RV dysfunction in Covid-19 ARDS: Is there a difference in the impact of mechanical ventilation and ECMO?

We congratulate Dr. Bleakley and colleagues on their work [1]. To our knowledge, this is the first study on cardiac function in severe Acute Respiratory Distress Syndrome (ARDS) patients, equally distributed in two subgroups: with and without Extra Corporeal Membrane Oxygenation (ECMO). Right Ventricular-Pulmonary Artery (RV-PA) coupling was found impaired in most patients, which is in accordance to published data that mechanical ventilation settings [Tidal Volume (Vt) and Positive End Expiratory Pressure (PEEP)] affect Pulmonary Vascular Resistances (PVRs) [2]. Yet, RV parameters and performance (RV-PA coupling, RV radial function) might be quite different in patients under ECMO compared to non-ECMO Covid-19 ARDS patients.

Lung mechanics and ventilator settings are totally different under ECMO, enabling the use of ultra-protective ventilation. Tidal Volume, which negatively affects preload and PVRs, can be lowered to even 2.5 ml/kg [3]. Moreover, intense anticoagulation may be beneficial in pulmonary thrombosis, extensively recognized in Covid-19 ARDS [4].

On the other hand, lung mechanics in Covid-19 ARDS differ from classical ARDS [2,5]. Considering that lung compliance is rather preserved, application of high PEEP (according to guidelines) imposes an additional load on the injured pulmonary vasculature, without further recruiting the lung. Using tidal volumes almost twice those used under ECMO, although still lung protective, clearly further affect preload, PVR's, RV-PA coupling and RV performance. Even RV radial function in non-ECMO patients might also correlate to mechanical ventilator settings. Under this perspective, could the authors provide additional information concerning lung mechanics, ventilator settings and the corresponding RV parameters in these two distinct Covid-19 ARDS subgroups?

Declaration of Competing Interest

The authors report no relationships that could be construed as a conflict of interest.