ABSTRACT
Wedge tracings obtained at substantially less than full inflation volumes suggest distal migration of the catheter tip. Such migration may result from a combination of forward thrusting
of the catheter with each heart beat and loop shortening caused by catheter softening. Poor wedging may also result from patient movement with resultant catheter
displacement, or from the administration of PEEP or other forms of mechanical ventilation. The term overwedge refers to a pressure tracing that continues to rise, eventually exceeding the limits of the scale. Balloon inflation causes the distal lumen to impact the pulmonary artery intima and occlude the distal lumen. The distal lumen pressure rises because the catheter is flushed at a continuous rate of 3 ml h-1 with the pressure generated to reach 300 mmHg to flush the catheter. In Figure 5.3, the tracing suggests that the catheter is positioned too distal into the pulmonary artery, which increases the risk of perforation.
