Right Ventricular Loading by Lung Inflation during Controlled Mechanical Ventilation.

Rationale: The inspiratory rise in transpulmonary pressure during mechanical ventilation increases right ventricular (RV) afterload. One mechanism is that when Palv exceeds left atrial pressure, West zone 1 or 2 (non-zone 3) conditions develop, and Palv becomes the downstream pressure opposing RV ejection. The Vt at which this impact on the right ventricle becomes hemodynamically evident is not well established. Objectives: To determine the magnitude of RV afterload and prevalence of significant non-zone 3 conditions during inspiration across the range of Vt currently prescribed in clinical practice. Methods: In postoperative passively ventilated cardiac surgery patients, we measured right atrial, right ventricle, pulmonary artery, pulmonary artery occlusion pressure, plateau pressure, and esophageal pressure during short periods of controlled ventilation, with Vt increments ranging between 2 and 12 ml/kg predicted body weight (PBW). The inspiratory increase in RV afterload was evaluated hemodynamically and echocardiographically. The prevalence of non-zone 3 conditions was determined using two definitions based on changes in esophageal pressure, pulmonary artery occlusion pressure, and plateau pressure. Measurements and Main Results: Fifty-one patients were studied. There was a linear relationship between Vt, driving pressure, transpulmonary pressure, and the inspiratory increase in the RV isovolumetric contraction pressure. Echocardiographically, increasing Vt was associated with a greater inspiratory increase in markers of afterload and a decrease in stroke volume. Non-zone 3 conditions were present in >50% of subjects at a Vt ⩾ 6 ml/kg PBW. Conclusions: In the Vt range currently prescribed, RV afterload increases with increasing Vt. A mechanical ventilation strategy that limits Vt and driving pressure is cardioprotective.

COVID-19-Related Acute Respiratory Distress Syndrome in a Pregnant Woman Supported on ECMO: The Juxtaposition of Bleeding in a Hypercoagulable State.

A 40-year-old pregnant woman at 28 weeks of gestation was diagnosed with severe acute respiratory failure syndrome (ARDS) due to coronavirus disease 2019 (COVID-19). She had severe hypoxemia despite the use of mechanical ventilation and muscle relaxant infusion. Veno-venous extracorporeal membrane oxygenation (VV-ECMO) was used, and she had a cesarian section while on ECMO support. She developed disseminated intravascular coagulation (DIC) with overt bleeding. This was managed by a multidisciplinary team (MDT) and a change of the ECMO circuit resulted in a dramatic improvement of her coagulation profile. Both the mother and the baby were discharged and went home in good condition.