. However, a few questions arose after reading the paper.

First, did all these patients definitely require intubation? Unfortunately, the authors didn't specify in their letter the indications they had used for intubation, as the higher proportion of successfully weaned patients might be explained by lower severity of COVID-19 pneumonia. As we can see from given data, the respiratory parameters at the ICU admission and during the first 5 days were not so critical. Second, why did 95% of patients receive vasopressors? A possible explanation can be seen in Figure 1 ). This can lead to lung overdistension and acute cor pulmonale. On the contrary, the reduced PEEP levels in patients with COVID-19 resulted in an increase in lung compliance and a decrease in dead space ventilation in a small observational study (5) . Deep sedation can be another possible explanation of the high usage of vasopressors (data not presented).

Third, why did the authors so often use neuromuscular blockade (in 42% of patients)? The benefit of neuromuscular blockers was shown in the ACURASYS trial, in which they were used in patients with Pa O 2 /FI O 2 less than 150 mm Hg in the first 48 hours of mechanical ventilation (6). If we look at Figure 1 by Ziehr and colleagues, we can see that only six patients (9%) had Pa O 2 /FI O 2 less than 150 mm Hg on Day 2. The neuromuscular blockade can lessen ventilator-induced lung injury by decreasing transpulmonary pressure swings in dependent lung regions in severe ARDS, but it is not the case for mild or moderate ARDS.

Finally, we have a question about the prone position during mechanical ventilation. The authors declared that median PEEP was 13 (interquartile range, 12-15) cm H 2 O while supine and 14 (interquartile range, 12-15) cm H 2 O while prone, so the PEEP levels in prone position did not decrease and even increased. This seems useless because a prone position that decreases the lung superimposed pressure must lead to a decrease in the PEEP levels.

We believe that the authors used invasive ventilation instead of noninvasive respiratory support in many cases because of known 

Respiratory pathophysiology of mechanically ventilated patients with COVID-19: a cohort study

High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure

Association of noninvasive oxygenation strategies with all-cause mortality in adults with acute hypoxemic respiratory failure: a systematic review and meta-analysis

COVID-19 does not lead to a "typical" acute respiratory distress syndrome

Advanced respiratory monitoring in COVID-19 patients: use less PEEP!

Neuromuscular blockers in early acute respiratory distress syndrome

Respiratory pathophysiology of mechanically ventilated patients with COVID-19: a cohort study

Copyright © 2020 by the American Thoracic Society This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0

Author disclosures are available with the text of this letter at www.atsjournals.org. 

Reply to Yaroshetskiy et al.

We conducted a retrospective observational cohort study focused solely on intubated patients with coronavirus disease (COVID-19) respiratory failure at two tertiary medical centers (1). It was not a clinical trial and did not include a nonintubated comparator cohort. Dr. Yaroshetskiy and colleagues raise important questions about the use of noninvasive respiratory support for COVID-19, but these are questions that our study was not designed to answer. We can only say that measures of gas exchange, respiratory system compliance, and positive end-expiratory pressure application in our patients were similar to those from prior large cohorts of acute respiratory distress syndrome (ARDS), as detailed in our manuscript. Patients were intubated according to standard clinical criteria and received established evidence-based care for ARDS at the discretion of the treating physician. This included prone positioning for patients with persistent hypoxemia or elevated airway pressures. Measures of gas exchange in patients receiving prone ventilation in our cohort were similar to those in published trials of prone ventilation for ARDS. Neuromuscular blockade was provided at the discretion of the treating physician, and shock was defined as the presence of any inotropes or vasopressors, regardless of level. n