Measurement of Blood Flow Velocity Waveforms in the Carotid, Brachial and Femoral Arteries during Head-Up Tilt

The purpose of this study is to measure blood velocities in carotid, brachial and femoral arteries with synchronized measurement of electrocardiogram (ECG) during head-up tilt (HUT) using a developed telemetry measurement system. The velocity waveforms and ECG are continuously measured in six putatively healthy young subjects for 130 s during supine and 90 degrees HUT. From the measured peak systolic S1 and end-diastolic d velocities, we assess the velocity waveforms in 3 arteries by using an index of d/S1. The velocity waveforms, heart rate (HR), and blood pressure (BP) are assessed for 20 s at the stages of postural change. There is no significant change in the carotid index of d/S1, but there are significant increases in the brachial and femoral index. HUT induces increase in HR. However, BP does not change with tilt. A constant in the carotid index is due to the effect of cerebral autoregulation (CA) maintaining blood flow to the brain. In contrast, the index in the brachial and femoral is more influenced by venous pressure (VP) in postural change. In conclusion, this study demonstrates that synchronized measurement of blood velocity waveforms in carotid, brachial, and femoral in HUT using the telemetry measurement device is attainable.