The open lung concept: effects on right ventricular afterload after cardiac surgery

Background. The open lung concept (OLC) is a method of ventilationintended to maintain end-expiratory lung volume by increasedairway pressure. Since this could increase right ventricularafterload, we studied the effect of this method on right ventricularafterload in patients after cardiac surgery. Methods. We studied 24 stable patients after coronary arterysurgery and/or valve surgery with cardiopulmonary bypass. Patientswere randomly assigned to OLC or conventional mechanical ventilation(CMV). In the OLC group, recruitment manoeuvres were applieduntil was greater than 50 kPa (reflecting an open lung). This value was maintained by sufficient positiveairway pressure. In the CMV group, volume-controlled ventilationwas used with a PEEP of 5 cm H₂O. Cardiac index, right ventricularpreload, contractility and afterload were measured with a pulmonaryartery thermodilution catheter during the 3-h observation period.Blood gases were monitored continuously. Results. To achieve > 50 kPa, 5.3 (3) (mean, SD) recruitment attempts were performed with a peak pressureof 45.5 (2) cm H₂O. To keep the lung open, PEEP of 17.0 (3)cm H₂O was required. Compared with baseline, pulmonary vascularresistance and right ventricular ejection fraction did not changesignificantly during the observation period in either group. Conclusion. No evidence was found that ventilation accordingto the OLC affects right ventricular afterload.