Peripheral pressures can be measured noninvasively by different techniques. For example, (calibrated) finger pressure can be reliably measured by photoplethysmography , and (un-calibrated) radial artery  and carotid artery pressure waveforms can be obtained with applanation tonometry . Both techniques are commercially available. However, most clinicians and family physicians use peripheral pressures and typically brachial pressure obtained with the classical sphygmomanometer. Brachial pressure, systolic and diastolic values only, is then used as a substitute for aortic pressure, or, even more so, as a global arterial pressure indicator. However, peripheral and central aortic pressures are not the same. The pressure waveform and the systolic and diastolic pressures can be substantially different between locations (see Figure in the box). In general, systolic pressure increases as we move from central to peripheral sites, a phenomenon called ‘systolic peaking’, which is attributed to wave reflections in the peripheral vascular beds. Diastolic pressure tends to be slightly lower in peripheral vessels than in central arteries. Recently is has been made clear that not only peripheral and aortic pressures differ in magnitude and wave shape, but that aortic pressure is a better indicator of cardiac morbidity and mortality than peripheral pressure . Also the effect of blood pressure lowering appears to have different effects on aorta and peripheral pressures [4, 5].
KeywordsTransfer Function Aortic Pressure Applanation Tonometry Peripheral Site Forward Wave
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