Clinical use of indices determined non-invasively from the radial and carotid pressure waveforms

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Abstract
To evaluate the clinical use of radial and carotid artery applanation tonometry as an independent supplement to cuff sphygmomanometry. In 44 patients, radial and carotid tonometric pressure recordings were taken at short intervals apart by two persons who had prolonged experience with both. Comparisons were made between directly recorded radial and carotid waveforms and between aortic waves synthesized from both, using SphygmoCor. Focus was on waveform features: time intervals between wavefoot and incisura, denoting ejection duration, between wavefoot and first systolic peak or shoulder T1, and augmentation index - the rise in pressure from this point to systolic peak divided by pulse pressure. No patient had discomfort with radial tonometry, whereas many found carotid tonometry uncomfortable. Beat-to-beat variability was lower for the radial than carotid site. The device's operator "quality index" was achieved for 78% of radial waveforms but just 20% of carotid waveforms (P<0.05). Interobserver variability was lower for all indices derived from radial, cf. carotid, waveforms. For the two observers combined, there was no difference between aortic indices determined from carotid and radial sites except for T1 (radial-derived 117+ or -17 ms, cf. carotid-derived 103+ or -17 ms, P<0.05), but this did not influence the value of augmentation index (radial-derived 26+ or -13%, cf. carotid-derived 28+ or -14%, P=NS). The present study conforms with most published results, and indicates superiority of radial to carotid tonometry in clinical practice.