Validation of a Device for High Fidelity Correction of Pressure Signals from Fluid-Filled Systems by Harmonic Analysis

Fluid-filled systems are generally used for invasive pressure measurements in cardiology, anesthesiology and intensive care medicine. Wave reflection and attenuation cause considerable signal distortion. The article presents the in vitro validation of a new commercially available device for the correction of distortion of pressures. Methods: The fluid-filled system consisted of different standard catheters, which were connected to the transducer using standard kits and alternatively lines of different length allowing a systematic variation of resonance frequency (6 Hz ? 30 Hz). Enhanced damping was simulated by interposition of a damping device (R.O.S.E.) in the line. Correction data were calculated from a measurement of the transfer function. Pressure was generated by a pressure generator (Biotek) from tip-pressure signals collected from different patients for left ventricular, aortic, right ventricular, pulmonalis and right atrial pressures. The corrected and the uncorrected pressure signals were compared with the reference pressure as to their impact on diastolic and systolic error and dP/dt. Results: A total of 360 signals (minimum length 1 min) were evaluated. Mean systolic (diastolic) errors in uncorrected signals ranged from 10.3±11.5 mmHg (6.9±6.7 mmHg) in left ventricles to 1.2±1.1 mmHg (0.7±0.4 mmHg) in pulmonary arteries. Mean systolic errors in corrected signals ranged from 2.3±1.2 mmHg (2.3±1.2 mmHg) in left ventricles to 0.6±0.4 mmHg (0.6±0.3 mmHg) in pulmonary arteries. Mean systolic errors of dP/dt in uncorrected (corrected) signals ranged from 636±463 mmHg/s (76±71 mmHg/s) in left ventricles to 67±40 mmHg/s (15±8 mmHg/s) in pulmonary arteries. The error of RA pressures was < 1 mmHg even in uncorrected pressure signals. Severe damping (rose) was associated with significantly elevated errors. Conclusions: Elevated standard deviations of errors in uncorrected signal reflect the unpredictable variability of pressure distortion. The corrector consistently achieves acceptable accuracy for absolute systolic and diastolic errors and dynamic distortion reflected by dP/dt in all tested systems and signals. It does not deteriorate accuracy in any case.