Moving On—On Average in the Right Direction?
Noninvasive Methods to Estimate Central Blood Pressure
See related article, p 865–870
For >100 years, aortic hemodynamics have been the subject of systematic physiological investigations. Already in the early days, Otto Frank introduced the Windkessel model to describe the aorta, in particular, its function as cushion against cardiac pulsatility, providing reduced pressure load to large vessels. In engineering terms, this behavior of the aorta can be described by a low-pass filter.
In contrast to the intermittent pumping left ventricle with consecutive pulsatile pressure and flow in the aorta and the large arteries, the microcirculation is designed to provide virtually steady blood flow at low pressure for the maintenance of proper organ perfusion. This modification of pressure and flow is achieved mainly by variation of vessel diameter and wall composition and can be monitored through changes in the amplitude and shape of pressure and flow pulses downward the arterial bed. With respect to the large arteries, central (ascending aortic) systolic pressures and central pulse pressures are lower than their counterparts at the sites of noninvasive blood pressure recordings (usually at the brachial artery), whereas diastolic pressure is almost equal. This effect is called aortic to peripheral systolic or pulse pressure amplification and depends among other factors on age and the elastic properties …