A Generalized Transfer Function Method for Reconstruction of Continuous Brachial Artery Pressure Based on Digital Measurement

Objective: To reconstruct brachial artery pressure (BAP) distally from digital artery pressure (DAP). Methods: We hypothesize that continuous BAP can simply be approximated by sum of two halves of the continuous DAP shifted by the delay time. In order to test it, we enrolled 30 healthy volunteers for two experiments. We firstly showed that the pressure wave in the digital artery can be considered twice as much as the forward/ backward wave in the finger. A simplified individualized transfer function was then derived so as to estimate BAP from DAP with the parameter of delay time estimated by tenfold cross validation. Finally, by comparing with a reference BAP, we found that the proposed method can correct the DAP. Result: The errors of the proposed method in estimating systolic and diastolic pressures are 0.4 +/- 6.2 and 0.7 +/- 3.7 mmHg, respectively. These results agree with the standard of Association for the Advancement of Medical Instrumentation (AAMI). Discussion: In our method, large arteries are modeled with a uniform, frictionless tube, while small arteries are represented as a terminal load. The unknown parameter of the delay time are estimated by tenfold cross validation. Conclusion: Our method is therefore promising in estimating continuous proximal blood pressure from peripheral blood pressure in practice.