Background: Despite the large variation in pulse pressure waveform throughout the aorta, the diastolic decay of the pressure waveform is almost identical. We hypothesise that this is because there is a common reservoir pressure along the entire aorta, principally determined by the highly elastic proximal aortic root. We apply a new technique to calculate this reservoir pressure along the aorta to test this hypothesis.

Method and Results: Using intra-arterial wires, pressure and Doppler velocity were measured at 10cm intervals along the aorta in 16 patients (aged 55±11 years). Pressure was separated into reservoir and wave components using the new wave-reservoir technique. In all patients, the intra-subject reservoir pressure waveforms were almost identical (mean correlation coefficient 0.99±0.01) regardless of the marked changes in the measured pressure waveform (systolic pressure p=0.020 and pulse pressure p=0.001). Significant variation in reservoir pressure was seen between subjects (peak reservoir = 63.4 – 21.4 mmHg). The reservoir pressure was the predominate determinant of the pressure waveform and accounted for 67.0 ± 8.8% of the total integrated pulse pressure across all aortic sites.

Conclusions: The aortic pressure waveform is predominately determined by the reservoir pressure. This reservoir pressure is similar along the length of the aorta despite marked changes in the shape of the measured pressure waveform. Manipulation of the arterial reservoir, rather than wave-reflection sites may be more important in regulation of blood pressure control.