Prospective evaluation of a method for estimating ascending aortic pressure from the radial artery pressure waveform

Pressure wave reflection in the upper limb causes amplification of the arte rial pulse so that radial systolic and pulse pressures are greater than in the ascending aorta. Wave transmission properties in the upper limbs (in co ntrast to the descending aorta and lower limbs) change little with age, dis ease, and drug therapy in adult humans. Such consistency has led to use of a generalized transfer function to synthesize the ascending aortic pressure pulse from the radial pulse. Validity of this approach was tested for esti mation of aortic systolic, diastolic, pulse, and mean pressures from the ra dial pressure waveform. Ascending aortic and radial pressure waveforms were recorded simultaneously at cardiac surgery, before initiation of cardiopul monary bypass, with matched, fluid-filled manometer systems in 62 patients under control conditions and during nitroglycerin infusion. Aortic pressure pulse waves, generated from the radial pulse, showed agreement with the me asured aortic pulse waves with respect to systolic, diastolic, pulse, and m ean pressures, with mean differences <1 mm Hg. Control differences in Bland -Altman plots for mean SD in mm Hg were systolic, 0.0 +/- 4.4; diastolic, 0 .6 +/- 1.7; pulse, -0.7 +/- 4.2-, and mean pressure, -0.5 +/- 2.0. For nitr oglycerin infusion, differences respectively were systolic, -0.2 +/- 4.3; d iastolic, 0.6 +/- 1.7; pulse, -0.8 +/- 4.1; and mean pressure, -0.4 +/- 1.8 . Differences were within specified limits of the Association for the Advan cement of Medical Instrumentation SP10 criteria. In contrast, differences b etween recorded radial and aortic systolic and pulse pressures were well ou tside the criteria (respectively, 15.7 +/- 8.4 and 16.3 +/- 8.5 for control and 14.5 +/- 7.3 and 15.1 +/- 7.3 min Hg for nitroglycerin). Use of a gene ralized transfer function to synthesize radial artery pressure waveforms ca n provide substantially equivalent values of aortic systolic, pulse, mean, and diastolic pressures.