Hypotension secondary to balloon inflation of a pulmonary artery catheter.

Inflation of a balloon-tipped catheter for measurement of pulmonary artery wedge pressure caused a decrease in systemic arterial blood pressure in a mechanically ventilated patient after pneumonectomy. Obstruction by the balloon of a significant proportion of the cross-sectional area of the pulmonary circulation results in increased right ventricular afterload with subsequent decreased cardiac output and left atrial pressure. This decreased left atrial pressure can be measured accurately by the inflated balloon-tipped catheter but may be falsely low.