The Prospective Observational Study of ARDS Related Acute CorPulmonale and the Randomized Controlled Study of ARDS Aimed Circulation Protection China (ACPC)

Acute respiratory distress syndrome (ARDS) is an acute and critical illness characterized by progressive dyspnea and refractory hypoxemia caused by intrapulmonary or extrapulmonary factors. The mortality rate of ARDS is extremely high. ACP caused by pulmonary circulatory disorder is its main clinical feature, which is related to the severity of lung injury in ARDS patients. It has been recognized that the ACP is an independent risk factor for the prognosis of patients with ARDS. Positive pressure mechanical ventilation is an important ARDS treatment strategy for ARDS. Especially the lung protective ventilation strategy with "small tidal volume and increased PEEP" as the core content, which achieved a milestone of lower the mortality of ARDS. However, improper use of positive pressure mechanical ventilation can increase right ventricular load and increase mortality in ARDS patients. Therefore, understanding the effect of positive pressure mechanical ventilation on right heart function in patients with ARDS is important for prevention and treatment for the ACP of ARDS and reduction of ARDS mortality.

The alveolar edema, alveolar collapse, and hypoxic pulmonary vasoconstriction loss caused by increased pulmonary vascular permeability and release of inflammatory mediators resulted in loss of ventilation/blood flow, severe hypoxemia, pulmonary vasospasm, pulmonary microthrombus formation, which increased pulmonary arterial pressure and even APC. Positive pressure mechanical ventilation maintains alveolar ventilation through positive airway pressure, prevents premature alveolar collapse by positive end expiratory pressure (PEEP), changes intrathoracic pressure and lung volume, and affects the right ventricle load. Different studies have found that the incidence of ACP in patients with ARDS is from 22% to 60%. Jardin, et al found that patients with ARDS had a significant increase in ACP and mortality when the airway pressure was greater than 26 cmH2O, which revealed that the difference in positive pressure mechanical ventilation settings has a significant difference in the right heart function of ARDS patients. Mekontso, et al propose a simple clinical risk score for early identification of ACP included pneumonia as cause of ARDS, driving pressure ≥18cmH2O, PaO2/FiO2 ratio<150 mmHg, and PaCO2≥48mmHg. However, for the morbidity and mortality of ACP in ARDS, the related risk factors and criteria are different due to the influence of the different etiology of ARDS and the different study time. For these reasons, the investigators established a national cohort of Chinese ARDS with Acute CorPulmonale to enable prospective observational studies.