Intra-Arterial Blood Pressure Measurement: Sources of Error and Solutions

ABSTRACTRationaleIntra-arterial blood pressure measurement is the cornerstone of hemodynamic monitoring in Intensive Care Units (ICU). Accuracy of the measurement is dependent on the dynamic response of the measuring system, defined by its natural frequency (fnatural) and damping coefficient (Zdamping) which are estimated with a Fast-flush test. Locating the experimentally measured fnatural and Zdamping on the plot in the original paper by Gardner (1981) which defined the acceptable limits for these 2 parameters, has long been the only way to determine the accuracy of the pressure measurement.In this paper, we extend the current understanding of the effect of poor dynamic response of the measurement system, enhance the usefulness of Gardner’s plots by providing a numerical value for the error in pressure measurement (for a given set of conditions) and depict the gradation of error value as heat maps, and also demonstrate the usefulness of a tunable filter for error correction.Objectives(i) Estimation of the amplitude of error in pressure measurement through simulations based on real-world data, and development of heat-maps for easy use by physicians to assess if the recording conditions are optimal (ii) A new method to correct the error.Methods and ResultsSimulated blood pressure waveforms of various heart rates and pressure levels were passed through simulated measurement systems with varying fnatural and Zdamping. The numerical errors in systolic and diastolic pressures and mean error in the measured pressure were used to generate heat maps denoting the errors for the various recording conditions, in the same plot as that by Gardner (1981). Performance of a tunable filter to correct the error is demonstrated.ConclusionsIn many clinical settings the measurement of intra-arterial pressure is prone to significant error. The proposed tunable filter is shown to improve the accuracy of intra-arterial pressure recording.