Carotid Artery Applanation Tonometry Does Not Cause Significant Baroreceptor Activation

BACKGROUND: Carotid artery applanation tonometry is widely used in estimating local carotid artery pressure waveforms and carotid-femoral pulse wave velocity. However, the substantial pressure applied locally to the carotid artery with applanation tonometry might well evoke a baroreceptor response, resulting in bradycardia and hypotension. Therefore, when carotid and femoral tonometry are performed sequentially, baroreceptor activation could lead to different hemodynamic conditions between carotid and femoral acquisitions. Combining those acquisitions into one pulse wave velocity measure would be erroneous. In this study, we assessed whether carotid applanation tonometry has an influence on heart rate and blood pressure. METHODS: In 26 hypertensive subjects, heart rate and blood pressure were assessed by continuous finger pulse waveform recording during carotid as well as femoral applanation tonometry. Both carotid and femoral acquisitions were measured in alternation and in triplicate. Median averaging over the 3 carotid and femoral measurements, respectively, was used to obtain a subject's median heart rate and blood pressure during carotid as well as femoral tonometry. RESULTS: Difference in heart rate during carotid and femoral tonometry was -0.7±2.2 bpm. Differences in systolic, pulse, and diastolic blood pressure were -0.7±6.8, -0.1±3.8, and -0.3±3.5mm Hg, respectively. All differences were statistically nonsignificant. Confidence intervals were used to calculate the maximum absolute difference at 95% certainty, which was 1.6 bpm for heart rate and ≤3.5mm Hg for all blood pressures. CONCLUSIONS: We conclude that in our study, carotid artery applanation tonometry as performed by an experienced researcher did not cause clinically significant baroreceptor activation.