平野 陽豊

Anticipation of pain engenders anxiety and fear, potentially shaping pain perception and governing bodily responses such as peripheral vasomotion through the sympathetic nervous system (SNS). Sympathetic innervation of vascular tone during pain perception has been quantified using a peripheral arterial stiffness index; however, its innervation role during pain anticipation remains unclear. This paper reports on a neuroimaging-based study designed to investigate the responsivity and attribution of the index at different levels of anticipatory anxiety and pain perception. The index was measured in a functional magnetic resonance imaging experiment that randomly combined three visual anticipation cues and painful stimuli of two intensities. The peripheral and cerebral responses to pain anticipation and perception were quantified to corroborate bodily responsivity, and their temporal correlation was also assessed to identify the response attribution of the index. Contrasting with the high responsivity across levels of pain sensation, a low responsivity of the index across levels of anticipatory anxiety revealed its specificity across pain experiences. Discrepancies between the effects of perception and anticipation were validated across regions and levels of brain activity, providing a brain basis for peripheral response specificity. The index was also characterized by a 1-s lag in both anticipation and perception of pain, implying top-down innervation of the periphery. Our findings suggest that the SNS responds to pain in an emotion-specific and sensation-unbiased manner, thus enabling an early assessment of individual pain perception using this index. This study integrates peripheral and cerebral hemodynamic responses toward a comprehensive understanding of bodily responses to pain.

BACKGROUND: People who were previously hospitalised with stroke may have difficulty operating a motor vehicle, and their driving aptitude needs to be evaluated to prevent traffic accidents in today's car-based society. Although the association between motor-cognitive functions and driving aptitude has been extensively studied, motor-cognitive functions required for driving have not been elucidated. METHODS: In this paper, we propose a machine-learning algorithm that introduces sparse regularization to automatically select driving aptitude-related indices from 65 input indices obtained from 10 tests of motor-cognitive function conducted on 55 participants with stroke. Indices related to driving aptitude and their required tests can be identified based on the output probability of the presence or absence of driving aptitude to provide evidence for identifying subjects who must undergo the on-road driving test. We also analyzed the importance of the indices of motor-cognitive function tests in evaluating driving aptitude to further clarify the relationship between motor-cognitive function and driving aptitude. RESULTS: The experimental results showed that the proposed method achieved predictive evaluation of the presence or absence of driving aptitude with high accuracy (area under curve 0.946) and identified a group of indices of motor-cognitive function tests that are strongly related to driving aptitude. CONCLUSIONS: The proposed method is able to effectively and accurately unravel driving-related motor-cognitive functions from a panoply of test results, allowing for autonomous evaluation of driving aptitude in post-stroke individuals. This has the potential to reduce the number of screening tests required and the corresponding clinical workload, further improving personal and public safety and the quality of life of individuals with stroke.

This study was conducted with the aim of developing a circuit system that enables the measurement of the moisture content and ion concentration with a simple circuit configuration. Our previous studies have shown that soil can be represented by an equivalent circuit of a parallel circuit of resistors and capacitors. We designed a circuit that can convert the voltage transient characteristics of the soil when a current is applied to it into a square wave and output frequency information and developed an algorithm to analyze the two types of square waves and calculate R and C. Normal operation was confirmed in the range of 10 kΩ–1 MΩ for the designed circuit, and the calculation algorithm matched within a maximum error of 5%, thus confirming the validity of the program. These successfully confirmed the changes in the water content and ionic concentration. The soil moisture content measurement succeeded in measuring a maximum error of about 10%, except at one point, and the soil ion concentration measurement succeeded in measuring a maximum error of 6.6%. A new, simple, noise-resistant moisture content and ion concentration measurement circuit system with square wave output has been realized.

An ISFET-type pH sensor with stripe gate electrodes to inhibit the drift was fabricated for long-term pH measurement. The line and space patterns of stripe gate electrodes were fabricated under the pH sensing membrane in a channel area of the FET. The voltage was applied to the gate electrodes to suppress the diffusions of the anions from the object solution in the sensing membrane. We confirmed the inhibition of the drift using the gate electrodes.

【目的】著者らは血管内皮機能評価法として，虚血反応性充血後の血管拡張能をオシロメトリックの原理を用いて計測するenclosed zone flow-mediated dilation (ezFMD) 検査を提案している．しかし，血管拡張は血管内皮機能による血管壁弛緩だけでなく，血圧変動にも影響される．そこで本研究では，ezFMD検査における血圧変動に依存しない新しい血管内皮機能評価指標を提案する．【方法】広島大学・医の倫理委員会承認のもと，事前にインフォームド・コンセントが得られた健常群25名（27.6±13.6歳），動脈硬化ハイリスク群21名（56.0±15.3歳）を対象としezFMD検査を行った．カフ印加圧とカフ容積脈波から血圧変動を考慮したパラメータである血管粘弾性を推定し，血管粘性を血管剛性で除した補正粘性の駆血前後での変化率を血管内皮機能の評価指標としてROC解析を行った．【結果】各群での提案指標の平均は，健常群116.4±122.9%，動脈硬化ハイリスク群2.1±43.2%であり，2群間に有意差を確認した（p = 1.8 × 10-6）．また，AUC値は提案指標で0.85，従来法では0.62であった．【結論】提案した補正粘性変化率により，血圧変動に依存せず血管内皮機能を評価できることが明らかになった．

【目的】ヒトの疼痛を客観的に定量評価することを目的として，著者らは末梢交感神経活動を反映する血管剛性と電気刺激時の主観的疼痛度の間に有意な関係があることを見出した．本報告では，血管剛性から筋交感神経信号の分散を非侵襲推定し，推定した分散から主観的疼痛度をより高精度で客観的に定量評価する方法を提案する.【方法】広島大学・医の倫理委員会承認のもと事前にインフォームド・コンセントが得られた健常成人男性22名（22.7±1.0歳）を対象に皮膚電気刺激実験を行った．刺激中の心電図，血圧，指尖容積脈波から求めた血管剛性を用いて筋交感神経信号の分散を推定した．その後，ウェーバー・フェヒナー則を用いて筋交感神経信号の分散と主観的疼痛度の関係をモデル化し，モデルによる推定値と実測値との相関解析を行った．比較のため，血管剛性と主観的疼痛度の間においても同様の解析を行なった.【結果】筋交感神経信号の分散から推定した主観的疼痛度と実測した主観的疼痛度の相関は，血管剛性の場合と比較して上昇した(提案法: r ＝ 0.60, p < 0.001, 血管剛性: r ＝ 0.47, p < 0.001).【結論】提案法は主観的疼痛度を従来法より高精度かつ客観的に定量評価可能であった.

This paper proposes a novel technique to estimate continuous pulse pressure waves based on aortic pulse waves (APWs) that are measured in an unconstrained manner at the back of a user via an APW sensor. Frequency filtering and rectification are applied to the APWs as a preprocessing step. These preprocessed waves are then converted into continuous pulse pressure waves using a black box model that includes the physical factors of the patient. The black box model is constructed beforehand using the preprocessed APWs and continuous arterial pressure waves measured from other users. The converted pulse pressure waves were then compared with continuous arterial pressure waves measured using a commercial sphygmomanometer to evaluate the accuracy of the proposed method. As a result, the correlation coefficient between the converted waves from the proposed method and the waves measured using the sphygmomanometer was 0.83 or higher and the mean absolute error was 6.07 +/- 5.89 mmHg It was therefore concluded that the proposed method may enable unconstrained measurement of continuous pulse pressure waves.

This paper proposes a novel non-invasive method for assessing the vascular endothelial function of lower-limb arteries based on the dilation rate of air-cuff plethysmograms measured using the oscillometric approach. The principle of evaluating vascular endothelial function involves flow-mediated dilation. In the study conducted, blood flow in the dorsal pedis artery was first monitored while lower-limb cuff pressure was applied using the proposed system. The results showed blood flow was interrupted when the level of pressure was at least 50 mmHg higher than the subject's lower-limb systolic arterial pressure and that blood flow velocity increased after cuff release. Next, values of the proposed index, %ezFMD L, for assessing the vascular endothelial function of lower-limb arteries were determined from 327 adult subjects: 87 healthy subjects, 150 subjects at high risk of arteriosclerosis and 90 patients with cardiovascular disease (CAD). The mean values and standard deviations calculated using %ezFMD L were 30.5 ± 12.0% for the healthy subjects, 23.6 ± 12.7% for subjects at high risk of arteriosclerosis and 14.5 ± 15.4% for patients with CAD. The %ezFMD L values for the subjects at high risk of arteriosclerosis and the patients with CAD were significantly lower than those for the healthy subjects (p &lt 0.01). The proposed method may have potential for clinical application.

A low-leakage-current-type impedance sensor chip with shield structures has been fabricated. The low limit detection of soil-water-content measurement was improved compared with that of the other semiconductor-type sensors. The shield structures were fabricated under the impedance sensor areas. To measure the weak signal current eliminated by the leakage current, we proposed a new operation circuit to separate the leakage current. Our sensor was able to measure low water content of 10% or less. The sensor could detect the change of water content in the slope of mountain when it rained.

BACKGROUND: Reliable analgesia monitoring is not available for general anaesthesia cases. In 2003, we introduced a method to characterise arterial mechanical properties, which we termed arterial stiffness (K). However, it is unclear whether differences in K actually indicate changes in the intensity of a noxious stimulus. Thus, we examined the relationship between stress intensity and the value of K. METHODS: Thirty patients under general anesthesia were randomly divided into two remifentanil concentration groups (2 and 6 ng/mL). After a steady concentration of remifentanil was achieved for at least 3 minutes, laryngoscopy was performed. After completion of laryngoscopy, once the K value returned to near-baseline, laryngoscopy with endotracheal intubation was performed, and the value of K after the procedure was recorded and analyzed. RESULTS: In total, data were obtained for 28 of 30 patients. The values of K before the laryngoscopy were not significantly different between the groups (2 ng/mL group: 13.1 [8.5-33.1] mmHg/% 6 ng/mL group: 11.6 [4.3-31.4] mmHg/% P=0.53). After laryngoscopy, K was approximately 2 times greater in the 2 ng/mL group than in the 6 ng/mL group (39.0 [13.6-115.9] mmHg/% vs. 19.0 [5.5-85.1] mmHg/%, P=0.02). After intubation also, K was approximately 2 times greater in the 2 ng/mL group (52.0 [27.7-122.0] mmHg/% vs. 24.3 [7.2-94.9] mmHg/%, P=0.04). CONCLUSIONS: The value for arterial stiffness (K) non-proportionally changes in response to stimulus intensity therefore, it has the potential to be used as an indicator of nociceptive stimulation intensity.

In clinical practice, subjective pain evaluations, e.g., the visual analogue scale and the numeric rating scale, are generally employed, but these are limited in terms of their ability to detect inaccurate reports, and are unsuitable for use in anesthetized patients or those with dementia. We focused on the peripheral sympathetic nerve activity that responds to pain, and propose a method for evaluating pain sensation, including intensity, sharpness, and dullness, using the arterial stiffness index. In the experiment, electrocardiogram, blood pressure, and photoplethysmograms were obtained, and an arterial viscoelastic model was applied to estimate arterial stiffness. The relationships among the stiffness index, self-reported pain sensation, and electrocutaneous stimuli were examined and modelled. The relationship between the stiffness index and pain sensation could be modelled using a sigmoid function with high determination coefficients, where R2 ≥ 0.88, p < 0.01 for intensity, R2 ≥ 0.89, p < 0.01 for sharpness, and R2 ≥ 0.84, p < 0.01 for dullness when the stimuli could appropriately evoke dull pain.

【目的】脳卒中患者が気分障害や認知機能低下を呈すると生活の質が著しく低下するが，それらの機序は解明されていない．本研究では脳卒中患者を対象とし，気分障害はDepression, Apathy, Anxietyに注目し，認知・身体機能等の各種検査から得られる指標との関連性について機械学習を用いて解析を行う．【方法】広島大学・医の倫理委員会承認のもと，事前にインフォームド・コンセントが得られた脳卒中患者207名（64.4±10.2歳）を対象とし，機能的自立度評価法，認知機能検査（注意機能，記銘力等），自覚ストレス検査を課した．また，Hospital Anxiety and Depression Scaleとやる気スコアから気分障害の有無を判定した．気分障害の有無を教師信号，機能評価検査の指標得点を入力として，確率ニューラルネットワークの一つであるLog-Linearized Gaussian Mixture Network (LLGMN)を用いてleave-one-subject-out交差検証を行い，気分障害の有無の識別精度を評価した．また，偏KL情報量を用いた入力次元削減により識別精度向上と識別に重要な指標の特定を試みた．【結果】Depressionは82.8%，Apathyは69.8%，Anxietyは86.2%の精度で気分障害の有無が識別できた．【結論】LLGMNを用いた機械学習により，Depression, Apathy, Anxietyという各種の気分障害に関連する重要な指標を特定できる可能性がある．

Blood flow monitoring systems such as photoplethysmogram (PPG) and laser Doppler flowmetry (LDF) are useful for intraoperative determination of a successful endoscopic thoracic sympathectomy (ETS) procedure, as they are able to indicate a sympatholytic response. A recently developed novel arterial mechanical impedance monitor has been shown able to provide a value for peripheral arterial stiffness, shown as K. In this retrospective cohort study, we compared the intensity of K with that of PPG and LDF during ETS procedures. Seventy-nine patients with hyperhidrosis underwent a surgical sympathectomy procedure under general anesthesia, during which they were managed by monitors attached to the tips of their fingers. Circulatory variables before and after the surgical procedure were recorded during ETS, then the ratios of those indices were statistically compared. With a statistical significance level of p &lt; 0.05, K was shown to have a greater alteration as compared to PPG and LDF at the time of skin incision as well as neural clipping in both hands. We concluded that arterial mechanical impedance shown by K is a more sensitive monitor of sympathetic activity derived from vasoconstriction and vasodilation during an ETS procedure as compared to PPG and LDF.

A low-leakage-current type impedance sensor chip with shield structures has been fabricated. The low limit detection of soil-water-content measurement was improved compared with that of the other semiconductor type sensors. The shield structures were fabricated under the impedance sensor areas. To measure weak signal current eliminated the leakage current, we proposed a new operation circuit to separate the leakage current. Our sensor achieved to measure low water content 10 % or less.

The presence of an earlobe crease (ELC) may be a simple sign to predict atherosclerosis. We evaluated the relation between ELC and vascular function. We measured flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID) and observed bilateral earlobes in 400 consecutive subjects. At first, the subjects were divided into 3 groups: non-ELC group, unilateral ELC group, and bilateral ELC group. FMD and NID were significantly lower in the unilateral and bilateral ELC groups than those in the non-ELC group. After adjustment of cardiovascular risk factors, bilateral ELC, but not unilateral ELC, was associated with lower FMD and lower NID. We also investigated whether an increase in the number of ELCs worsens endothelial function, whether the difference in ELC structure (cross stripes and/or ramification) affects endothelial function, and whether endothelial function is impaired in subjects with superficial wrinkles depending on age. The number of ELCs, shape of the ELC, and superficial wrinkles were not associated with endothelial dysfunction. In conclusion, these findings suggest that the presence of bilateral ELCs is associated with vascular dysfunction. (C) 2017 Elsevier Inc. All rights reserved.

Background-A new device for automatic measurement of flow-mediated vasodilation (FMD) using an oscillometric method has been developed to solve technical problems of conventional FMD measurement. This device measures enclosed zone FMD (ezFMD). The purpose of this study was to evaluate the prognostic value of endothelial function assessed by ezFMD for future cardiovascular events. Methods and Results-We measured ezFMD in 272 participants who underwent health-screening examinations. First, we investigated cross-sectional associations between ezFMD and cardiovascular risk factors, and then we assessed the associations between ezFMD and first major cardiovascular events (death from cardiovascular causes, stroke, and coronary revascularization). Univariate regression analysis revealed that ezFMD was significantly correlated with age, triglycerides, glucose, smoking packyears, estimated glomerular filtration rate, high-sensitivity C-reactive protein, and Framingham risk score. During a median followup period of 36.1 months (interquartile range 18.8-40.1 months), 12 participants died (6 from cardiovascular causes), 3 had stroke, 8 had coronary revascularization, and 10 were hospitalized for heart failure. There was no episode of acute coronary syndrome during the study period. Participants were divided into tertiles (low, intermediate, and high) based on ezFMD. Kaplan-Meier curves for first major cardiovascular events among the 3 groups were significantly different (P=0.004). After adjustment for cardiovascular risk factors, the low group was significantly associated with an increased risk of first major cardiovascular events compared with the high group (hazard ratio 6.47; 95% CI 1.09-125.55; P=0.038). Conclusions-These findings suggest that endothelial function assessed by ezFMD may be useful as a surrogate marker of future cardiovascular events.

Little is known about the effect of sweet taste stimulus on gastrointestinal motility and splanchnic blood flow. We examined whether gastric myoelectrical activity and/or celiac artery blood flow (CABF), which perfuses the stomach, are increased following an oral sensation of sweetness. After overnight fasting, 11 subjects rested for 5min and sipped, but not swallowed, one of four solutions for 1min. The fluid was then spat out, and subjects remained at rest for a further 10min. Fluids were approximately 15ml of three glucose solutions (4, 16, or 48%) or distilled water. Subjects completed trials with all four solutions in a randomized order. During each trial, gastric myoelectrical activity and CABF were continuously measured using electrogastrography and pulsed Doppler ultrasonography, respectively. None of the four solutions affected gastric myoelectrical activity. CABF was significantly increased after oral stimuli by all three glucose solutions, but not by water. There were no significant differences in the increments in CABF among the three glucose solutions. These results suggest that a sweet taste stimulus above a certain level of intensity acutely increases CABF during cephalic phase, without augmentation of gastric myoelectrical activity.

It is well known that an earlobe crease (ELC) is related with cardiovascular disease. However evaluation of ELC has been carried out subjectively. We propose a novel system for objective and quantitative evaluation of ELC characteristics. The outline of earlobe was detected using the Canny edge detector. The number of ELCs and the ratio of the ELC length for the lobule from photographs of bilateral earlobes were calculated from the extracted outline of earlobes. Our system's validity for ELCs detection was compared with doctors' diagnosis using sensitivity and specificity analysis. The result showed that the validity of our system was equal to the diagnosis of the medical doctors (kappa coefficient: 0.93). It was thus concluded that the proposed system is useful to predict atherosclerotic disease.

This paper proposed a novel objective pain intensity assessment technique using the change of peripheral arterial stiffness &beta;, which reacts to a peripheral sympathetic nervous activity. The stiffness &beta; is calculated from continuous arterial pressures and photo-plethysmograms beat-by-beat based on the log-linearized peripheral arterial model. In the experiment, the validity of the proposed method was examined by comparing estimated normalized arterial stiffness &beta;_n with simultaneously-measured numeric rating scale (NRS) as a general index of pain intensity when electrocutaneous stimuli were applied to the healthy subjects. The results showed the maximum amplitude of electrocutaneous current I_max has linear correlation with the normalized stiffness &beta;_n (R² =0.77, p < 0.05). In addition, both the maximum amplitude of electrocutaneous current I_max and the normalized stiffness &beta;_n strongly correlated with NRS values by sigmoidal curves (I_max v.s. NRS: R² =0.91, p < 0.01; &beta;_n v.s. NRS: R² =0.92, p < 0.01). It was therefore concluded that the proposed method can assess pain intensity objectively.

This paper proposes a novel diagnosis support method based on peripheral autonomic nervous activity for patients with Parkinson's disease (PD). The method measures rates of change in fingertip plethysmograms and arterial stiffness in transition between a supine position and a standing position of a subject, and calculates fingertip plethysmogram and arterial stiffness changes associated with angular variation from the pre-standing supine position to the standing position during a head-up tilt test. Based on the measured indices, the classification probability of PD presence is finally obtained as a biomarker using a log-linearized Gaussian mixture network. 25 patients with PD symptoms (15 with autonomic defects and 10 without) took part in the experiment. The results showed non-significant differences between the patient groups with autonomic defects and without autonomic defects in comparison of each single index on fingertip plethysmogram and arterial stiffness, but a significant difference (p<0.001) between the two groups was observed in the output index of the proposed system. Moreover, receiver operation characteristics (ROC) analysis showed that the area under the curve (AUC) of the proposed biomarker was 0.83 and the classification rate of PD presence was 100% for the learning data and 80% for the unlearned test data.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved. This study proposes a novel noninvasive arterial stiffness estimation technique based on the oscillometric method and applies it to assess the vascular endothelial function. Change of the arterial stiffness during the enclosed zone flow-mediated dilation test was calculated from the measured blood pressure, the cuff oscillation, and the applied pressure to the cuff. As results, the arterial stiffness change for the four healthy subjects was -42±17% and that for the four patients with high-risk of arteriosclerosis was -2.9±11%. The mean changes had significantly different between the two groups (p<0.01). The result thus indicated proposed method could assess the vascular endothelial function.

This paper proposes a novel palpable and non-invasive continuous sphygmomanometer, with which continuous arterial pressure can be measured based on electromagnetic induction. The proposed sensor can be attached to the measurer's fingertip, and single-degree-of-freedom springs, which are interposed between the side of the measurer's finger and the skin surface side, transmit the arterial pressure to the measurer. At the same time, displacements of the springs are measured by electromagnetic induction, and converted into a measurement of arterial pressure. This mechanism allows measurement of the continuous arterial pressure based on a tonometry approach. In the experiment, the conversion equations from the output voltage to arterial pressure values were verified by comparison with the arterial pressure measured using a commercial continuous sphygmomanometer. The experimental results showed that the determination coefficient of the regression line between arterial pressures measured using the sensors was 0.89 (p < 0.01). Therefore we can conclude that the proposed sensor enables the non-invasive measurement of continuous arterial pressure.

The flow-mediated dilation (FMD) test is a method of evaluating the vascular endothelial function and has been popular as it is noninvasive and readily performed by a skillful ultrasound technician. The FMD test, however, evaluates only the maximal increase in vascular diameter mediated by the increases in blood flow after the release of the occlusive cuff and does not evaluate the arterial viscoelastic properties. Therefore, this paper proposes a new index, called log-linearlized viscoelasticity, to evaluate the arterial viscoelastic properties using the arterial diameter and blood pressure measured in a beat-to-beat manner during the FMD test. To six healthy people, we performed the FMD test to measure the arterial diameter and blood pressure with ultrasound diagnostic imaging equipment and noninvasive continuous arterial blood pressure monitor. As a result, the maximal vasodilatation ratio of FMD (%FMD) was obtained after cuff occlusion. In comparison with the arterial viscoelastic characteristics before FMD test, the stiffness of the arterial wall &beta; and the viscosity of the artery &eta; temporarily decreased and increased, respectively. The change of log-linearlized viscoelasticity after cuff occlusion may be caused by vascular endothelial function. Vascular endothelial function might thus be estimated using the arterial viscoelasticity &beta; and &eta;.

The paper discusses the arterial stiffness during the flow-mediated dilation (FMD) test. The FMD test is a method of evaluating the vascular endothelial function and has been popular as it is non-invasive and readily performed by a skillful ultrasound technician. The FMD test, however, evaluates only the maximal increase in vascular diameter mediated by the increases in blood flow after the release of the occlusive cuff and does not evaluate the arterial viscoelastic properties. This paper thus estimates the log-linearlized stiffness, to evaluate the arterial stiffness properties using the arterial diameter and blood pressure measured in a beat-to-beat manner during the FMD test. To six healthy volunteers, we performed the FMD test to measure the arterial diameter and blood pressure with ultrasound diagnostic imaging equipment and non-invasive continuous arterial blood pressure monitor, respectively. As a result, the maximal vasodilatation ratio of FMD (FMD) was obtained after cuff occlusion. In comparison with the arterial stiffness before the FMD test, the stiffness of the arterial wall is temporarily decrease and increase. It was concluded the the arterial stiffness can be estimated on a beat-to-beat basis during the FMD test. © 2013 IEEE.

This paper proposes a method for qualitatively estimating the mechanical properties of arterial walls on a beat-to-beat basis through noninvasive measurement of continuous arterial pressure and arterial diameter using an ultrasonic device. First, in order to describe the nonlinear relationships linking arterial pressure waveforms and arterial diameter waveforms as well as the viscoelastic characteristics of arteries, we developed a second-order nonlinear model (called the log-linearized arterial viscoelastic model) to allow estimation of arterial wall viscoelasticity. Next, to verify the validity of the proposed method, the viscoelastic indices of the carotid artery were estimated. The results showed that the proposed model can be used to accurately approximate the mechanical properties of arterial walls. It was therefore deemed suitable for qualitative evaluation of arterial viscoelastic properties based on noninvasive measurement of arterial pressure and arterial diameter.

This paper proposes a novel technique to support the monitoring of peripheral vascular conditions using biological signals such as electrocardiograms, arterial pressure values and pulse oximetry plethysmographic waveforms. In this approach, a second-order log-linearized model (referred to here as a log-linearized peripheral arterial viscoelastic model) is used to describe the non-linear viscoelastic relationship between blood pressure waveforms and photo-plethysmographic waveforms. The proposed index enables estimation of peripheral arterial wall stiffness changes induced by sympathetic nerve activity. The validity of the method is discussed here based on the results of peripheral vascular condition monitoring conducted during endoscopic thoracic sympathectomy (ETS). The results of ETS monitoring showed significant changes in stiffness variations between the periods before and during the procedures observed (p < 0.01) as well as during and after them (p < 0.01), so that it was confirmed that sympathetic nerve activity is drastically decreased in the area around the monitoring site after the thoracic sympathetic nerve trunk on the monitoring side is successfully blocked. In addition, no change was observed in the values of the proposed index during the ETS procedure on the side opposite that of the monitoring site. The experimental results obtained clearly show the proposed method can be used to assess changes in sympathetic nerve activity during ETS.

This paper proposes a novel non-invasive and palpable measurement sensor for carotid pulse pressure. The unit consists of a pair of coil printed circuit boards, a pair of springs and a sensing plastic chip, with each spring attached between the circuit board and the chip. The distance between the boards is monitored from the displacement of the springs, and the information is converted into a voltage signal based on electromagnetic induction. First, the optimal forces externally applied to the proposed sensor were examined to allow accurate measurement of carotid pulse wave amplitude variations. It was found that the force applied when the measured maximum amplitudes of the sensor were obtained yielded the best performance. Next, carotid pulse waves were measured using the sensor with these optimal forces, and the results were compared with carotid pulse pressure values measured using a commercialized pulse wave transducer. The resulting coefficient of correlation between the two carotid waves was 0.9 or more. It was therefore concluded that the proposed sensor enables non-invasive measurement of carotid pulse waves.