The proposed research project consists of two major parts: 1) collection of central aortic and peripheral BP data, and 2) evaluation of ITF methods using these data. BP data will be collected from the patients already undergoing procedures with cardiopulmonary bypass. Central aortic, radial and femoral BP waveforms will be simultaneously recorded. A non-invasive finger BP waveform will also be recorded. The pair of radial-femoral or finger-femoral BP recordings will be analyzed by the two-measurement ITF [3-5] to estimate individual-specific central aortic BP waveform. In addition, radial or finger BP recording will be analyzed by the single-measurement ITF [6] to estimate individual-specific central aortic BP waveform. The feasibility and validity of the methods in human subjects will be assessed by comparing the estimated central aortic BP waveforms with the measured central aortic BP waveforms. Its relative performance with respect to direct peripheral BP and existing NITF methods will be analyzed by comparing the difference between measured central aortic versus ITF-derived central aortic BP waveforms with those between measured central aortic versus direct peripheral and NITF-derived central aortic BP waveforms.