Similarity between the suprasystolic wideband external pulse wave and the first derivative of the intra-arterial pulse wave

BACKGROUND: Wideband external pulse (WEP) monitoring, using a broad bandwidth piezoelectric sensor located over the brachial artery under the distal edge of a sphygmomanometer cuff, can be used for evaluating the contour of the arterial pressure pulse wave. The pulse contour contains valuable information relating to cardiovascular function which may be of clinical use in addition to blood pressure measurements. The aim of this study was to compare the shape of the WEP signal during inflation of the cuff to suprasystolic pressure, with intra-arterial pressure waves, after the administration of vasoactive drugs.

METHODS: Radial intra-arterial and suprasystolic WEP waveforms were recorded in 11 healthy men (mean 23 yr) before and at the end of infusion of glyceryl trinitrate, angiotensin II, norepinephrine, and salbutamol. Waveform similarity was assessed by comparing the timing and pressure of incident and reflected waves and by root mean square error (RMSE).

RESULTS: The WEP signal was found to closely resemble the first derivative of intra-arterial pressure. The WEP signal could be used to derive an arterial pressure wave with minimal bias in the timing of incident [- 8 (18) ms, mean (SD)] and reflected [- 1 (24) ms] waves. Augmentation index was underestimated by WEP [- 7 (18)%]. WEP also provided a measure of compliance which correlated with pulse wave velocity (r = - 0.44). RMSE values after the administration of each of the four drugs mentioned earlier were 12.4 (3.8), 17.7 (5.0), 22.1 (11.7), and 28.9 (22.4) mm Hg, respectively. Changes in derived WEP signals were similar to those measured by arterial line with all drugs.

CONCLUSIONS: The suprasystolic WEP signals can be used to derive arterial pressure waves which, although not identical, track changes in the intra-arterial pulse wave induced by vasoactive drugs.