Applied recording force and noninvasive arterial pulses

Arterial pressure pulses are often measured noninvasively, but the influence of external recording forces has not been well documented. Accordingly, the main goal was to delineate pulse contour and amplitude distortion with progressively compressive forces applied to an external transducer. Ten young normal male subjects were studied while supine. Pulses were recorded at the end of a normal expiration over a range of forces (0.45-4.29, 0.42N increments) applied in a randomized order over first the brachial and then the radial artery. Pulse contours were Fourier analyzed and harmonic powers were normalized to the peak power at the fundamental frequency. Brachial artery pulse amplitudes progressively decreased (p = 0.013), whereas, those at the radial artery peaked at a recording force of 1.79 +/- 0.01N (p < 0.001) and subsequently decreased parallel to the brachial data with larger forces. No significant pulse contour distortions occurred at either the brachial or radial artery with applied forces of up to 2.18 +/- 0.02 and 2.59 +/- 0.02N, respectively, as indicated by the similarity of the relative power for harmonics 2-7. Radial artery pulses were distorted at and beyond a force of 2.99 +/- 0.01N as indicated by the increased relative power of harmonics 3-7 (p < 0.05). Therefore, despite significant alterations in pulse amplitude, the relative shape of pulses remains similar over a large range of lower recording forces.