Reconstruction of brachial artery pressure from noninvasive finger pressure measurements.

Abstract

Pulse wave distortions, mainly caused by reflections, and pressure gradients, caused by flow in the resistive vascular tree, may cause differences between finger and brachial artery pressures. These differences may limit the use of finger pressure measurements. We investigated whether brachial artery pressure waves could be reconstructed from finger pressure measurements by correcting for the pressure gradient in addition to correction for pulse wave distortion with a previously described filter. Finger artery pressure (with Finapres), intra-arterial brachial artery pressure (BAP), Riva-Rocci/ Korotkoff (RRK), oscillometric, and return-to-flow (RTF) measurements were simultaneously performed in 57 healthy elderly subjects and patients with vascular disease and/or hypertension. A generalized waveform filter was used to correct for pulse wave distortions. Correction equations for the pressure gradient, based on finger pressure, RRK, RTF, or oscillometric measurements, were obtained in 28 randomly selected subjects and tested in 29. Before reconstruction, Finapres underestimated mean and diastolic BAP (finger pressure minus BAP: systolic, -3.2 +/- 16.9 mm Hg; mean, -13.0 +/- 10.5 mm Hg; diastolic, -8.4 +/- 9.0 mm Hg [mean +/- SD]). After filtering, reconstructed BAP waves were similar to actual BAP in shape but not in pressure level. Optimal correction for the pressure gradient with an equation based on RTF measurements reduced the pressure differences to meet American Association for the Advancement of Medical Instrumentation criteria (reconstructed finger pressure minus BAP: systolic, 3.7 +/- 7.0 mm Hg; mean, 0.7 +/- 4.6 mm Hg; and diastolic, 1.0 +/- 4.9 mm Hg). BAP waves can be reconstructed from noninvasive finger pressure registrations when finger pressure waves are corrected for pulse wave distortion and individual pressure gradients.