EVALUATION OF DYNAMIC PERFORMANCE IN LIQUID-FILLED CATHETER SYSTEMS FOR MEASURING INVASIVE BLOOD-PRESSURE

Invasive blood pressure measurement is used in patients with unstable haemodynamics. The demand of the accuracy of these measurements is hig h. The reliability of the reproduced signal strongly depends on the me asurement system's dynamic characteristic - its resonance frequency an d damping factor. These characteristics were examined with the frequen cy response method, which is valuable for second and higher order syst ems. Most of the pressure measuring systems in use in clinical practic e have low damping factor (0.1-0.2), which causes high overshoot in sy stolic pressure values (up to 13%), since putting all the measuring co mponents in a chain reduces the dynamic properties of a single compone nt and the resonance frequency drops drastically from over 100 Hz to e ven below 10 Hz. One of the solutions to increase the damping ratio is to insert a damping device R.O.S.E. parallel to the tubing. The reson ance frequency remains the same, the damping factor increases to aroun d 0.5. Systems with higher damping factors (0.5-0.7) have lower oversh oot (1-2%), therefore the blood pressure measurements are more accurat e.