Development of a new aortoscope system for the use of endovascular intervention

"Balloon aortoscopy" is a technique for viewing inner wall of aorta and used in clinics. By this method, endoluminal aortic surface could be clearly monitored, however, during this period, the aortic blood flow is blocked off by the inflated balloon. To solve this clinical problem, we have been developing a prototype aortoscope system without blocking off aortic flow aiming for the use of an assistive technique for endovascular interventions such as stent-graft placement for aortic aneurysm and have been evaluating through in vitro and in vivo tests. The technique introduced for this purpose was the use of intermittent and instantaneous saline jet controlled by a high-speed electromagnetic valve synchronized to heart beat (diastolic phase). In the previous study, we designed an endoscope with two channels (one for saline discharge and the other for forceps insertion), and confirmed the validity of this method by in vitro and in vivo tests. Based on these findings, in this study, we have newly designed a conventional and low price endoscope system aiming for wide clinical use. From the results of in vitro tests using a mock circulation system, it was confirmed that the newly designed system was capable of visualizing a target installed on an inner surface of the mock system suggesting an availability of the system for an aortoscope without blocking off aortic flow.

Evaluation of a newly designed endoscope for observing inner wall of large arteries for the use of endovascular intervention

A prototype endoscope for observing inner wall of large arteries was specially designed and evaluated through in vitro and in vivo tests. The purpose of this endoscope is to visualize the inner wall of large arteries, e.g., an aorta, without blocking off the blood stream aiming for the use of an assistive technique for endovascular interventions such as stent-graft placement for aortic aneurysm. The technique newly introduced for this purpose was the use of intermittent high-pressure saline jet synchronized to heart beat (diastolic phase). In the previous studies using commercially available bronchoscopes, we confirmed the validity of the system utilizing this technique [1, 2]. Based on these findings, in this study, we have specially designed a new endoscope with two channels, one for saline discharge and the other for forceps, and evaluated its performance through in vitro and in vivo tests. From the results of in vitro tests using a mock circulation system, it was confirmed that the newly designed endoscope was capable of visualizing a target installed on an inner surface of the mock system. Also confirmed through in vivo tests using swine was that we could observe bifurcation in descending aorta, e.g., left renal artery, without stopping off the blood stream.

A new non-invasive method for measuring blood glucose using instantaneous differential near infrared spectrophotometry

We describe further development of a novel method for non-invasive measurement of blood glucose concentration (BGL), named Pulse Glucometry, based on differential near infrared spectrophotometry. Sequential temporal differences of infrared transmittance spectra from the radiation intensity (I(lambda)) emerging from a fingertip containing an arterial pulse component (DeltaI(lambda)) are analysed. To perform the measurements we developed a new high-speed spectrophotometer, covering the wavelength range from 900 to 1700 nm, scanning at a maximum spectral rate of 1800 spectra/s, with a minimum exposure time of 20 micros. Spectra related only to the pulsatile blood component are derived, thus minimising influences of basal components such as resting blood volume, skin, muscle and bone. We have now improved the performance of the spectrophotometer and in the present paper we describe new in vivo measurements carried out in 23 healthy volunteers undergoing glucose tolerance tests. Blood samples were collected from the cephalic vein simultaneously with radiation intensity measurements in the fingertip every 10 min before and after oral administration of glucose solution for 120 min. BGL values were then predicted using a PLS calibration model and compared with blood values determined by colorimetric assay. The precision and accuracy of the non-invasive determinations are encouraging.

A preliminary study on driver's stress index using a new method based on differential skin temperature measurement

Prolonged periods of driving in monotonous situations may lower a driver's activation state as well as increasing their stress level due to the compulsion to maintain safe driving, which may result in an increased risk of a traffic accident. There is therefore an opportunity for technological assessment of driver physiological status to be applied in-car, hopefully reducing the incidence of potentially dangerous situations. As part of our long-term aim to develop such a system, we describe here the investigation of differential skin temperature measurement as a possible marker of a driver's stress level. 10 healthy male subjects were studied, under environment-controlled conditions, whilst being subjected to simulated monotonous travel at constant speed on a test-course. We acquired measurements of relevant physiological variables, including truncal and peripheral skin temperatures (T(s)), beat-by-beat blood pressure (BP), cardiac output (CO), total peripheral resistance (TPR), and normalized pulse volume (NPV) used as an indicator of local peripheral vascular tone. We then investigated the driver's reactivity in terms of cardiovascular haemodynamics and skin temperatures. We found that the simulated monotonous driving produced a gradual drop in peripheral T(s) following the driving stress, which, through interpretation of the TPR and NPV recordings, could be explained by peripheral sympathetic activation. On the other hand, the truncal T(s) was not influenced by the stress. These findings lead us to suggest that truncal-peripheral differential T(s) might be used as a possible index indicative of the driver's stress.

Hemodynamic responses during simulated automobile driving in a monotonous situation

Long hours of automobile driving under monotonous situations may cause the lowering of what we term a driver's activation state (DAS) or in other words the production of drowsiness, resulting in an increased risk of a traffic accident. There is therefore a need to create a newly advanced system focused on the DAS in-car, hopefully thus avoiding potentially dangerous situations. In order to develop such a system as a final goal, we have firstly set out to acquire such cardiovascular variables as beat-by-beat blood pressure (BP), RR interval from ECG and normalized pulse volume (NPV) used as a peripheral vascular tone of alpha-adrenergic sympathetic activity, during presentation to the driver of a screen movie simulating monotonous travel at constant speed on a test-course. Subsequently, we have investigated the reactivity in terms of the driver's cardiovascular hemodynamics. Through the successful monitoring of cardiovascular parameters during the movie presentation obtained in 11 healthy male subjects, the following results were obtained: The monotonous driving produces a statistically significant gradual rise in BP following drowsiness, which could be explained by enhancement of sympathetic activity using a time-frequency analysis of BP and RR. This finding strongly indicates that continuous driving in such monotonous situations can make a driver considerably stressful and thus may cause a gradual increase in BP, and that this gradual BP increase may be used as a possible index relevant to the DAS. This finding was also confirmed by the analysis of NPV, suggesting that the gradual increase in BP during the monotonous driving would be rather caused by a regulation of peripheral vasomotor constriction.

Development of an ambulatory device for monitoring posture change and walking speed for use in rehabilitation

Monitoring of posture change in sagittal plane and walking speed is important for evaluate the effectiveness of rehabilitation program or brace. We have developed a wearable device for monitoring human activity. However, in the previous system, there still remain several drawbacks for practical use such as accuracy in angle measurement, cumbersome cable arrangements, and so on. In order to improve these practical drawbacks, a new sensor system was designed, and its availability was evaluated. The results demonstrated that the accuracy of this system showed superior to that of the previous, and this system appears to be a significant means for quantitative assessment of the patient's motion.

Feasibility study on driver's stress detection from differential skin temperature measurement

Prolonged monotonous driving may lower a driver's awareness level as well as increasing their stress level due to the compulsion to maintain safe driving, which may result in an increased risk of a traffic accident. There is therefore an opportunity for technological assessment of driver physiological status to be applied in-car, hopefully reducing the incidence of potentially dangerous situations. As part of our long-term aim to develop such a system, we describe here the investigation of differential skin temperature measurement as a possible marker of a driver's stress level. In this study, healthy male (n=18) & female (n=7) subjects were investigated under environment-controlled conditions, whilst being subjected to simulated monotonous travel at constant speed on a test-course. We acquired physiological variables, including facial skin temperature which consists of truncal and peripheral skin temperatures (Ts) using thermography, beat-by-beat blood pressure (BP), cardiac output (CO), total peripheral resistance (TPR), and normalized pulse volume (NPV) used as an indicator of local peripheral vascular tone. We then investigated the driver's reactivity in terms of skin temperatures with this background of cardiovascular haemodynamics. We found that the simulated monotonous driving produced a gradual drop in peripheral Ts following the driving stress, which, through interpretation of the TPR and NPV recordings, could be explained by peripheral sympathetic activation. On the other hand, the truncal Ts was not influenced by the stress. These findings lead us to suggest that truncal-peripheral differential Ts could be used as a possible index indicative of the driver's stress.

Development of a fully automated network system for long-term health-care monitoring at home

Daily monitoring of health condition at home is very important not only as an effective scheme for early diagnosis and treatment of cardiovascular and other diseases, but also for prevention and control of such diseases. From this point of view, we have developed a prototype room for fully automated monitoring of various vital signs. From the results of preliminary experiments using this room, it was confirmed that (1) ECG and respiration during bathing, (2) excretion weight and blood pressure, and (3) respiration and cardiac beat during sleep could be monitored with reasonable accuracy by the sensor system installed in bathtub, toilet and bed, respectively.

A new portable device for ambulatory monitoring of human posture and walking velocity using miniature accelerometers and gyroscope

Measurement of physical activity is one of the key subjects in the field of ambulatory cardiovascular monitoring using such as Holter ECG and so called "ambulatory blood pressure monitor (ABPM)". Rehabilitation and gerontology will also be another fields for the application of the activity monitor. From this point of view, we have developed a portable device for monitoring human posture and walking velocity in ambulatory subjects. In this paper are described, a new sensor system for this purpose using three accelerometers and one gyroscope, its availability for the accurate measurement of human posture and walking velocity, and results of preliminary study using a prototype system for ambulatory monitoring.

Development of a wearable device capable of monitoring human activity for use in rehabilitation and certification of eligibility for long-term care

The importance of human posture monitoring is well recognized in the field of rehabilitation, in order to evaluate quantitatively the effectiveness of rehabilitation by a physical therapist. The activity monitoring is also well recognized as being useful in the field of certification of eligibility for long-term care. Assessment of the actual physical condition of the applicant tends to be difficult when determine the level of need for long-term care. Taking these circumstances in consideration, we attempted to measure the activities of patients in rehabilitation using a wearable device for monitoring human activity. The results clearly demonstrated that detailed motion characteristics could be detected during standing up, walking and sitting up as angle changes between specific body segments and as trunk motion acceleration.

Assessing the Effectiveness of Increased F<inf>I</inf>O<inf>2</inf>for Enhancing Driver's Activation State Using Simulated Monotonous Driving

Lowering of what we term a driver's Activation State (AS) during monotonous driving conditions may increase the risk of an accident. To develop an in-car environment that allows active driving - "Biofee dforward System" - we have investigated the effects of applying a stimulus of increased inspired oxygen fraction (F<inf>I</inf>O<inf>2</inf>) supply on a driver's AS, using simulated monotonous driving. We used our previously substantiated index of As derived from beat-by-beat blood pressure (BP) response following an electrical stimulus. We have made physiological measurements including BP and found that the increased F<inf>I</inf>O<inf>2</inf>stimulus is effective in enhancing the AS. This finding was also confirmed in terms of the autonomic activity balance as well as the lengthening in time for active, safer, driving.

Physiological investigation of automobile driver's activation index using simulated monotonous driving

Monotonous automobile operation in our daily life may cause the lowering of what might be termed an activation state of the human body, resulting in an increased risk of an accident. We therefore propose to create a more suitable environment in-car so as to allow active operation of the vehicle, hopefully thus avoiding potentially dangerous situations during driving. In order to develop such an activation method as a final goal, we have firstly focused on the acquisition of physiological variables, including cardiovascular parameters, during presentation to the driver of a monotonous screen image, simulating autonomous travel of constant-speed on a motorway. Subsequently, we investigated the derivation of a driver's activation index. During the screen image presentation, a momentary electrical stimulation of about 1 second duration was involuntarily applied to a subject's shoulder to obtain a physiological response. We have successfully monitored various physiological variables during the image presentation, and results suggest that a peculiar pattern in the beat-by-beat change of blood pressure in response to the involuntary stimulus may be an appropriate, and feasible, index relevant to activation state.

Pulse glucometry: A new approach for noninvasive blood glucose measurement using instantaneous differential near-infrared spectrophotometry

We describe a new optical method for noninvasive blood glucose (BGL) measurement. Optical methods are confounded by basal optical properties of tissues, especially water and other biochemical species, and by the very small glucose signal. We address these problems by using fast spectrophotometric analysis in a finger, deriving 100 transmittance spectra per second, to resolve optical spectra (900 to 1700 nm) of blood volume pulsations throughout the cardiac cycle. Difference spectra are calculated from the pulsatile signals, thereby eliminating the effects of bone, other tissues, and nonpulsatile blood. A partial least squares (PLS) model is used with the measured spectral data to predict BGL levels. Using glucose tolerance tests in 27 healthy volunteers, periodic optical measurements were made simultaneously with collection of blood samples for in vitro glucose analysis. Altogether, 603 paired data sets were obtained in all subjects and two-thirds of the data or of the subjects randomly selected were used for the PLS calibration model and the rest for the prediction. Bland-Altman and error-grid analyses of the predicted and measured BGL levels indicated clinically acceptable accuracy. We conclude that the new method, named pulse glucometry, has adequate performance for safe, noninvasive estimation of BGL.

Nitric oxide contribution to vascular wall oxygen consumption in arterioles

To study the role of nitric oxide (NO) in regulating oxygen consumption by vessel walls, the oxygen consumption rate of arteriolar walls in rat cremaster muscle was measured in vivo during flow-induced vasodilation and after inhibiting NO synthesis. The oxygen consumption rate of arteriolar was calculated based on the intra- and peri-vascular oxygen tension (P0(2)) values measured by phosphorescence quenching laser microscopy. The peri-vascular PO(2) value of the arterioles during vasodilation was significantly higher than under control conditions, although the intravascular PO(2) values under both conditions were approximately the same. On the other hand, inhibition of NO synthesis caused a significant decrease in both the intra- and peri-vascular P0(2) values of the arterioles. The inhibition of NO synthesis increased the oxygen consumption rate of the walls by 42%, whereas enhancement of flow-induced NO release decreased it by 34%. These results suggest that NO plays an important role not only as a regulator of peripheral vascular tone, but also as a modulator of tissue oxygen consumption by reducing oxygen consumption by vessel walls.

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.

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.

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).

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.

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.

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.

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.

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.

Restoration of tensile properties at tendon insertion to bone by a patellar tendon-tibia autograft: an experimental study with canine infraspinatus

A free patellar tendon-tibia autograft was performed to reconstruct a tendon insertion to bone of the canine infraspinatus. In this experimental study restoration of mechanical properties at tendon insertion to bone of the patellar tendon-tibia autograft was examined on 0, 42, and 84 postoperative days. Five dogs were used for each time point. Bone union occurred in all grafts by 6 postoperative weeks. The ultimate strength at the tendon insertion to bone recovered from 255.5 N on 0 day to 264.3 N and 439.3 N on 42 and 84 postoperative days, respectively. Stiffness recovered from 141.8 KN/m on 0 day to 201.8 KN/m and 226.3 KN/mN on 42 and 84 postoperative days, respectively. Our results demonstrate that patellar tendon-tibia autograft maintains excellent mechanical properties at tendon insertion to bone in the early healing period. This result suggests that transfer or free graft of tendons with attaching bone plug has a mechanical advantage for reconstruction of the rotator cuff, which may allow the patient to institute early postoperative mobilization.

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.

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.

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.

Mechanical strength of latissimus dorsi tendon transfer with Teflon felt augmentation

Tensile properties of Teflon felt augmentation after latissimus dorsi tendon transfer to rotator cuff defect were examined in dog cadaver shoulders. Two experimental groups with latissimus dorsi tendon transfer were designed. In group 1 (right shoulders, n = 7) the tendon ends of latissimus dorsi were sutured to the greater tuberosity. In group 2 (left shoulders, n = 7) the repair was augmented with Teflon felt at the suture site. The ultimate tensile force and stiffness of each specimen in group 2 were individually compared with those in group 1. The average increases in ultimate tensile force and stiffness in group 2 were 53.8% and -3.7%, respectively. The individual value of ultimate tensile force in group 2 was significantly greater than that in group 1. These results demonstrate that augmentation at the repair site is mechanically effective latissimus dorsi tendon transfer. The augmentation procedure may provide protection during the healing period because of this and a surrounding fibrous tissue reaction.

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.

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.

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.

Fetal and neonatal cerebral oxygen monitoring with NIRS: theory and practice

Near infra-red spectroscopy (NIRS) is a comparatively new method for monitoring the oxygenation in blood and tissue in the brain of the fetus and the neonate. Absorption of light in the wavelength range 700-1000 nm through such tissue is measured, which is then used to calculate changes in the concentration of cerebral oxygenated and de-oxygenated haemoglobin (HbO2 and Hb) and hence cerebral blood volume (CBV). Studies carried out on several groups of newborn babies have shown clear changes in HbO, Hb and CBV with hypoxia and bradycardia. These changes may well have implications in the occurrence of hypoxic/ischaemic brain injury. Intra partum NIR measurements on the fetal brain have demonstrated clear changes in HbO2, Hb and CBVm, coinciding with the onset of contractions.

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.

An experimental evaluation of isometric placement for extraarticular reconstructions of the anterior cruciate ligament

We measured the changes in distance between the tibial and femoral attachment points of the extraarticular ACL substitute during knee motion. To measure the changes in distance continuously and directly, a computer-assisted experimental system was developed using an electrolyte-in-rubber transducer. We used 6 cadaveric knees to measure changes in distance of 15 combinations during a simple flexion and extension knee motion. The distance became longer with flexion in each pair of attachment locations. Although the smallest change in distance was obtained between the posterolateral site of the femoral distal metaphysis and a point posterior to the Gerdy tubercle (percent average of the maximum strain was about 12%), it was concluded that the extraarticular ACL reconstruction is not recommended from a standpoint of isometry of the substitute.

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.

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.

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.

[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.

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.

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.

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.

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.

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.

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.