Where pulmonary arterial catheters go: intrathoracic distribution.

Recent experimental evidence indicates that the position of a pulmonary arterial catheter within the thorax is important because vertical height gradients from catheter tip to main pulmonary artery and left atrium may alter the validity of the pressure measured. The authors therefore examined the intrathoracic distribution of 314 pulmonary arterial catheters which at insertion were advanced to the most proximal position from which pulmonary wedge pressure could be obtained. Five catheters (1.8 per cent) were 6 cm or more cephalad to the carina, and 16 (5.1 per cent) were 9 cm or more lateral to the midline. With peripheral catheters recordings of pulmonary arterial and wedge pressures may be erroneous because future patient position, initiation of positive end-expiratory pressure, and occurrence of low pulmonary arterial and left atrial pressures may convert the region of lung in which the catheter tip lies to a Zone 1 of the lung.