Pressure and volume control for local drug-delivery catheters: development of a new microprocessor-controlled system

Local drug delivery is a potential solution to postintervention restenosis. Most catheters developed for local delivery depend upon control of pressure and of delivered volume for optimal performance. The present study was designed to assess the accuracy of current methods for inflation of local delivery catheters compared with a new microprocessor-controlled system specifically designed for this application.

An in vitro gravimetric testing system was constructed to record developed pressure and delivered volume using a variety of inflation devices and a microporous infusion catheter. Experienced catheterization laboratory personnel were given commercial angioplasty indeflators and a pressure-driven syringe and asked to quickly apply 5 atm and deliver 2.0 ml. A new microprocessor-controlled system was then tested using the same protocol.

The time required to reach a plateau pressure was lowest with the pressure-driven syringe (0.164 +/- 0.017 s) and much higher with standard indeflators (2.94 +/- 2.54, 4.64 +/- 2.98, 7.69 +/- 4.89, 8.28 +/- 6.31 s). The corresponding microprocessor-controlled value was much lower than that of the manual systems (0.84 +/- 0.37 s). The variability of plateau pressure, as measured by the standard deviation, was lowest with the pressure-driven syringe (0.029 +/- 0.014 atm) and highest with the manual systems (0.37 +/- 0.26, 0.40 +/- 0.18, 0.44 +/- 0.31, 0.32 +/- 0.10 atm). The microprocessor-controlled system also produced very little variability in pressure (0.08 +/- 0.004 atm). The volume delivered varied significantly with all manual devices (1.77 +/- 0.64, 1.74 +/- 0.66, 1.36 +/- 0.45, 1.80 +/- 0.33 ml) as well as with the pressure-driven syringe (1.86 +/- 0.32 ml), but the volume delivered by the microprocessor-controlled system was highly accurate (1.99 +/- 0.06 ml).

Manual inflation devices do not allow precise control of pressure or volume when used with local delivery catheters. Use of a pressure-driven syringe minimizes pressure error, but does not deliver an accurate volume. The microprocessor-controlled system minimizes pressure and volume error and should maximize transfer efficiency for local delivery catheter systems.