古幡 博¹, 小松 一祐², 古平 国泰³, 藤代 健太郎³, 内田 智子³, 高津 光洋¹, 菅原 基晃⁴

Hiroshi FURUHATA¹, Kazuhiro KOMATSU², Kuniyasu KODAIRA³, Kentaro FUJISHIRO³, Tomoko UCHIDA³, Akihiro TAKATSU¹, Motoaki SUGAWARA⁴

¹東京慈恵会医科大学ME研究室, ²東京慈恵会医科大学医学情報センター, ³東京慈恵会医科大学内科4, ⁴東京女子医科大学附属日本心臓血圧研究所

¹Medical Engineering Laboratory, The Jikei University School of Medicine, ²Medical Information Center, The Jikei University School of Medicine, ³Internal Medicine IV, The Jikei University School of Medicine, ⁴The Heart Institute of Japan, Tokyo Women's Medical College

キーワード : Blood flow, Cardiovascular system, Doppler method, Power, Waveform

The traveling wave power (WP) in the blood flow was measured noninvasively at the common carotid artery (CCA) in 5 young and 5 elderly subjects. WP was defined as the product of differences in blood pressure (ΔP) and flow (ΔQ). The waveform of P was determined by calibrating change in the waveform of CCA vessel diameter (D-waveform), as determined by an ultrasonic echo tracking system (ETS), by the maximum and minimum values of brachial cuff pressure. A quantitative flow-measurement system (QFS) that used blood velocity, determined by the continuous Doppler method, and the vessel cross-sectional area, calculated from the D-waveform, was used to determine the waveform of Q noninvasively. The positive componet of WP indicates the power of the forward wave (F) in blood traveling from the heart to the peripheral regions, while the negative component indicates the power of the backward wave (B) in blood traveling from the periphery back to the heart. Positive WP generally appeared at the early systolic phase (F1 wave) and at the end systolic phase (F2 wave) in the cardiac cycle; negative WP appeared just after the F1 (B1 wave) and just after the F2 waves were detected (B2 wave). F1 wave energy in the WP waveforms of young subjects was 2.97±0.78×10^-6N·m, 1.84 times larger than the 1.52±0.78×10^-6N·m of elderly subjects. F2 wave energy was 0.145±0.039×10^-6N·m, 2.12 times smaller than the 0.307±0.077×10^-6N·m of elderly subjects. Negative B1 wave energy was -0.21±0.125×10^-6 N·m, 2.14 times larger than the -0.096±0.069×10^-6N·m of elderly subjects. In other words, the reflection component from the peripheral regions in young subjects was larger than that in elderly subjects. But rate of energy (B1 wave)/(F1 wave) did not differ significantly in either group, however: 0.067±0.025 in young subjects; 0.062±0.027 in elderly subjects. Thus, under normal conditions peripheral vascular properties may be nearly the same in young and elderly individuals. WP waveform would appear to be a useful index for studying the mechanical properties of the cardiovascular system.