Haemodynamic performance and weaning from mechanical ventilation following open-heart surgery

In 38 patients ventilated after open-heart surgery the effect of a 20 minutes spontaneous breathing period on right atrial pressure (RAP), left atrial pressure (LAP), pulmonary artery pressure (PAP), aortic pressure (AoP), ECG and cardiac index (CI) was monitored. Arterial bloodgas analysis before and during spontaneous breathing ruled out any respiratory failure. The test period of spontaneous breathing provoked an increase in systemic and pulmonary vascular resistance. By this and by a direct aggravation of cardiac failure the work of both ventricles dropped inspite of an increase in enddiastolic ventricular pressure. If these hemodynamic effects of a spontaneous breathing test period are taken as a guide for deciding, if a patient after open-heart surgery is ready for being extubated, the need for reintubation will be extremely rare. The study encourages us to sue mechanical ventilation as an additional instrument for treating heart failure even if no respiratory failure is present.