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

We thank the authors for their kind and thoughtful comments on our work. We reported the pattern and degree of right ventricular (RV) dysfunction in 90 consecutive mechanically ventilated patients (42.2% VV-ECMO) with severe COVID-19 infection [[1]Bleakley C. Singh S. Garfield B. Morosin M. Surkova E. Mandalia M.S. et al.Right ventricular dysfunction in critically ill COVID-19 ARDS.Int. J. Cardiol. 2021; 327: 251-258Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar]. The authors raise the important issue of whether use of veno-venous extracorporeal membrane oxygenation (VV-ECMO) could impact RV function differently to conventional invasive ventilation. During VV ECMO, ‘rest’ ventilator settings minimise energy delivery to the lungs by reducing volumes but maintaining positive end expiratory pressure (PEEP). Therefore, overall intrathoracic pressures are lower than in conventional ‘protective’ low volume strategies that are limited by oxygenation requirements and acceptable carbon dioxide levels. Thus, differences in ventilation data between the groups demonstrated lower tidal volumes per ideal body weight (6.6 ± 1.3 vs 3.3 ± 1.4 ml/kg, p ≤ 0.001) and lower driving pressure (11.27 ± 2.9 vs 12.88 ± 3.7cmH2O, p = 0.01) in those on VV-ECMO. However, we do not have measures of total intrathoracic pressure, which is perhaps more relevant in the impact of ventilation on the RV. Indeed, there was no difference in pulmonary vascular resistance (PVR) (2.3 ± 0.9 vs 2.4 ± 0.9WU, p = 0.59) between groups. Therefore, it is not necessarily unexpected that measures of RV function did not differ significantly. Specifically, there were no differences in PA coupling by fractional area change (FAC) versus RV systolic pressure (RVSP) (0.61 ± 0.29 vs 0.69 ± 0.33, p = 0.26), or FAC (28 ± 11 vs 29 ± 8%, p = 0.82). As described [[1]Bleakley C. Singh S. Garfield B. Morosin M. Surkova E. Mandalia M.S. et al.Right ventricular dysfunction in critically ill COVID-19 ARDS.Int. J. Cardiol. 2021; 327: 251-258Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar], we believe that the correlation between markers of cardiac stress and deterioration in RV radial function indicates a degree of intrinsic myocardial injury or inflammation. Therefore, whilst the excellent points raised have been interesting to report on, we did not find that the mode of ventilation significantly impacted RV function. “This author takes responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation”.