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Biomedical subjects

K Yamakoshi

Publications and source records attributed to K Yamakoshi.

At least 19 recordsLinked to original sources
PubMed1992

Entrainment of respiratory rhythm to respiratory oscillations of arterial PCO2 in vagotomized dogs.

The aim of this study was to demonstrate that the medullary respiratory rhythm generator is capable of entraining to respiratory oscillations of arterial PCO2 (CO2 oscillations). We used 10 anesthetized, paralyzed, vagotomized, and mechanically ventilated dogs. First, rate of mechanical ventilation was manually adjusted so that it matched the dog's spontaneous respiratory rate, which established a constant phase relationship between the mechanical ventilation and the burst of phrenic neurogram (initial phase). Then this phase relationship was temporally disturbed by a brief electrical stimulation of the superior laryngeal nerve (SLN). In the control group, the initial phase and the steady-state phase relationship after SLN stimulation were randomly distributed within the phase plane, implying no interaction between the respiratory center and mechanical ventilation. In contrast, when CO2 output from the lung was increased 2.6-fold above the control level by venous CO2 loading, the initial phase and the steady-state phase after SLN stimulation were locked in such a way that the onset of the burst of phrenic neurogram coincided with the peak of CO2 oscillations. This was not demonstrated when the dog was made hyperoxic. We therefore conclude that the respiratory center could entrain to phasic chemical afferent inputs originating from CO2 oscillations, provided they are considerably amplified.

Animals↗
PubMed1991

Radiographic findings of degeneration in cervical spines of middle-aged soccer players.

Twelve amateur veteran soccer players (average age 40.1 +/- 5.4 years), who began playing in their teens and who were admitted with symptoms most likely to be related to cervical spondylosis, were examined by cervical radiography. Abnormal radiographic findings included: calcification of anterior longitudinal ligament (25%), anterior (75%) and posterior vertebral spurs (75%), ossicle between spinous processes (75%), calcification of nuchal ligament (Barsony) (58%), ossicle on spinous process (25%), and bony spur of Luschka's joints (83%). It was shown in the stress distribution by finite element method analysis that the stress in heading the ball was applied mainly to the lower parts of the cervical spine. The results of this analysis also corresponded well with some of the radiographic findings.

Adult↗
PubMed1991

Ambulatory monitoring of indirect beat-to-beat arterial pressure in human fingers by a volume-compensation method.

Using a volume-compensation technique, a portable device has been designed for the indirect measurement of beat-to-beat arterial pressure and its waveforms in the basal phalanx of fingers of ambulatory subjects. The device consists of (1) a transmission infra-red photoelectric plethysmograph (TIPP) to detect the variation of arterial volume, (2) a pneumatic cuff with an actuator, (3) a servosystem to control the cuff pressure, and (4) a stereo cassette tape recorder. Arterial pressure was determined from the cuff pressure which was controlled by the servosystem so as to maintain the arterial volume constant at the 'vascular unloading' state. This device is equipped with a compensator for any hydrostatic pressure difference between the heart and finger. Thus, the blood pressure at heart level can be obtained for any finger height. The total weight of the device was 1.6 kg. Blood pressure changes during walking, jogging, jumping, and exercises such as side-stepping, Master's two-step test and car driving, have been successfully recorded.

Ambulatory Care↗
PubMed1991

Pressure-volume relationships of finger arteries in healthy subjects and patients with coronary atherosclerosis measured non-invasively by photoelectric plethysmography.

Knowledge of the mechanical properties of the small arteries is important for understanding physiological and pathophysiological conditions in the human peripheral circulation. We have recently developed a new method for the noninvasive measurement of arterial elastic properties in human fingers using photoelectric plethysmography. In this study, the pressure-volume relationship, an index for expressing arterial elasticity, was measured by this method in the finger arteries of 91 healthy subjects and 102 patients with coronary artery disease. Aging effects on the elastic properties of finger arteries were examined in healthy subjects classified into three groups: under 30, 31-49, and over 50 years of age. The pressure-volume curve shifted downward with increase in age, indicating that the elasticity of finger arteries decreased with age. Patients with 75% or greater coronary stenosis, as compared with age-matched healthy subjects, showed distinctly lower elasticity of finger arteries. As the number of diseased coronary arteries increased, the elasticity of finger arteries tended to decrease steadily. The elasticity of finger arteries decreased in coronary disease patients with hypertension much more than in those without hypertension. These results suggest that age-related changes in arterial elasticity can occur in peripheral small arteries, and that peripheral arteries in patients with coronary atherosclerosis are less elastic than those in healthy subjects.

Adult↗
PubMed1991

Simultaneous measurement of changes in length of the cruciate ligaments during knee motion.

The changes in length of electrolyte-in-rubber strain-gauge transducers implanted along the fibers of the anterior (ACL) and posterior (PCL) cruciate ligaments of the human anatomic specimen knees were measured simultaneously and continuously during knee motion. In unconstrained flexion and extension of the knee, all transducers in the ACL showed the maximum shortening peak at about 30 degrees flexion. After this, the length of the transducers in the anterior bundle increased, whereas those in the posterior bundle remained shortened. Transducers in the anterior and posterior bundles of the PCL, on the other hand, showed maximum lengthening peaks at approximately 50 degrees and 0 degrees flexion, respectively. The middle bundle of the PCL showed a smaller change. When simulated quadriceps forces were applied, the transducers in the ACL lengthened and those in the PCL shortened. At more than 90 degrees, however, the changes in length decreased. After cutting the ACL, the quadriceps force increased the shortening of the PCL.

Adult↗
PubMed1990

Non-invasive and simultaneous cardiovascular measurements using plethysmography techniques.

New non-invasive multifunctional methods have been proposed for the simultaneous measurements of more than two cardiovascular hemodynamic parameters such as peripheral and central blood flow, arterial and venous pressure, peripheral flow resistance, arterial and venous elasticity, hematocrit, blood oxygenation, etc. A proper combination of one or two of the recently developed sphygmomanometries called the 'volume oscillometric method' and the 'volume compensation method' with photoelectric plethysmography, and blood flowmetry with electrical admittance plethysmography provides successful measurement of these cardiovascular parameters. This paper discusses the measurement principles, including methodologies, and evaluates the accuracy and practicability of each method. Preliminary descriptions of newly designed instruments based on these methods together with a few examples of measured data are also presented. The results obtained show that the proposed non-invasive and simultaneous physiological measurements appear promising for use not only in basic research laboratories, but also in clinical practice including health screening and testing.

Adult↗
PubMed1989

Electric impedance cuff for the indirect measurement of blood pressure and volume elastic modulus in human limb and finger arteries.

A new plethysmograph, the electric impedance cuff, was designed for the indirect measurement of blood pressure, volume elastic modulus Ev and compliance Ca in human limb arteries. This comprises a compression chamber filled with electrolyte solution and a tetrapolar electric impedance plethysmograph whose electrodes are placed inside the chamber; the former for controlling transmural arterial pressure Pt, and the latter for detecting total limb volume Vo, mean arterial volume Va and its variation delta Va. Systolic and mean arterial pressure in the upper arms, forearms and fingers were measured by detecting pulsatile impedance variation during the gradual (3-5 mm Hg per heart beat) increase (or decrease) in chamber pressure by the volume oscillometric technique. Diastolic and pulse pressure delta P were calculated from these pressure values. Compliance Ca = delta V/delta P and volume elastic modulus Ev = delta P/(delta Va/Va) were recorded at various Pt levels, controlled by the compression pressure. Although this is a kind of impedance plethysmograph, the volume change in a limb segment can be detected by this method without passing electric current through the limb.

Adult↗
PubMed1989

Vibration technique for indirect measurement of diastolic arterial pressure in human fingers.

Diastolic pressure Pd was indirectly measured by vibrating a finger artery with a 10 Hz sinusoidal pressure variation during a gradual increase (or decrease) in occlusive cuff pressure Pc. Pulsatile arterial volume changes on which sinusoidal variations are superimposed were detected by a transmitted infra-red photoelectric plethysmograph (TIPP). It is known that volume change in an artery shows a maximum amplitude at the transmural pressure Pt level equal to 0 mm Hg due to the nonlinear viscoelastic properties of the arterial wall. For the same reason, the amplitude of the sinusoidal volume variation reached its maximum at the end-diastolic phase, when Pc was controlled to be exactly equal to Pd. The indirect Pd values determined from Pc were compared with those simultaneously measured by a direct method in rabbit forelegs and by the volume-compensation method in human fingers. Using the principle of the volume oscillometric method systolic and mean pressures were also determined by this system.

Adult↗
PubMed1989

[Measurement of changes in distance between the femoral and the tibial drill holes for the anterior cruciate ligament reconstruction].

We have developed an experimental system in which a new Gallium-Indium containing transducer can continuously measure the changes of separation distances between the femoral and tibial points. The measurements provides information for the attachment location in the anterior cruciate ligament (ACL) reconstruction and used for various combinations of extra-articular and intra-articular methods. At the first experiment, the distance between each pair of points at the level of the capsule for fifteen combinations during simple flexion-extension knee motion were measured on six cadaveric knees. At the next experiment, in an ACL-deficient knee the distances of ten combinations in the intra-articular method were measured. These results indicated that for an isometric placement the combination of the center of tibial insertion and the postero-proximal of the femoral origin of the ACL appeared to furnish a better location for intraarticular reconstruction. No combination was recommended for extraarticular reconstruction.

Biomechanical Phenomena↗
PubMed1988

Current developments in non-invasive measurement of arterial blood pressure.

Two new types of non-invasive method for measuring arterial blood pressure recently developed by us are reviewed. Both of the methods are based on the characteristics of the pressure-volume relationship in the artery. One is the volume-oscillometric method; and the other is the volume-compensation method, based on the vascular unloading principle. Both methods employ photoelectric plethysmography for detection of arterial volume changes in the biological segment. The volume-oscillometric method can measure systolic and mean arterial pressure, and is applicable to long-term ambulatory monitoring. The volume-compensation method allows the beat-by-beat measurement of systolic and diastolic pressure and the recording of the pressure waveform continuously and non-invasively. This paper discusses the measurement principle and evaluates the accuracy of each method as compared with direct measurements. Preliminary descriptions of newly designed instruments based on these two methods, and a few examples of the indirect pressure recordings, are also described. The results obtained show that the non-invasive methods for measuring arterial pressure presented here appear promising for use not only in physiological studies, but also in clinical practice and research laboratories.

Animals↗
PubMed1988

Hypertensive episodes and circadian fluctuations of blood pressure in patients with phaeochromocytoma: studies by long-term blood pressure monitoring based on a volume-oscillometric method.

A new portable device for the indirect measurement of arterial blood pressure was successfully applied to detect paroxysmal hypertension and circadian fluctuation of blood pressure in patients with phaeochromocytoma. The device utilizes the volume-oscillometric technique, it is equipped with a microprocessor and allows long-term automatic monitoring of indirect blood pressure in the human finger. Compared with conventional fully automated portable devices of the arm-cuff type, our current equipment is lighter, less noisy, and causes less discomfort. With this device repeated measurements can be made without causing stress or discomfort, and without disturbing sleep. The arterial pressure measurement obtained using this device was reliable and reproducible. In some patients certain symptoms, possibly due to phaeochromocytoma, had been observed for several years before the study, although hypertension had not been identified. While these patients had consistently high circulating catecholamine levels, nocturnal falls in blood pressure were clearly documented. This suggests that plasma catecholamines released from the phaeochromocytoma, though excessive, may be of less physiological importance than other regulatory mechanisms concerned with circadian fluctuation of blood pressure, e.g. the sympathetic nervous system and/or hypothalamo-pituitary-adrenal system. This new device has proved to be a reliable means of monitoring long-term blood pressure and is useful in the diagnosis of paroxysmal hypertension in patients with phaeochromocytoma.

Adolescent↗
PubMed1987

Noninvasive measurement of arterial blood pressure and elastic properties using photoelectric plethysmography technique.

The objective of this paper is to review our developed method for measuring noninvasively the arterial blood pressure as well as the mechanical properties of the vascular system in a thin portion of the biological segment such as human fingers or small animal extremities like rat tails and rabbit forelegs. This measurement is based on a principle called the 'volume-oscillometric method'. During the gradual change in cuff pressure, the amplitude of consecutive arterial volume pulsations associated with pulse pressure shows change characteristically due to the nonlinearity of arterial pressure-volume(P-V) relation. Arterial pressure can be accurately determined by detecting this characteristic change in the amplitude, while the arterial elastic properties such as P-V relationship and volume elastic modulus can be noninvasively obtained as a function of arterial transmural pressure, provided that the arterial volume changes are quantitatively determined during this pressure measurement. The validity and accuracy of this pressure and elasticity measurement with photoelectric plethysmography technique for detecting arterial volume changes are clearly demonstrated on the in vitro and in vivo experiments. Considering the simplicity and practicability of this measurement using the photoelectric plethysmography, we present a new portable instrument for the long-term ambulatory monitoring of indirect arterial pressure and a handy fully-automatic instrument for the noninvasive measurement of arterial elastic properties, and a few examples obtained by each instrument are also described.

Animals↗
PubMed1987

A compact centrifugal blood pump for extracorporeal circulation: design and performance.

A new compact centrifugal blood pump driven by a miniature DC servomotor has been designed for use for short-term extra corporeal and cardiac-assisted circulation. The impeller of the pump was connected directly to the motor by using a simple-gear coupling. The shaft for the impeller was sealed from blood by both a V-ring and a seal bearing. Either pulsatile or nonpusatile flow was produced by controlling the current supply to the motor. The pump characteristics and the degree of hemolysis were evaluated with regard to the configuration of the impeller with a 38-mm outer diameter in vitro tests; the impeller having the blade angles at the inlet of 20 deg and at the outlet of 50 deg was the most appropriate as a blood pump. The performance in an operation, hemolysis and thrombus formation in the pump were assessed by a left ventricular bypass experiment in dogs. It was suggested by this study that this prototype pump appears promising for use not only in animal experiments but also in clinical application.

Animals↗
PubMed1987

Neurogenic factors affecting ventilatory and circulatory responses to static and dynamic exercise in man.

The possible influence of neurogenic factors on respiratory and circulatory responses to continuous static (CSE), rhythmic static (RSE), and dynamic (DE) exercises was studied in 15 healthy young men. Ventilation (VE), oxygen uptake (VO2), cardiac output (Q), and blood pressure (BP) were measured during the steady-state of the exercise. For a given VO2, VE, and respiratory frequency (f) enhanced significantly with increasing frequency of RSE, and for the same frequency, the responses of these variables to RSE were significantly higher than those for DE. Although a similar trend was observed in heart rate (HR) and Q responses to exercises, it was not as strong as for ventilatory responses. These results lead to the conclusion that ventilation and circulation during exercise may be influenced by some neurogenic factors mediated either centrally or peripherally.

Adolescent↗
PubMed1987

A finger volume-oscillometric device for monitoring ambulatory blood pressure: laboratory and clinical evaluations.

A new portable device for the indirect measurement of ambulatory blood pressure in the finger was successfully applied to normotensive and hypertensive subjects in and outside a ward setting. The device uses the volume-oscillometric technique and, equipped with a microprocessor, permits long-term ambulatory monitoring of indirect systolic and mean blood pressure at desired intervals (once every 1-10 min). Systolic and mean blood pressures obtained by this method were well correlated with those measured by the direct (Oxford) and arm-cuff methods. Systolic and diastolic blood pressure obtained by the volume-oscillometric device were almost identical with those recorded by an arm-cuff. Systolic blood pressure obtained by the volume oscillometric method was, however, significantly lower than that measured by the direct method. The new device has also been used to measure blood pressure during treadmill exercise and ice-water immersion. Mean values of blood pressure and the SD of these averaged for 24 hours, or for every hour, were reproducible when the measurements were repeated under the same condition. The present device is portable, causes minimal noise, can detect rapid change in blood pressure and causes less discomfort when compared to the conventional arm-cuff method. Regular measurements can be made with minimal sleep disturbance. This fully automatic volume-oscillometric device allows reliable 24-hour monitoring of ambulatory blood pressure not only in but also outside a ward setting, and as such is useful for studies of hypertension.

Ambulatory Care↗
PubMed1986

Step response analyses of the cardiovascular system and their application to the measurement of systemic and pulmonary vein compliances.

A theoretical analysis of the step response in the closed cardiovascular system induced by a sudden shift of the right cardiac output curve predicted that if the relations of the right heart output (COr) and the total systemic capillary flow (CFs) to the systemic venous pressure (Psv) are linear, then the time course of Psv change will become monoexponential with a time constant T given by T = Csv/(Gr + Gs), where Csv is the systemic vein compliance and Gr and Gs are the conductances of the transient COr-Psv and CFs-Psv relationships. A similar prediction was obtained for the time constant T of the pulmonary vein pressure (Ppv) response to the step change in the left cardiac output (COl) curve, pulmonary vein compliance (Cpv) and the conductances of the COl curve, and the pulmonary capillary flow (CFp) curve against Ppv. The actual Psv or Ppv changes following sudden alteration of the COr or COl curve by inflation and deflation of the balloon in the right or left atrium revealed monoexponential time courses. Semilogarithmic plots of the transient vein pressure changes yielded correlation coefficients of -0.995 +/- 0.006 (means +/- SD) in 11 curves for Psv and 0.977 +/- 0.017 in 16 curves for Ppv (P less than 0.01). The assumed linearity of dynamic COr and COl curves was confirmed by beat by beat COr-Psv and COl-Ppv relationships during the step responses, except for the first few beats immediately after the balloon maneuver. The linearity of the dynamic CFs curve was examined by measuring CFs with a double-step balloon maneuver so as to cause rapid equilibrium between COr and CFs at varied moments of the transient process. The correlation coefficient between CFs and Psv thus obtained was 0.98 +/- 0.04 (P less than 0.01). A similar linearity of the dynamic CFp-Ppv relationship was suggested from their steady-state curves. The values of Csv calculated from the experimental data were 1.70 +/- 0.12 ml/mmHg/kg body wt in 11 curves and those of Cpv were 0.13 +/- 0.03 ml/mmHg/kg in 15 curves. These results are mostly consistent with those previously reported.

Animals↗