Ventricular pacing has recently become widely popular along with notable improvements made in the engineering aspects, and its application has gradually widened.
In our experiments, permanent and temporary pacings have been used respectively on the patients suffering from complete A-V block and on those in postoperative state with satisfactory results.
However, in some patients, who had been in far advanced cardiac dysfunction, ventricular pacing itself has been found inadequate to improve deteriorated postoperative cardiac functions, although it has proved sufficient to control arrhythmias. The reason is based on the negation of atrial contraction which is known to boost cardiac function up to 20 to 30 per cent when it is synchronized with ventricular contraction.
Subsequently, we have developed a new A-V sequential demand pacemaker to apply temporarily to patients immediately after open heart surgery and confirmed its electrical safety and reliability along with satisfactory hemodynamic response.
In this paper, we report the results obtained from this device, putting special emphasis on its R-wave sensibility.
To make clinical application easier, unipolar stimulation was used on the atrium and the ventricle. However, the problem which related to unipolar stimulation was the interference against ventricular demand mechanism by the atrial stimulation, resulting in malfunction of the demand system.
After investigating the property of this interfering wave in detail, we found that the cause was in the indifferent electrode.
Two methods of sensing R-wave are introduced. One employs a simulator which cancels the interfering wave for the ventricular electric potential, the other employs the direct current feedback circuit and two indifferent electrodes for the atrial stimulation and R-wave sensing. These methods have been proved to work perfectly with the ECG.

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For the purpose of blood-flow measurement within small sampling area, the pulsed Doppler system and M-sequence modulation Doppler system have been used. In the pulsed Doppler system, it is difficult to generate and process transmitted and received signals and to maintain a sufficient average power in the transmitted signals. On the other hand, in the M-sequence modulation system, unnecessary Doppler signals are not eliminated completely because of the auto-correlation property of the M-sequence. The unnecessary signals, therefore, cause decline in the sensitivity for detecting Doppler signals from a desired sampling area.
In this paper, new cross-correlation sequences are presented whose cross-correlation values are zero, except that one sequence with the width t_c of clock pulse and the period N is shifted by kNt_c and kNt_c+t_c/2 (k=0, ±1, ±2 ……) with respect to the other with the width t_c/2 of clock pulse and the petiod 2 N. Moreover, a new ultrasonic Doppler system using these sequences is described. With this proposed modulating method, unnecessary reflected signals can be eliminated completely.

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The bone conducted vowels were picked up by the vibration transducer of the acceleration type applied to the anatomical sites on the head (upper jaw, forehead and mastoid region). These signals were analysed by calculating their spectral envelopes under the method of maximum likelihood spectral estimation.
The spectral characteristics in low frequency range of these bone conducted vowels were similar to those which were recorded from the microphone at the position of 30 cm from the lips. As a result of investigating many spectral envelopes, an inclination towards attenuation of high frequency range was detected, and spectral peaks at the frequency of about 2 kHz were evident for the bone conducted Japanese vowels /e/ and /i/ picked up at the upper jaw.
It was proved experimentally that the existence of those spectral peaks in the bone conducted vowels at the upper jaw was dependent on the pathophysiological condition in the paranasal sinus.
From a point of view described here, it can be said that the bone conducted vowels may be applicable to clinical evaluation for some cystic lesions and solid tumors of the upper jaw.

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The pressure-volume relations of the left ventricle were derived at different geometries by using a homogeneous and isotropic spherical shell model based on the large deformation theory. In this study, the mechanical behavior of the unit myocardium was assumed to be equal to all the hearts.
The results obtained were as follows : 1. At the same undeformed left ventricular volume, changes in the left ventricular weight exerted only a slight influence on the ventricular pressure-volume relation. 2. However, an increase in the undeformed left ventricular volume caused a marked change in the left ventricular pressure-volume relation. Thus the rise in the left ventricular compliance was obvious. But the relation between the ratio of the actual volume change of the left ventricle to undeformed volume and left ventricular pressure showed no apparent differences. 3. Moreover, the relation between the ratio of the left ventricular volume to weight and left ventricular pressure could be determined by the undeformed left ventricular geometry, namely the ratio of the left ventricular undeformed volume to weight.

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The electrical properties of blood are of practical interest in medical and biological engineering, such as in impedance plethysmography and ECG, because the impedance of blood is less than that of all other living tissues.
It is well-known that when blood flows, its impedance changes from its resting, value. The change in the resistivity of flowing blood is principally due to three factors-the axial accumulation, the orientation of red cells and the deformation of red cells. These phenomena occur simultaneously.
In this paper, the effects of these three phenomena upon the blood resistivity are theoretically and experimentally discussed. The resistivity of blood and its changes have been measured. The reflected light from blood was simultaneously detected in order to discuss the phenomenon because the light is mainly reflected from the red cells and is affected by the orientation of the red cells.
Not all of the red cells are oriented along the flow line of the blood. They always rotate. However, the resistivity of blood changes with the change of flow because the rotating velocity depends on the angle between the red cell and the flow line. Therefore, it seems that a part of red cells is equivalently oriented along the flow line of the blood.
Only about 50% of the red cells are equivalently oriented in high shear flow (1 000 s^-1). In the living body, the maximum shear rate is considered to be about 100 s^-1. In this case, about 20 %-30% of the red cells are oriented. And relative change in resistance due to the orientation is about 10%.
The thickness of the plasma layer in actual blood is considered to be about 5 μm. Therefore, only when the physical properties of the blood in capillaries is discussed, this phenomenon becomes highly important.
From the experimental and theoretical results, it is assumed that the change of resistivity in the flowing blood depends mainly upon the orientation of the red cells.

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