A pressure and volume-limited inflation syringe

Excessive pressures generated in balloon-tipped pulmonary artery (PA) catheters, which have migrated distally, contribute to the morbidity and mortality associated with their use. A simple syringe modification is described by which additional dead space is added to the inflation syringe. The volume of injected gas is also increased to compensate for the dead space, thus ensuring correct balloon inflation. The added dead space acts as a compression chamber should normal balloon inflation be restricted (Safety Syringe). An additional modification is described in which the syringe nozzle is reduced to a pinhole, thus decreasing the rate of gas escape and lessening the possibility of rapid lateral impact of the balloon on the PA wall (Super Safety Syringe). The syringes were compared with a standard volume-limited syringe. Pressures were recorded at the intraluminal site of balloon contact in rigid tubes, live porcine PA, and human cadaver PA. The Safety Syringe consistently generated pressures of less than 975 mmHg, the lowest pressure at which human PA rupture has been demonstrated, under the most adverse simulated clinical conditions. The currently used volume-limited syringe generated a pressure of approximately 1500 mmHg when balloon inflation was restricted, and in one human cadaver PA, produced rupture. The pinhole modification of the Super Safety Syringe increased the time to generate maximum pressure from less than 0.25 s to about 1.5 s.