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Biomedical subjects

K Yamakoshi

Publications and source records attributed to K Yamakoshi.

At least 19 recordsLinked to original sources
PubMed2005

Unconstrained detection of respiration rhythm and pulse rate with one under-pillow sensor during sleep.

A completely non-invasive and unconstrained method is proposed to detect respiration rhythm and pulse rate during sleep. By employing wavelet transformation (WT), waveforms corresponding to the respiration rhythm and pulse rate can be extracted from a pulsatile pressure signal acquired by a pressure sensor under a pillow. The respiration rhythm was obtained by an upward zero-crossing point detection algorithm from the respiration-related waveform reconstructed from the WT 2(6) scale approximation, and the pulse rate was estimated by a peak point detection algorithm from the pulse-related waveform reconstructed from the WT 2(4) and 2(5) scale details. The finger photo-electric plethysmogram (FPP) and nasal thermistor signals were recorded simultaneously as reference signals. The reference pulse rate and respiration rhythm were detected with the peak and upward zero-crossing point detection algorithm. This method was verified using about 24 h of data collected from 13 healthy subjects. The results showed that, compared with the reference data, the average error rates were 3.03% false negative and 1.47% false positive for pulse rate detection in the extracted pulse waveform. Similarly, 4.58% false negative and 3.07% false positive were obtained for respiration rhythm detection in the extracted respiration waveform. This study suggests that the proposed method is suitable, in sleep monitoring, for the diagnosis of sleep apnoea or sudden death syndrome.

Adult↗
PubMed2003

Reconstruction of a defect of the rotator cuff with polytetrafluoroethylene felt graft. Recovery of tensile strength and histocompatibility in an animal model.

We reconstructed defects in the infraspinatus tendon u sing polytetrafluoroethylene (PTFE) felt grafts in 31 beagle dogs and examined the mechanical responses and histocompatibility. Except for one infected specimen, all the reconstructed infraspinatus tendons healed. We examined eight specimens each immediately after surgery and at six and 12 weeks. The ultimate tensile strength of the reconstructed tendons was 60.84 N, 172.88 N, and 306.51 N immediately after surgery and at six and 12 weeks, respectively. The stiffness of the specimens at the PTFE felt-bone interface was 9.61 kN/m, 64.67 kN/m, and 135.09 kN/m immediately after surgery and at six and 12 weeks, respectively. Six tendons were examined histologically at three, six, 12 and 24 weeks. Histological analysis showed that there was ingrowth of fibrous tissue between the PTFE fibres. Foreign-body reactionswere found at the margin of the PTFE-bone interface between 12 and 24 weeks. The mechanical recovery and tissue affinity of PTFE felt to bone and to tendon support its use for reconstruction of the rotator cuff. The possible development of a foreign-body reaction should be borne in mind.

Animals↗
PubMed2001

Normalized pulse volume (NPV) derived photo-plethysmographically as a more valid measure of the finger vascular tone.

Normalized pulse volume (NPV) was advocated as a more valid measure for the assessment of finger vascular tone. Based on the optical model in the finger tip expressed by Lambert--Beer's law, NPV is expressed as Delta I(a)/I. Here, Delta I(a) is the intensity of pulsatile component superimposed on the transmitted light (I). Theoretically, NPV seems to be superior to the conventional pulse volume (PV; corresponding to Delta I(a)). Firstly, NPV is in direct proportion to Delta V(a), which is the pulsatile component of the arterial blood volume, in a more exact manner. Relatedly, NPV can be processed as if it is an absolute value. Secondly, the sensitivity of NPV during stressful stimulations is expected to be higher. These expectations were supported experimentally using 13 male students. Firstly, the correlation between cutaneous vascular resistance in the finger tip (CVR) and NPV was higher than that between CVR and PV among all the subjects, although there was not much difference between these correlations within each subject. Secondly, NPV decreased much more than PV during mental stress. Some limitations of the present study were addressed, including the point that certain factors can violate the direct proportional relationship of NPV and PV to Delta V(a).

Adult↗
PubMed2001

Restoration of immunocyte functions by thymosin alpha1 in cyclophosphamide-induced immunodeficient mice.

Thymosin alpha1 (Talpha1) is an oligopeptide hormone originally isolated from the thymus gland, and has been reported to have stimulating effects on the differentiation of T cells and NK cells. These immunostimulating properties have been considered to be useful for improving immune disorders associated with various diseases including cancer, AIDS and hepatitis. Here, we characterized immunostimulating properties of Talpha1 in experimental immunodeficiency of mice that was induced by the administration of cyclophosphamide (CY). Repeated injection of 30-300 microg/kg/day of Talpha1 after CY-treatment significantly accelerated the restoration of the reduced number of CD4+CD8+ T cells in the thymus. Talpha1 administration was effective in restoring the suppressed activities of helper T cells and cytotoxic T cells in CY-treated mice. Talpha1 also had stimulating effects on reduced activity of lymphokine-activated killer cells in CY-treated mice. These results indicate that Talpha1 is stimulatory for both humoral and cellular immune responses, thus providing the immunological basis for the clinical benefit of this compound.

Animals↗
PubMed2000

A portable instrument for non-invasive monitoring of beat-by-beat cardiovascular haemodynamic parameters based on the volume-compensation and electrical-admittance method.

A new, portable instrument has been developed for simultaneous monitoring of blood pressure, cardiac output and other cardiovascular haemodynamic variables. The measurements are based on the volume-compensation method and the transthoracic electrical admittance method. The instrument is small and light and can be carried by the subject. The portable unit controls the measurement procedures, performs the blood pressure and cardiac output measurement, processes signals and stores almost 32,000 beats of time-series data in a fully automated manner. A conventional personal computer is used to initialize the measurement system, and to reproduce and evaluate the measurement data. The measurement system provides a means to evaluate in detail, without restriction, the subject's cardiovascular haemodynamic responses to daily physical activities as well as to various psycho-physiological stresses. The paper describes a new, portable, cardiovascular haemodynamic instrument and in-the-field test results. Twelve subjects are monitored for trials, 60-210 min, and fewer than 3% of the data in each trial are artifactual. Artefacts are due mainly to body movements.

Adult↗
PubMed2000

Beat-by-beat double-normalized pulse volume derived photoplethysmographically as a new quantitative index of finger vascular tone in humans.

Near-infrared finger photoplethysmograms were recorded and double-normalized pulse volumes (DNPV = DeltaV(b)/V(b); V(b) = total blood volume in the fingertip, DeltaV(b) = pulsatile component of V(b)) were calculated in ten subjects during, immersion of the contralateral hand in water at three different temperatures (44 degrees C, 22 degrees C, 11 degrees C). The DNPV from the left finger was compared beat-by-beat with cutaneous vascular resistance (CVR) derived by dividing mean blood pressure of the left third finger by cutaneous blood flow of the left fourth finger. The correlations overall at the three temperatures between log DNPV(LF) and log CVR(LF) (LF, low frequency component of DNPV and CVR) ranged from -0.89 to -0.96 among the subjects. After adjusting for a maximal extension of the vascular wall (DNPV(max)), the correlations became stronger. It was concluded that DNPV was a reliable and valid indicator of vascular tone in the finger.

Adult↗
PubMed2000

Unconstrained physiological monotoring in daily living for health care.

This paper deals with the recent development of two types of non-invasive physiological monitoring systems for possible application in an unconstrained manner to normal subjects for health care as well as to patients and/or outpatients with disorders or with life support systems (artificial organs and organ transplantations). One is an ambulatory monitoring system which allows automatic acquisition of blood pressure, cardiac output and other cardiovascular hemodynamic parameters on a beat-by-beat basis using the volume-compensation and transthoracic electrical admittance method. The other is a home monitoring system installed in a lavatory which can measure body and excreta weight together with the ballistocardiogram as an index of cardiac ejecting function in an unaware fashion without attachment of any sensors to the subject's body and without special operations for measurement during toilet use. Outlines of these two systems and monitoring results of laboratory and field testings are presented, and these suggest that the ambulatory and non-conscious physiological monitoring techniques described herein appear promising as a valuable and helpful means for use in research as well as in the practical field of health monitoring at home during daily living.

Activities of Daily Living↗
PubMed2000

Effects of periosteum wrapped around tendon in a bone tunnel: A biomechanical and histological study in rabbits.

The present study demonstrated the effects of periosteal autograft on tendon-to-bone healing in the rabbits. In 20 Japanese white rabbits, proximal end of the long digital extensor tendon that was wrapped around by a periosteum was transplanted into a drill hole in the proximal tibial metaphysis. A fresh periosteum was used in the left tibia and a frozen periosteum was used in the right tibia. Six specimens were harvested at each 2, 4, and 6 weeks postoperatively. Radiological features showed progressive remodeling of trabecular bone surrounding the implanted tendon. This remodeling in fresh periosteal graft was earlier than that in frozen graft. Generally, the pull-out strength of the transplanted tendons with a fresh or frozen periosteum increased progressively according to the length of the healing periods. The strength was significantly greater in a fresh periosteal graft than that in a frozen graft at 4 weeks postoperatively. In histological analysis, a 4-week specimen with the fresh periosteal graft showed fibrocartilage formation in the bone tendon interface, whereas the specimens with the frozen graft demonstrated simple approximation of oriented fibrous tissue. In conclusion, the fresh periosteal autograft produced the premature form of fibrocartilagenous attachment in a bone tunnel and provided good mechanical strength.

Animals↗
PubMed1998

Measurement of mechanical characteristics of tibial periosteum and evaluation of local differences.

Stress-strain relationships of bovine tibial periosteum, harvested from anterior, medial, lateral, and posterior aspects of tibia, were successfully measured using a newly developed experimental system. Results showed a curvilinear stress-strain pattern having three regions, i.e., toe, almost linear, and rupture regions, which resembled those of biological soft tissues like ligaments, skin, etc. Tensile moduli in the toe region (Ee) and in the linear region (Ec) were obtained by linear regressional analyses. These values and the tensile strength (sigma t) showed clear local differences. The values of Ee, Ec, and sigma t in the longitudinal direction in the metaphyseal regions where ligaments or connective tissues attach were approximately two times larger than those in the diaphysis, where muscles or connective tissues attach. However, these properties in the metaphyseal and diaphyseal regions with muscle attachments were almost the same. In the transverse direction, these properties in the anterior proximal metaphysis were approximately two times larger than those in the diaphysis and in the distal metaphysis. In the other regions, these properties appeared not to be significantly different. These results clearly demonstrate that the mechanical properties of periosteum are strongly influenced by the ligament and muscle attachments.

Animals↗
PubMed1998

Fully automated health monitoring at home.

The aim of this study was to provide adequate home health monitoring for the elderly at home using fully automated signal measurement with personal identification to support daily health care and to improve quality of life. We attempted to develop a home health monitoring system that did not provide any restrictions during sleep, bathing and excretion. A new room including bath and toilet was constructed. The system consisted of monitoring devices and a computer terminal for collecting data. The data were automatically obtained from monitoring devices situated at the bed, bath and toilet and were transferred to a data terminal and stored for further analysis. Where subjects live with their spouse or family, personal identification is required to store data individually. For the bathtub data, personal identification was performed using ECG data. Sampled data were reduced by wavelet transform and distinguished by a neural network. The data acquisition system is now underway and data are being extensively collected.

Aged↗
PubMed1997

New technique for time series analysis combining the maximum entropy method and non-linear least squares method: its value in heart rate variability analysis.

A new technique for time series analysis, which is a combination of the maximum entropy method (MEM) for spectral analysis and the non-linear least squares method (LSM) for fitting analysis, is described. In this technique, the MEM power spectral density (MEMPSD) is calculated using a very large lag that could diminish the lag dependence of dominant periods estimated by the MEM analysis. The validity of this large lag is confirmed by the LSM, given that the ten dominant MEM periods are known quantities. To validate the MEM plus LSM technique, it is compared with autoregressive (AR) modelling, by analysing heart rate variability under pharmacological interventions (phenylephrine and trinitroglycerine), using 16 young males. The results indicate that the MEMPSD, when compared with the ARPSD, has numerous periods that could reproduce the original time series much more accurately, as revealed by the LSM analysis. However, both the low- and high-frequency powers with MEMPSD and ARPSDs shift in the expected directions in accordance with the pharmacological effects on the cardiovascular system. The implications of these results are discussed from the theoretical and practical standpoints of the MEM plus LSM technique, compared with AR modelling.

Adolescent↗
PubMed1996

Ambulatory instrument for monitoring indirect beat-to-beat blood pressure in superficial temporal artery using volume-compensation method.

A portable instrument, based on a volume-compensation technique, is designed for ambulatory monitoring of indirect beat-to-beat blood pressure (BP) in the superficial temporal artery. The instrument consists of a small disc-type cuff and a portable unit carried by the subject. Several components are integrated in the cuff for applying counter-pressure to the artery, i.e. a reflectance-type photo-plethysmographic sensor for arterial volume detection, a pressure sensor for cuff pressure Pc measurement and a nozzle flapper-type- electro-pneumatic convertor for controlling Pc. The portable unit includes volume servo control circuitry and a microprocessor-based signal-processing and recording unit. This automatically performs all the necessary measurement procedures and stores into a memory IC element the processed systolic, mean and diastolic blood pressure data, together with pulse intervals on a beat-to-beat basis from the servo-controlled Pc (indirectly measured BP waveform). With this instrument, momentary changes in BP during ambulatory situations such as bicycle ergometer exercise and daily activities including motorway driving are successfully recorded. From the results of simultaneous measurement of the subject's posture changes, the effect of posture change on blood pressure, e.g. baroreceptor-cardiac reflex, is also clearly demonstrated.

Blood Pressure Monitoring, Ambulatory↗
PubMed1994

Electrical admittance cuff for noninvasive and simultaneous measurement of haematocrit, arterial pressure and elasticity using volume-oscillometric method.

An improved technique based on the electrical admittance cuff was designed for the non-invasive measurement of haematocrit (Hct), together with blood pressure (BP) and arterial elasticity represented as volume elastic modulus (Ev), in human fingers. This device is made of a rigid annular chamber installed with a surrounding thin-walled tube (cuff), which is filled with electrolyte solution. A tetrapolar method is used to detect the admittance signals, both in the solution and in a finger segment placed through the cuff. With this device, it is theoretically shown that the resistivity of blood flowing into the segment is equal to that of the solution multiplied by the ratio of the admittance variation in the solution to that in the segment. Thus, the blood resistivity and therefore Hct can be non-invasively determined from the electrolyte resistivity and these two admittance variations. On the other hand, BP and Ev are also simultaneously measured from the admittance signals following the gradual change of the chamber pressure based on the volume-oscillometric method. Experiments were successfully made in 14 subjects, showing that the indirect Hct values agreed well with the direct values obtained from sampled blood and that this simple technique was significant for the non-invasive ad simultaneous measurement of these physiological variables.

Adult↗
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↗