Real-Time Accuracy Evaluation of Arterial Catheter Transducer Systems

Introduction

Arterial pressure is currently monitored in ICU with a catheter–transducer fluid line. This fluid filled tubing line distorts the original waveform due to its dynamic characteristics (natural frequency, Fn, and damping coefficient, z), introducing potentially significant errors when calculating the cardiac output from pulse contour signal analysis.

Methods

In our study, we cross-compared Fn and z obtained with our new Fast External Pressure Test (FEPT) and with the Fast Flush Test (FFLT), to the reference technique (Sine wave variable Frequency Analysis Test - SFAT). It was carried on a testbench for 48 hours. Fn and z were measured using the three techniques with two fluid-filled tubing lines (standard, STD, and blood conserving device, BCD).

Results

Fn measurements with FEPT and FFLT present similar biases (0.79 vs 0.83 Hz), but lower variability for FEPT, with limits of agreement (LOA) ranging from −3.35 to +4.99 Hz for FFLT vs −2.29 to +3.86 Hz ($p<0.0001$) for FEPT. For the measurement of z, FEPT has a bias of 0.047 and LOA of −0.063 to +0.157, much lower ($p<0.0001$) than those measured with the FFLT (bias 0.139 and LOA −0.028 to +0.306).

Conclusion

When automated, the FEPT method will detect potential situations of over/under estimations occurrences. This will prevent false alarms, alarm fatigue and therefore consequences on patient care. Eventually, FEPT turns to be more accurate than FFLT, less scattered, less time-consuming, less invasive and so well suited for use in clinical settings.