Assessment of the effects of inspiratory load on right ventricular function

The right ventricle (RV) plays a pivotal role during respiratory failure because of its high sensitivity to small loading changes during inspiration. Both RVs, preload and afterload, are altered during inspiration, either in spontaneous breathing or during mechanical ventilation. Some clinical situations especially affect RV load during inspiration, for example acute asthma and acute respiratory distress syndrome. The aim of this review is to explain and to summarize the different mechanisms leading to RV failure in these situations.

Research has recently reemphasized the importance to well known physiology of the venous return which is a contributor of RV preload. Authors recently focused on the mean systemic filling pressure which is one of the determinants of venous return. Venous return may change in opposite direction according to the type of ventilation (spontaneous or assisted). Recent works have also demonstrated the crucial impact of lung inflation and driving pressure on RV afterload, and have confirmed the deleterious effect of severe RV failure, described as acute cor pulmonale. In most situations of RV overload induced by inspiration, significant pulse pressure variations are observed, either called 'pulsus paradoxus' in spontaneously breathing patients or 'reverse pulsus paradoxus' in mechanically ventilated patients.

RV is very sensitive to abnormal inspiration, which is always responsible for an increase in its afterload. Pulse pressure variations, central venous pressure and especially echocardiography may monitor RV function in abnormal clinical situations. The pulmonary artery catheter was also proposed although now less used.