Validation of the transfer function technique for generating central from peripheral upper limb pressure waveform.

Central aortic pressure waveforms can be calculated from the radial artery pressure waveform using a generalized transfer function to correct for pressure wave distortion in the upper limb. Although validated to standards conventionally applied, reservations are still expressed on use of this process, because of the relatively small number of patients from whom appropriate invasive data were obtained. The study described here supplemented such data with noninvasive data obtained from carotid and radial artery tonometry in 439 patients and normal subjects. The carotid-radial artery transfer function was similar to the aortic-radial when allowance was made for wave travel from aorta to carotid artery. The carotid-radial transfer function was identical in male and female individuals, was similar at different arterial pressures and in mature adults. Differences are relatively small, are seen at frequencies where central pressure wave components are small and are similar to those seen with vasodilator agents in invasive studies. Findings provide further support for use of a generalized transfer function to calculate aortic from upper limb pressure and conform with previously established views on vascular impedance.