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Biomedical subjects

K Yamakoshi

Publications and source records attributed to K Yamakoshi.

At least 55 records · Page 3Linked to original sources
PubMed1985

A correlation analysis between pulse transit time and instantaneous blood pressure measured indirectly by the vascular unloading method.

Linear correlation coefficients (r) between pulse transit time (PTT) and blood pressure (BP) were evaluated on within-subject by within-condition level. Beat-to-beat systolic and diastolic BP was measured noninvasively using the vascular unloading technique (Yamakoshi, Shimazu and Togawa, 1980). PTT was determined from the time interval between the R-wave of ECG and the peak of the finger pulse wave. Five male subjects underwent a 2 min resting (RE), a 1 min cold pressor test (CP), eight 15 sec anagram tests (AN), and another 1 min CP. Significant r values were most frequently obtained for systolic BP and PTT in the RE condition. Under the CP or AN conditions, no consistent tendencies were observed. It was suggested that none of the r values are sufficiently high to warrant the use of PTT as an alternative index of BP. Some factors lowering the r values were discussed.

Adult↗
PubMed1985

Interaction between heart as a pump and artery as a load.

For a better understanding of the functional roles of the heart as a pump system, an analogy with an industrial fluid-pump system is beneficial. In this paper, the use of the ventricular pressure-volume relationship was shown to provide one of the most useful descriptions of the heart as a pump system. This description included the pump function of the ventricle as well as the interrelation between cardiac mechanics and energetics. In describing the heart only as a pump, Thévenin's network model consisting of a source of pressure with a series source resistance (or impedance) is useful in analysing the complex interactions of the equilibrium mechanism for determining cardiac output and arterial pressure, and the matching conditions under the ventriculo-arterial coupling during the ejection period for a given set of ventricular and arterial system parameters. The analytical results using this model explained previous experimental results by other investigators. It was also suggested that the ventriculo-arterial-coupled system appears to be matched. From the engineering point of view, it is desirable also for the ventricle as a pump to behave under such an optimum matching condition for delivering a maximum power to the arterial load.

Blood Pressure↗
PubMed1984

Venous occlusive RN plethysmography: comparison with electrical admittance plethysmography.

A venous occlusion plethysmography using radionuclide (RN) was introduced for the measurement of the limb blood flow. This technique, called RN plethysmography, can be carried out in a subject who has been previously administered RN intravenously for the routine angiographic examination. The blood flow is calculated from the initial slope of the RN count rate change (RN accumulation curve) due to venous occlusion. In this study, this method was compared with electrical admittance plethysmography. The blood flow values determined by these two methods correlated well with each other.

Biomedical Engineering↗
PubMed1983

[Vascular-volume compensation method for noninvasive measurement of instantaneous arterial blood pressure: its usefulness in psychological research].

A new method of measuring blood pressure proposed previously by us (1980) was examined to evaluate its usefulness and applicability for psychological research. In this method, beat-to-beat systolic and diastolic pressures and pressure waveforms of the human finger are measured noninvasively by the use of a volume-servocontrol system, in which vascular volume changes, associated with intraarterial pressure and photo-plethysmographically detected, are compensated by an applied counterpressure (cuff pressure) to maintain a proper value corresponding to the unloaded vascular volume. At this state, the servocontrolled cuff pressure follows the intraarterial pressure instantaneously. Comparative data with direct measurement from the brachial artery were analyzed in a normotensive and a hypertensive subjects, and fairly valid regression coefficients as well as highly significant correlation coefficients were obtained between these two methods in each subject under various conditions. The present system can be used without any discomfort for the measurement of instantaneous arterial pressure for more than one hour, since the blood circulation in the finger is maintained. This system, therefore, was found to be an useful and practical means to study human subjects in various fields of psychology.

Blood Pressure Determination↗