© 2016 IEEE. The authors examined the hemodynamic characteristics of expanded polytetrafluoroethylene (ePTFE) pulmonary valved conduits quantitatively by our originally developed pediatric pulmonary mechanical circulatory system, in order to suggest the optimal shape design. The system consisted of pneumatically driven right atrium and ventricle model, a pulmonary valve chamber, and elastic pulmonary compliance model with peripheral vascular resistance units, a venous reservoir. We employed two different types of ePTFE valve and evaluated the relationship between the leaflets motion and hemodynamic characteristics by using a high-speed video camera. As a result, we successfully reproduced hemodynamic simulations in our pediatric pulmonary mock system. We confirmed that the presence of bulging sinuses in the pulmonary valved conduit reduced the transvalvular energy loss and increased the valve opening area during systolic period. Our engineering-based in vitro analysis could be useful for proposing a shape design optimization of sophisticated pediatric ePTFE pulmonary valve.

© 2015, The Japanese Society for Artificial Organs. Implantation of a total artificial heart (TAH) is one of the therapeutic options for the treatment of patients with end-stage biventricular heart failure. There is no report on the hemodynamics of the functional centrifugal-flow TAH with functional atrial contraction (fCFTAH). We evaluated the effects of pulsatile flow by atrial contraction in acute animal models. The goats received fCFTAH that we created from two centrifugal-flow ventricular assist devices. Some hemodynamic parameters maintained acceptable levels: heart rate 115.5 ± 26.3 bpm, aortic pressure 83.5 ± 10.1 mmHg, left atrial pressure 18.0 ± 5.9 mmHg, pulmonary pressure 28.5 ± 9.7 mmHg, right atrial pressure 13.6 ± 5.2 mmHg, pump flow 4.0 ± 1.1 L/min (left) 3.9 ± 1.1 L/min (right), and cardiac index 2.13 ± 0.14 L/min/m2. fCFTAH with atrial contraction was able to maintain the TAH circulation by forming a pulsatile flow in acute animal experiments. Taking the left and right flow rate balance using the low internal pressure loss of the VAD pumps may be easier than by other pumps having considerable internal pressure loss. We showed that the remnant atrial contraction effected the flow rate change of the centrifugal pump, and the atrial contraction waves reflected the heart rate. These results indicate that remnant atria had the possibility to preserve autonomic function in fCFTAH. We may control fCFTAH by reflecting the autonomic function, which is estimated with the flow rate change of the centrifugal pump.

© 2016 The Japan Society of Mechanical Engineers. Improving the inflow characteristics of the right ventricular function and pulmonary circulatory hemodynamics was essential for more precise evaluation of newly designed heart valves. To examine a pulmonary hemodynamics, the authors have been developing a pulmonary mechanical mock circulatory system. In this study, the pneumatically driven right atrium model was newly developed for clarifying the effect of atrial contraction on the dynamic behavior of pulmonary prosthetic valves. We focused on the hemodynamic behavior of the outflow mechanical heart valve of the right ventricle that could be affected by the right atrial dynamic motion. A medical-grade bileaflet valve was employed and installed into the outflow portion of the right ventricle model and examined its changes in hemodynamic behavior caused by the active right atrial contraction. With the active atrial contraction, hemodynamic waveforms of either the right ventricle or atrium were obtained using the modified pulmonary mock circulatory system. The characteristics with atrial contraction were well simulated as the natural hemodynamics. The right ventricular output increased by around 5% and the peak regurgitant flow at the moment of valve closing significantly decreased by the presence of the atrial contraction. Our mechanical circulatory system could simulate the end-diastolic right ventricular inflow characteristics. We found that the atrial contraction under the low pressure condition such as pulmonary circulation promoted earlier valve closing and prolonged closing duration of prosthetic valve. The simulation of right atrial contraction was important in the quantitative examination of right heart prosthetic valves for congenital heart malformation.

© 2015 IEEE. Pulmonary conduit valves are used as one of the surgical treatment methods of congenital heart diseases. We have been designing a sophisticated pulmonary conduit valve for the right ventricular outflow tract reconstruction in pediatric patients. In this study, two types of polyester grafts with or without bulging structures for the conduit valves were used and evaluated from the hemodynamic point of view focusing on the application of these conduit valves in the grown-up congenital heart failure patients. We examined valvular function in the originally developed pulmonary mock circulatory system, which consisted of a pneumatic driven right ventricular model, a pulmonary valve chamber, and an elastic pulmonary compliance model with peripheral vascular resistance units. Prior to the measurement, a bileaflet valve was sutured in each conduit. Each conduit valve was installed in the mock right ventricular outflow portion, and its leaflet motion was obtained by using a high-speed camera synchronously with pressure and flow waveforms. As a result, we could obtain hemodynamic changes in two different types of conduits for pulmonary valves, and it was indicated that the presence of the Valsalva shape might be effective for promoting valvular response in the low cardiac output condition.

© 2015, The Japanese Society for Artificial Organs. The Fontan procedure is one of the common surgical treatments for circulatory reconstruction in pediatric patients with congenital heart disease. In Fontan circulation, low pulsatility may induce localized lung ischemia and may impair the development of pulmonary peripheral endothelial cells. To promote pulmonary circulation in Fontan circulation, we have been developing a pediatric pulmonary circulatory pulsation device using shape memory alloy fibers attached from the outside of total cavopulmonary connection. In this study, we developed a new thermal control system for the device and examined its functions. We mounted on the device 16 fibers connected in parallel around an ePTFE graft circumferentially. To provide optimized contraction, we designed the new thermal control system. The system consisted of a thermistor, a pressure sensor, and a regulator that was controlled by the adaptive thermodynamic transfer functions. We monitored the parameters and calculated heat transfer function as well as pressure distribution on the graft surface. Then we examined and compared the dynamic contractile pressure and changes in surface temperature. As a result, by the application of the control based on the new feedback system analysis, the circumferential contractile pressure increased by 35 %. The adaptive thermodynamic regulation was useful for the selection of alternative thresholds of the surface temperature of the graft. The system could achieve effective contraction for the pulsatile flow generation by the device.

Right ventricular outflow tract (RVOT) reconstruction surgery is one of the surgical strategies for congenital heart failure, and is commonly used for the treatment of severe heart failure with pulmonary valvular problems. An expanded polytetrafluoroethylene (ePTFE) pulmonary valve was invented for RVOT reconstruction, and the authors have tested its hemodynamic and hydrodynamic characteristics for design improvement. The special features of the ePTFE valve are as follows: (a) anatomically identical trileaflet structure, and (b) bulging sinuses in the vicinity of leaflets. In this study, we used three types of pulmonary valves; an ePTFE valve with bulging sinuses, an ePTFE valve in straight conduit, and a natural pulmonary arterial valve extracted from a goat after the animal experiment. Then we measured the hemodynamic characteristics of the various types of ePTFE valves using a mechanical pulmonary circulatory system. Next, using the pressure and flow data derived from the mechanical circulatory system, we calculated the mechanical design parameters of the ePTFE valves based on a numerical modeling method by inverse analyses. The mathematical parameters we used in the model were inertia, damping, and stiffness coefficients, and we compared these values among three types of pulmonary valves. We succeeded to estimate the mechanical parameters for each valve from the hemodynamic data. The results suggest that the ePTFE valve with bulging sinuses may exhibit similar parametric characteristics to those calculated from the natural pulmonary heart valves.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved. We have been developing several variations of circulatory assist systems based on nano or micro engineering technologies. One of the special features of the design of these new styles of circulatory assist devices will be a passive controllability according to the native physiological signal transmission and hemodynamic responses. In this study, we presented the design features and the research diversity for the development of passive-active circulatory support systems, such as artificial myocardial assist devices, circulatory valves, epi-cardial or vascular support systems for mechanical assistance in chronic or congenital heart failure patients. We employed a covalent type shape memory alloy fiber as the actuator for the implantable artificial internal organs for sophisticated ventricular or hemodynamic support devices.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved. In order to promote peristaltic function in the patients with the end stage of esophageal cancer, we have been developing an implantable artificial esophagus. Surgical treatments, such as gastroesophagostomy, are applied for alternative reconstruction in the patients, however, the peristaltic motion will be eliminated. In this study, we focused on the distributed function in the native esophagus and examined stress-strain characteristics from proximal to distal portion using freshly extracted goat’s esophagus. Prior to the measurement, we developed a new tension test apparatus. As a result, we could evaluate the circumferential esophageal characteristic variations. Then it was suggested that the circumferential stress analysis might be useful for more sophisticated design of artificial esophageal specifications, which would be consistent with the physiological demand as well as the passive structural effects.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved. Stress is an important factor when we consider responses in the cardiovascular and the autonomic nervous systems. After ethical committee allowance, responses in the cardiovascular system and autonomic nerve were evaluated with the individual characteristics. We investigated relationship between responses to the stress and individual characteristics. Healthy adult participants were assessed with type A scale, Beck depression scale, Hostility scale and Japanese Coronary-prone Behavior Scale (JCBS). Participants were showed hateful images and performed a mathematical task (Sudoku). Heart rate (HR), systolic blood pressure (SBP), LF/HF and pulse wave transmission time (PTT) were measured. The maximum value of the cross-correlation coefficients between BP and HR (ρ<inf>max</inf> BH), BP and PTT (ρ<inf>max</inf> BT) were analyzed. In both tasks, higher type A scored groups had larger LF/HF, suggesting that the individual characteristics were correlated with the autonomic nervous system. Significant correlation between the Beck depression score and the decrease in PTT and the increase in BP during hateful images were observed. High type A scored or high depression level had the relationship with the stress.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved. In order to promote the pulmonary circulation after Fontan operation, we developed a pediatric pulmonary circulatory assist device using shape memory alloy fibers. In this study, we developed the sensor-less control system for the pulmonary circulatory assist device and examined its fundamental functions. The SMA fiber showed a linear relationship between the internal resistance and longitudinal contraction. We measured the change in current of the fiber during the operation. Electric current increased from 1.4 to 1.8 A during operation, and the maximum current supply was measured at the end of the contraction. Therefore, we could be estimated the device contraction by the measurement of current which was calculated by voltage sampling of fiber units. Prevention of the overheating of the fiber unit was one of the problem throughout the operation of the device, and we could achieve the elimination of excess current supply by detecting the fiber voltage as well as the estimation of electric power supply without ineffective contraction. Consequently, the method in this study might be applied as a highly reliable totally implantable system.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved. The authors have been developing a pulmonary mechanical circulatory system in order to establish design parameters of artificial cardiovascular assist devices. In the quantitative examination of heart valves in pulmonary mock circulation, interactive changes in pressure and flow are regulated by pulmonary impedance characteristics. We focused on the native characteristics changes in impedance in the pulmonary circulation. To obtain the effect of respiratory control on pulmonary resistance, we measured pulmonary arterial pressure and flow in adult goat under the different respiratory settings with open- and closed-chest condition. We calculated pulmonary input impedance in two respiratory conditions under the anesthetized open-chest positive pressure ventilation (PPV) and the awake spontaneous respiration (SR). Longitudinal impedance in SR showed lower than in PPV. Characteristic impedance in SR was bigger than in PPV. Therefore, we concluded that the pulmonary impedance should be considered for more sophisticated simulation of pulmonary circulatory support devices.

© Springer International Publishing Switzerland 2014.In order to promote activity of daily life of patients with severe esophageal diseases, supporting peristalsis motion at the esophagus might be efficient. So we have been developing an artificial esophagus (AE) which has peristalsis motion function, and we have achieved the AE by using Ni-Ti shape memory alloy fibers. We extracted the esophagus from the epiglottis to the cardia potion from goats, which weighed 48.6±16.3 kg (n=4), after the animal experiment procedures. Prior to the measurement of characteristics of natural esophagus, we defined 5 segments in each extracted esophagus. Then we set the specimen in the static characteristic test apparatus in which we could measure segmental pressure-volume relations. Pressure and volume were measured simultaneously. All these measurement were performed within 3 hours from the extraction. Average length of each esophagus was 63±7cm. Because of the proximal segment of the specimen exhibited that the steeper increase of pressure than the distal portion near the cardia, we characterized that the distal esophagus is firmer than proximal. The proximal segment exhibited 55% bigger increase in pressure than the distal portion near the gastric cardiac part. Therefore it was suggested that compliance at the proximal portion could be lower at the small amount of internal volume. On the other hands, the extensibility of distal esophagus might be bigger than that at proximal segment. Consequently it was indicated that a new mechanical structure could be applied for the development of AE which could reproduce peristaltic motions.

© Springer International Publishing Switzerland 2014. Aim: We have been developing a new aortic blood flow support device using shape memory alloy (SMA) fibers as an actuator. The special features of the device were as follows: a) totally implantable design, b) small and foldable structure with actuators. The system could represent similar function of the aortomyoplasty and the extra aortic balloon pump at the ascending or descending installation. The purpose of this study was to improve the device as a non-blood contacting pulsation system, aiming at the application for the physiologically effective assistance in the artery. Material & Methods: We have designed the prototype by using covalent-type Ni-Ti SMA fibers which is capable of contracting around the aorta circumferentially. In this study, we developed a new structural design with oblique fiber orientations. The device consisted of rubber silicone wall plates, serially connected for radial contraction by the SMA fibers. We reduced the diameter of the contraction by the device. Then we tested the new structural design in the mock system, and examined its functional changes to optimize the mechanical structural design with SMA fibers. We demonstrated the radial deformation effect by using 150 micron Ni-Ti SMA fibers in a multiple circumferential oblique patterns. The orientation and length of the fibers were evaluated by the changes in oblique angles against the longitudinal axis. The fibers were secured circumferentially by using a pair of plastic grooved chambers, where the changes and contractile function was examined for each fiber Result: We could sandwich the aortic tubing of which the diameter was smaller than 30mm, under the constant pressure condition of the aortic tubing at 100mmHg Conclusion: we successfully achieved the improvement of the contraction effects of the SMA fibered device for aortic compression for smaller diameter vessels by the circumferential alignment by oblique angle of fibers.

© Springer International Publishing Switzerland 2014. Hyperactivity of the central nervous system may increase feedback gains in the hemodynamic system. We have been developing a totally implantable renal nerve cooling system which is capable of changing the hyperactive renal nerve function; in particular, those that reversibly eliminate excess signal-gains by using Peltier effects. In this study, we examined the effect of cooling on neurotransmission in vivo and in vitro. Then we evaluated functional characteristics of signal transmission by the change in thermal implication on the nerve to perform thermal sedation of nervous activity. After the animal experimental procedures, we examined the electrical signal transmission in the nerves extracted from the goats. Using the neurogram amplifier and the functional signal generator, we tested the signal transmission characteristics through the nerves and evaluated their filtering functions by regional nerve cooling. In order to examine of natural renal neurotransmission, the renal nerves were dissected from the left kidney in goats under the normal anesthesia using 2.5% of isoflurane. Aortic pressure and the neurogram were measured, and we applied the low-temperature exposure of the nerve. The electric signals exhibited filtered-transmission through the nerve by the cooling in vitro. In the goat’s experiment, the amplitude of the signal which was obtained at the renal nerve decreased when we decreased the nerve surface temperature by -15 degrees. Then we could evaluate these transmission functions of the renal nerve with the interactive changes of the temperature which was to be controlled by the cooling device. We examined characteristics of the signal transmission in the renal nerve in goats by cooling. And we could evaluate these changes in the functional transmission model with the thermal interactions.

© Springer International Publishing Switzerland 2014. Prosthetic materials are used for right ventricular outflow tract (RVOT) reconstruction in cases of congenital heart defects with right ventricular outflow hypoplasia or atresia and for pulmonary valve replacement in the Ross procedure. This procedure is to replace the stenotic pulmonary heart valve such as hypoplastic RVOT by the artificial valved conduit in infants. The authors have been developing a mechanical mock circulatory system for the evaluation of RVOT reconstruction. Improving the inflow characteristics of the right ventricular function and pulmonary circulatory hemodynamics was essentially necessary for more precise evaluation of newly designed heart valves. We developed an original pediatric pulmonary mechanical circulatory system, which was capable of simulating normal pulmonary hemodynamics in children. The system consists of a pneumatic-driven silicone right ventricle, a pneumatic-driven right atrium with a bileaflet polymer valve, a pulmonary valve chamber with a visualization port, a pulmonary arterial compliance tubing, a pulmonary peripheral resistance unit, and a venous reservoir. The mechanical interaction between the right atrium and ventricle was pneumatically controlled by the originally developed microcomputer. Transvalvular pressure waveforms were measured by the pressure transducers and the pulmonary flow was obtained at the outflow portion of right ventricle by the electromagnetic blood flow probe. As a result, hemodynamic waveforms of either the right ventricle or atrium were obtained at the revised pulmonary mock circulatory system. The characteristics with atrial kick were well simulated as the natural hemodynamics. Moreover we could examine the effects of the bulging sinus structure on the valve leaflet motion in the vicinity of the leaflet as well as the atrial contraction. In this study, we simulated natural hemodynamics in our pulmonary circulatory system. We concluded that the simulation of right atrial contraction was inevitable in the quantitative examination of right heart prosthetic valves for congenital heart failure.

Fontan procedure is one of the common surgical treatment of congenital heart diseases. Patients with Fontan circulation have single ventricle in the systemic circulation with the total cavopulmonary connection. Pulmonary blood flow in the Fontan circulation is lower than in healthy subjects, and the central venous pressure may elevate. In this study, we developed a mechanical circulatory assist device for the extracardiac conduit for Fontan circulation and examined its driving method in the mock pediatric pulmonary circulatory system. We used shape memory alloy (SMA) fiber as an actuator of the device. The SMA actuator wrapped the extracardiac conduit between inferior vena cava and pulmonary artery. We designed two different types of the circulatory assist devices. We drove these devices in two different modes by the synchronized and sequential motions. The flow volume was 10mL/min against a load of 10mmHg, and the maximum contractile force indicated 60mmHg in the mock test. These results suggested the effective mechanical assistance for Fontan pulmonary circulation. © 2013 Springer-Verlag.

Diastolic counter-pulsation has been used to provide circulatory augmentation for short term cardiac support. The success of intra-aortic balloon pump (IABP) therapy has generated interest in long term counter-pulsation strategies to treat heart failure patients. The authors have been developing a totally implantable extra aortic pulsation device for the circulatory support of heart failure patients, using 150μm Ni-Ti anisotropic shape memory alloy (SMA) fibers. These fibers contract by Joule heating with an electric current supply. The special features of our design are as follow: non blood contacting, extra aortic pulsation function synchronizing with the native heart, a wrapping mechanical structure for the aorta in order to achieve its assistance as the aortomyoplsty and the extra aortic balloon pump. The device consisted of rubber silicone wall plates, serially connected for radial contraction. We examined the contractile function of the device, as well as it controlling methods; the phase delay parameter and the pulse width modulation, in a systemic mock circulatory system, with a pneumatically driven silicone left ventricle model, arterial rubber tubing, a peripheral resistance unit, and a venous reservoir. The device was secured around the aortic tubing with a counter-pulsation mode of 1-4 against the heartbeat. Pressure and flow waveforms were measured at the aortic outflow, as well as its driving condition of the contraction phase width and the phase delay. The device achieved its variable phase control for co-pulsation or counter-pulsation modes by changing the phase delay of the SMA fibers. Peak diastolic pressure significantly augmented, mean flow increased (p<0.05) according to the pulse width modulation. Therefore the newly developed extra aortic counter-pulsation device using SMA fibers, through it controlling methods indicated its promising alternative extra aortic approach for non-blood contacting cardiovascular circulatory support. © 2013 IEEE.

Fontan procedure is one of the common surgical treatments of congenital heart diseases. Patients with Fontan circulation have single ventricle in the systemic circulation with the total cavopulmonary connection. We have been developing a pulmonary circulatory assist device using shape memory alloy fibers for Fontan circulation with total cavopulmonary connection. It consisted of the shape memory alloy fibers, the diameter of which are 100 μm. The fibers could wrap the ePTFE conduit for Fontan TCPC connection from the outside. We designed the sequential motion control system for sophisticated pulmonary hemodynamics by the pulsatile flow generation. In order to achieve pulsatile flow assistance in pulmonary arterial system, we fabricated a mechanical structure by sequential contraction of shape memory alloy fibers. Then, we developed a sequential contraction controller for the assist system, which could reproduce the wall contractile velocity at 6.0 to 20.0 cm/sec. We examined hemodynamic characteristic of its function using a mock circulatory system, which consisted of two overflow tanks representing venous and pulmonary arterial pressures in Fontan circulation. As a result, the pulmonary circulation assist device with sequential contraction could achieve effective promotion of the pulsatility in pulmonary arterial flow. © 2013 IEEE.

Hemodynamic effects of atrial contraction with centrifugal pump type total artificial heart is unknown. In this study, we simulated an atrial contraction in a mock model. By the driving condition with higher pressure in the mock atrial model, the load during atrial contraction increased. Based on these findings, we examined atrial contraction in the animal using adult goats. Prior to the measurement, we installed a centrifugal-type ventricular assist device (VADs), and then clamped both ventricles. We measured the hemodynamic data without ventricular contractile functions in order to obtain the effect of atrial contraction on hemodynamics under the condition of the total artificial heart (TAH) circulatory support model. We could estimate the heart rate by revolution number and voltage of pumps. There might be a possibility that we could regulate autonomic nervous response with the control of cardiac output. © 2013 IEEE.

The purpose of this study was to examine the hemodynamic characteristics of expanded polytetrafluoroethylene (ePTFE) pulmonary valves with bulging sinuses quantitatively in a pediatric pulmonary mechanical circulatory system designed by us, in order to propose the optimal design for clinical applications. In this study, we developed a pediatric pulmonary mock circulation system, which consisted of a pneumatic right ventricular model, a pulmonary heart valve chamber, and a pulmonary elastic compliance tubing with resistive units. The hemodynamic characteristics of four different types of ePTFE valves and a monoleaflet mechanical heart valve were examined. Relationships between the leaflet movements and fluid characteristics were evaluated based on engineering analyses using echocardiography and a high-speed video camera under the pediatric circulatory conditions of the mock system. We successfully performed hemodynamic simulations in our pediatric pulmonary circulatory system that could be useful for quantitatively evaluating the pediatric heart valves. In the simulation study, the ePTFE valve with bulging sinuses exhibited a large eddy in the vicinity of the leaflets, whereas the straight tubing exhibited turbulent flow. The Reynolds number obtained in the valve with bulging sinuses was calculated to be 1667, which was smaller than that in the straight tubing (R e = 2454). The hemodynamic characteristics of ePTFE pediatric pulmonary heart valves were examined in our mock circulatory system. The presence of the bulging sinuses in the pulmonary heart valve decreased the hydrodynamic energy loss and increased the systolic opening area. Based on an in vitro experiment, we were able to propose an optimal selection of pulmonary valve design parameters that could yield a more sophisticated pediatric ePTFE valve shape. © 2011 The Japanese Society for Artificial Organs.

人工心肺装置操作中に東日本大震災を経験した。地震体験車「ぐらら」を使用し、2種類のハードシェルタイプ静脈リザーバー(リザーバー)を用いて気泡発生の検証を行った。リザーバーには消泡部が最少貯血量より上部にあるタイプ(Q)と下部まで及ぶタイプ(R)のリザーバーにて検証した。気泡検出には、HATTELAND社製CMD20 Microbubble Detectorを用いリザーバー出口に装着し測定した。人工心肺装置(ソーリン社製S-III)を「ぐらら」に載せ、循環流量4L/minの条件にて測定、「ぐらら」の震度は震度5強、震度6強、震度7にて起震し、リザーバー液面レベルを1,500mL、1,000mL、500mLにて気泡混入の測定を行った。Qリザーバーでは、震度5強、液面レベル500mLにて10μmの気泡を検知し、震度6強、震度7、各液面設定にて20μmの気泡を検知した。Rリザーバーでは、震度7にて液面レベル500mLのみ10μmの気泡を検知し、1,500mL、1,000mLでは気泡は検知されなかった。また、Rリザーバーは、貯血量変動や液面からの気泡の引き込みは少なかった。(著者抄録)

冠動脈病変の治療法として冠動脈バイパス術（CABG）と経皮的冠動脈形成術（PCI）があり，複雑な狭窄性病変に関してはCABGが長期予後で優れている．要因として，CABGは冠動脈の分枝血流・微小循環障害を起こさずPCIでは治療困難な病変に治療が行える点が挙げられているが，それらを定量的に示す報告は少ない．当施設では，両治療法が左冠動脈に及ぼすコンプライアンス変化と血行力学的差異の実験的検証のために対角枝，細動脈，微小血管を有し，冠循環の微小循環動態を再現可能な拍動循環回路の開発を進めている．本研究では弾性左冠動脈前下行枝モデルに対して，冠末梢血管の抵抗変動を制御できる機構の開発を試みた．

ローラーポンプ，シリコーン製左冠動脈前下行枝および微小血管モデル，コンプライアンス要素，逆止弁から成る，左冠動脈の血行動態を創出する一巡閉鎖回路を構築した．左冠動脈モデル微小循環部の外部からの圧迫には直動機構を採用し，ローラーポンプの駆動に対して同期あるいは位相制御することで心収縮時に起こる冠末梢血管の抵抗上昇を再現した．

結果，冠動脈特有の二峰性で拡張期優位の流量波形，圧力130/80(96) mmHg，平均流量370 ml/minとなり，冠循環の局所血圧血流環境を創出することに成功した．今後，冠末梢血管抵抗制御機構の改良も含め循環シミュレータの高度化を進め，CABGとPCIにおける治療効果の血行力学的差異の定量評価を実施する．

大動脈二尖弁疾患とは通常3枚ある弁尖が分離発育せず2枚となる先天性疾患である．弁尖が癒合する位置や交連角度の違いにより弁開口形態が多岐にわたり，上行大動脈拡大に影響するとされるが，弁形態ごとの上行大動脈の血流パターンは明らかでない．本研究では，二尖弁疾患における弁形態と上行大動脈の血行動態との関連を定量化するべく，生体大動脈の流量・圧力環境を創出可能かつ，4D-MRIを用いた流れの可視化と血行力学的パラメータの計測が可能な拍動循環シミュレータを開発した．

4D-MRIでの撮像を可能とするため拍動回路の構成要素には非磁性体材料を採用し，流体循環部がMRIのガントリー内に設置可能なサイズに設計した．左室モデル，大動脈弁モデル，弓部大動脈モデル，大動脈コンプライアンスタンク，リザーバタンクからなる一巡回路として構成し，左室モデルの駆動空気圧と末梢抵抗により体循環の血圧・血流を調節可能とした．トリムしたウシ心膜をウシの下行大動脈に縫合することで弁尖枚数や交連角度を任意に設定可能な大動脈弁モデルを作製し，弓部大動脈モデルはヒトの解剖学的形状を模擬し，撮像時のアーチファクト低減のためシリコーンのみで作製した．

三尖の大動脈弁モデルにおいて4D-MRIで撮像した結果，ヒト上行大動脈の流れと同様に左室最大収縮時に直進，収縮末期には時計回りに回旋する流れを取得でき，MRI環境に対応した拍動循環シミュレータを新たに開発できた．

<p>解離性大動脈瘤は血管内膜に生じる亀裂の起点（Entry）から内膜側（真腔）と中外膜（偽腔）間で解離が進展して瘤が拡大するもので，遠位側で偽腔から真腔へ再亀裂（Re-entry）が生じる．ステントグラフト（SG）を用いて真腔側からEntryを閉鎖して瘤内の血流停滞による血栓化を期待する．大動脈の主要分枝血管のSGによる閉鎖は合併症を招くため，Re-entryへのSG留置の必要性の判断が重要となる．本研究では SGをEntry部に留置前後において，EntryとRe-entryの亀裂間の距離が偽腔内血流へ及ぼす影響を明らかにすることを目的とした．真腔・偽腔とEntry・Re-entryを有し解離性大動脈瘤の形態を模擬するシリコーン製弾性血管モデルを開発した．拍動循環回路での生理的圧力・流量条件下で，Entry，Re-entry間距離が異なる3種のモデルのEntry部へSG留置前後の偽腔内部流れを粒子画像流速計測法で可視化した．SG留置後のRe-entryでは偽腔内をEntry側へ吹き上がる流れが残存した．亀裂間距離が長い程，瘤最大拡大部を含む偽腔内の低流速領域が大きくなり，広領域で血栓化が期待できることが示唆された．今後モデル開発を行い，解離性大動脈瘤のSGによる治療戦略につながる研究を行う．</p>

<p>経カテーテル大動脈弁留置術では，血栓関連合併症や留置した弁に血栓ができ弁の正常な運動を抑制する課題があるが，それらの発生要因は明らかになっていない．本研究では経カテーテル大動脈弁留置後のバルサルバ洞内の血流を可視化し，留置した弁の周方向相対角が血流に与える影響を明らかにすることを目的とした．開発した左・右冠動脈血流を創出可能な拍動循環回路を用い，粒子イメージ流速計測法によりバルサルバ洞内の血流を可視化した．大動脈弁に対する経カテーテル弁の周方向相対角を0 deg，60 degの2条件で留置し，バルサルバ洞内の血流に及ぼす影響を検討した．その結果，経カテーテル弁の周方向相対角が60 degの場合，弁開放時にバルサルバ洞内に渦流がほぼ生じず，弁閉鎖時にバルサルバ洞内の弁輪付根部まで流れが流入しないことが明らかとなった．また、バルサルバ洞内の弁輪付根部の最大流速は0 degと比較して顕著に小さいことが明らかになった．本研究から、経カテーテル弁と生体弁のコミッシャーが一致しない場合，バルサルバ洞内の弁輪付根部近傍に血流停滞が生じる知見が得られ，血栓形成に影響を及ぼす可能性が示唆された．</p>

<p>先進技術の結集からなる医療機器は、これまで治療が困難であった患者さんの治療、そして、医療の発展に大きく貢献している。革新的医療機器の開発の成功確率が高いとは言えず長い開発期間を要する。最先端の医療機器を開発し、患者さんに迅速に届けるためには、技術開発に加え、安全性と期待される有効性の科学的・合理的評価が必須である。しかし、既存の評価方法では、新しい医療技術の評価に限界があり、そのまま患者さんによる臨床試験を行なう場合にはリスク予測が困難になる問題に直面する。我々は、病態のモデル化技術を実験・シミュレーション技術を発展させ、患者を模したこれまでにない試験システムを開発して有効性と安全性の評価方法の開発に取り組み、開発の効率化、そして、行政における決断の科学的根拠に活用される研究を推進している。また、特に医療機器では医師の治療手技も治療成績向上に重要であり、治療方法がない患者さんに対する効果的治療法の開発に取り組んでいる。現場の最前線で治療に挑んでいる医師との多くの共同研究により明日の実臨床を良くする研究成果を積み上げており、本講演では、最新の我々の取り組みについて紹介する。</p>

<p>講演者が、本会の生田幸士大会長と、「真の医工連携に必要なこと」に関して意見交換したのは、今から10年以上前である。写真だけを見て仲人の勧めを信じて結婚を決意するような「戦前の見合い」方式では、相手のことがわからず、成果が上がらない、やはり、「一つ屋根の下での同棲生活」でお互いが理解でき、成果が上がりやすいのではないか、との結論を得た。そのコンセプトが、早稲田大学と東京女子医科大学の連携施設であるツインズの創設につながっている。しかし、工学研究者が第一線の臨床医と組んで高い技術を造り上げたとしても一般治療として定着するまでには多くのハードルがある。そこを乗り越えるためには十分な科学的根拠を取得することであり、医療レギュラトリーサイエンスという学問が重要となる。2014年制定の「医薬品、医療機器等の品質・有効性・安全性の確保に関する法律」が、5年を経て、新医療機器の迅速な臨床応用に向けて、さらなる法整備が進められている。その流れの中で、実臨床になるべく近い環境を再現した上で、新たな治療の効果と適正な使用法を説明できるような評価系技術の確立がキーとなり、それを体験できる人材の育成を進めている。</p>

<p>先進的医療機器や有効な治療技術が適正な開発費で開発され、患者に迅速に届けられることが日本のみならず世界で期待されている。医療機器開発においては、期待される効果の評価と合わせ、患者適用時のリスクを抽出し、評価、低減していくことが重要となる。開発する医療機器の性能を最大化させ、リスクを低減するためには、患者の解剖や背景、使用法の影響を良く検討する必要がある。First inHuman 等の先進的治療機器であるほど、承認取得のための治験は、患者の症例選択、症例数、評価期間等の点で限定的にならざるを得ない。そこで、我々は、先進的医療機器の開発を迅速化し、また、世界に先駆けて日本の患者に届ける環境を創るために、安全性と有効性の評価、そして意思決定の根拠となる、これまでにない実臨床を踏まえた非臨床試験法の開発に挑戦し、全国の医療施設と未来の医療を創造する医工学研究に取り組んでいる。また、国内外の医療機器企業等とプロジェクトを推進し、市販前には、デバイスの開発、承認申請の根拠となる実臨床を踏まえた先進的非臨床評価、また、市販後には、明日の医療に役立つ効果的な使用法の提示や、課題の迅速究明、改良の迅速化に寄与する医工学研究を推進している。合わせて、先進的医療機器の評価指標に関わるガイダンスの策定や、JIS、そしてISO 規格策定にも取り組み、先進的非臨床評価のグローバル社会への実装を推進している。</p>

<p>早稲田大学と東京女子医科大学の共同研究は、1965 年から榊原仟女子医大教授（心臓外科）と、土屋喜一早大教授（機械工学）により開始された。その後、2000 年の学術協定の正式締結により、学際型大学院の生命理工学専攻の開設、連携研究教育施設（ツインズ）の創設がなされた。さらに、大学設置基準等の省令改正を受けて、共同大学院（共同先端生命医科学専攻が我国で最初に認可され、2010 年春に開講した。当該専攻は、博士課程のみ（定員10 名）で、定員充足率は100％を超え、医療レギュラトリーサイエンス（RS）にかかわる博士論文を仕上げた42 名に対して博士号が授与された。博士の学生は、官13％、学21％、グローバル企業45％、ベンチャー企業9％であり、出身学部は、医学、理工学、薬学のみならず、獣医学、畜産学、農学、経営学、商学、経済学、法学など多彩である。したがって、博士論文の内容は、RS にかかわると言っても多岐にわたり、内容に合致した論文掲載誌を探すのにも手間がかかる。また、RS に関して様々な経験を有する８人の教員全員で毎月の進捗をチェックしているが、この研究指導をもとにRS のオリジナリティー、価値をどこに求めるかを決めるプロセスに多大な時間を要する。しかし、本専攻の学位取得者は、医療界における人脈が拡がり、産官学協議の場や製品開発、臨床研究等においてRS の適応の機会が増加しているという。また、本専攻を中核としたネットワーク形成（早稲田RS 研究所の開設）も進められている。</p>

<p>医薬品や医療機器の実用化には、綿密な前臨床試験、臨床研究・治験などが義務づけられ、動物や人間で安全性と有効性をしっかり確認することが求められている。しかし、急激な医療技術の進歩に評価試験の方法論が十分対応できていないことに加えて、最大の問題は、産官学、そして患者と、多岐にわたる利害関係者間での価値判断の基準を調整することの難しさにある。この問題に総合的な視点で取り組み、生命医科学や医療工学の基礎に基づく先進医療のガイドライン策定から、専門人材育成にまで取り組むために、2015年、早稲田大学医療レギュラトリーサイエンス(RS)研究所を創設した。一方、文部科学省の大学設置基準等の省令改正を受けて、早稲田大学と東京女子医科大学は、先進医療技術の急速な進歩を背景に、医療レギュラトリーサイエンス(RS)の博士人材育成を目指した共同大学院（共同先端生命医科学専攻）の設置申請を行い、我国初の認可を受けた。当該専攻は1学年定員10名の博士課程のみの専攻で、2010年に開講した。定員充足率は100％を超え、今までに42名に対し博士号が授与されている。本専攻の博士学位取得者のアンケート結果によれば、RS専門家としての自覚のもと、産官学や国際展開の協議の場、製品開発・臨床研究の実施の機会が増加しているという。また、医療業界の人脈の広がりにより、本専攻卒業生を中核としたネットワーク（早稲田RS研究所）の発展を推進している。</p>

&lt;p&gt;先天性心疾患治療でのFontan循環の血行動態改善を目的として心外導管外部からサポートする超小型小児用肺循環補助デバイスの開発を進めている。アクチュエータは、直径100μmの形状記憶合金で、70℃の通電加熱によって最大7%収縮する。体内埋め込み時のアクチュエータ駆動によるデバイスの発熱が課題であり、デバイスの安定した運用のために熱応答の解明と排熱機構の開発が不可欠である。そこで、本研究では、デバイスの伝熱特性の解明により、ヒートパイプを応用したアクチュエータでの発熱を大血管へと排熱する冷却システムを開発するため、デバイス伝熱応答の検討および排熱機構の基本設計を行った。 現在開発中のプロタイプ補助装置を、病態モデル動物実験により生体内での駆動試験を行い、デバイス駆動時の発熱の影響を計測した。得られた結果から、デバイスに必要な冷却温度差について検討し、ヒートパイプ排熱機構の基本設計を行った。 生体内でのデバイス駆動試験の結果より、最大発熱部で45℃までの熱上昇がみられた一方で、人工血管と接する部位で温度上昇は抑えられた。デバイス本体での最大温度と体温の温度差から、ヒートパイプ設計のための封入気体の選定と封入圧を検討した。 小児用肺循環補助デバイスのためのヒートパイプ冷却装置の基礎検討を行った。今後は、血管排熱部、デバイス吸熱部を有する冷却機構を試作し、実機試験系で性能評価を進める。&lt;/p&gt;

<p>本研究の目的は高血圧患者の腎神経表面温度を抑制可能な埋込型腎神経冷却デバイスの改良である。我々は埋込型腎神経冷却デバイスのコンセプトを実現するためにペルチェ素子とヒートパイプを組み合わせた設計を行った。埋込型デバイスはa) 3.94mmの厚さと3.2mm×3.2mmの冷却面を有するペルチェ素子、b) 6mmの直径と250mmの長さを有するヒートパイプとを機械的及び熱的にペルチェ素子の放熱面に接合して作製した。また、我々はペルチェ素子の供給電力における温度変化をサーモカメラで観測し作製した冷却デバイスの冷却性能を調べた。結果として、冷却面温度はヒートパイプを用いることで制御可能な温度を示すことが示唆された。</p>

<p>小児先天性心疾患に用いられる延伸ポリテトラフルオロエチレン（ePTFE）製肺動脈弁付導管が広く用いられるようになっている。ePTFE弁は、扇状のePTFE製弁葉と、同じくePTFE製導管から構成され、弁基部の導管壁面には生体のValsalva洞の構造を模したbulging sinusが設けられている。本研究では、ePTFE弁のさらなる性能向上を目的として右心の低圧環境下での弁葉挙動を詳細に観察・評価可能な新たな弁葉挙動試験系の構築を行った。リニアアクチュエータ、弁葉固定導管部、リザーバからなる加振試験系を構築し、弁葉形状評価のため0.1 mm厚のePTFEシートより形状の異なる2種の弁葉モデルを作製した。アクチュエータの加振は変位量、速度、加速度を任意に調整することができ、リザーバ底面に設置した高速度ビデオカメラによって加振時の弁葉挙動を取得した。構築した加振試験系を用いて2種の弁葉モデルでの挙動観察が行えた。弁尖部形状は閉鎖時の弁尖接合の状態を改善させる有効なパラメータである可能性が示唆され、本研究の展開によりePTFE弁の形状最適化が行いうる。</p>

<p>嚥下機能の評価は嚥下造影検査、反復唾液嚥下テスト、聴診所見などによって行われている。これらの機能性評価は、外部からの詳細を観察することによって行われる。嚥下挙動時には、味覚や食味といった感性要因も作用する。本研究では、食物の性状や特性が及ぼす嚥下時の咽喉挙動の変化を非接触画像解析で行い、食味食感を嚥下動作中に解析した。深度情報取得が可能な非接触カメラを用いて食物摂取時の咽喉部を外部から計測し、得られた深部情報を含む動画像を解析し、咽喉部皮膚表面形状の変化から嚥下動作の検出を試みた。健常成人を対象として、室温の飲料水と生理食塩水の飲水時の嚥下挙動を観察した。さらに、パンのペーストとしてオリーブオイルおよび調整した食用ゼラチンを塗布した食品サンプルの摂食時の嚥下挙動を非接触で計測した。計測した3次元深度画像情報を解析し、対象領域について15fpsの深度変化を調べ、咽喉部皮膚の形状変化が嚥下動作と一致する結果を得た。さらに、嚥下動作に伴う咽喉部皮膚の形状変化を周波数解析し、摂食時の流動性と官能評価に基づく食味に対して、嚥下挙動の変化の検出を定量的に示しうることが示された。</p>

ステントグラフト治療を受けた患者の長期予後を改善するため、ステントグラフト留置による心血管機能への影響を調べ、遠隔期に起きる心血管イベントとの関連について検討した。大型実験動物(ヤギ/日本ザーネン種)を対象に、ステントグラフト挿入術を行い、留置前後の心血管機能のパラメータを測定した。また、留置部位(胸部:近位と腹部:遠位)による血管機能パラメータの変動における違いについて検討した。その結果、使用したヤギは9頭(近位留置例5例、遠位留置例4例)であった。遠位および近位にステンドグラフトを留置した時の前後の左室圧波形と大動脈血流速度波形の変化は、遠位留置例で増大する傾向を認めた。収縮早期及び収縮末期における平均仕事量を算出したところ、収縮期末期において、遠位留置例で増加傾向を認めた。

<p>Fallot四徴症などの先天性心疾患に対する外科的治療の長期予後は著しく改善してきた。これらは外科的治療戦略の進化に伴うものが多く、国内での臨床例はePTFE製人工血管を用いたTCPCの方法で単一心室の心臓-血管系の力学的相互作用について安定した血行動態を維持できることを示している。</p><p>一方、長期にわたるTCPCの予後で、近年Fontan循環の遠隔期に肝機能障害などの末梢臓器不全が示唆されている。Fontan循環では、右心系血液循環での心臓の血流逆止弁がなく、肺動脈の圧力変動にともなって下大静脈へ逆流が生じることが知られている。</p><p>そこで、小児先天性心疾患のFontan循環を受動的に改善する新しい埋込型システムを考案し、呼吸などによって変動する肺動脈-下大静脈の血行力学的相互作用による逆流のみを選択的に抑制する装置の試作を試みている。</p><p>本研究では、これらの開発する埋込型能動式Fontan循環抵抗変動デバイスの試作評価に必要な肺循環抵抗変動を生成可能なFontan循環静脈系シミュレーションモデルの開発を目的として、生体胸腔内圧変動を模擬できる肺循環抵抗系の駆動システムを持つ管路系を設計した。今後、Fontan循環の抵抗変動デバイスを本低圧系循環シミュレーションモデルで評価し、長期埋込型システムの有効性と有用性を調べてゆく。</p>

<p>先天性心疾患での肺動脈狭窄に用いられるePTFE製肺動脈弁付導管の形状最適化をすすめている．本研究では，導管壁面にもたせた生体肺動脈基部のバルサルバ洞様のbulging sinusに着目し，その最適形状決定を目的として模擬循環での血行力学評価を行った．</p><p> 小児右心模擬循環回路は空気圧駆動右心房・右心室モデル，試験弁観測チャンバ，弾性肺血管・末梢血管抵抗モデル，静脈リザーバからなる．モデル循環圧・流量は小児右心循環の正常範囲内とし，収縮期間はそれぞれ心周期に対して15，40%，ポンプ拍動数は60，120 bpmとした．bulging sinusの深さの異なる3種（without，shallow，deep）の18 mm径ePTFE弁付導管をそれぞれ回路に接続し，作動流体には常温生理食塩水を用い，弁前後圧・流量を計測した．圧・流量データから収縮期弁前後エネルギー損失を算出した．また，高速度ビデオカメラを用いて弁葉挙動を取得し，弁開口面積の時系列変化を算出した．</p><p> 模擬循環での血行動態計測から，より深いbulging sinusを持たせたePTFE弁において損失エネルギーが低値を示した．また，deep bulgingの存在によって弁開放時流路面積が拡大し，弁閉鎖応答特性が向上した．ePTFE製肺動脈弁付導管の形状改良のため，設計パラメータとしてbulging sinus形状に着目し血行力学的効果の定量的評価を行った．本研究の展開によってePTFE弁改良の方向性を決定しうると考えられる．</p>

<p>現在我々は、小児先天性心疾患患者のFontan循環を補助する体内埋込み型肺循環補助装置の開発を進めている。形状記憶合金（SMA）繊維をアクチュエータとして応用し、Fontan循環での心外導管外周部に巻き付け、外部から拍動収縮する構造である。これまでに、生体での評価試験系構築のために健常成山羊を用いたFontan循環動物実験モデルを構築した。本研究では、生体内でも有効に収縮駆動可能なデバイスの構造を設計試作し、駆動試験を行い収縮特性と有用性の評価を行った。アクチュエータとして用いるSMAファイバは、通電加熱により約5-7％収縮する特性を持つ。収縮量を増幅するために、有効な拍動を行う部位と収縮量を得るスリーブ部の構成とした。滑り性が高く耐熱性のあるPTFEチューブにSMAファイバを通すことで、収縮を阻害しにくくした。スリーブ部には、ガラスファイバー製のスリーブを用い、長軸方向に収縮しにくい構造とし、拍動部にはシリコーンチューブを使用し有効な収縮と絶縁性を有する構造とした。試作したデバイスを用いて収縮駆動試験を行った。電極接続部には、シリコーン樹脂で包埋し、絶縁性を持たせた。体内埋め込み時の収縮特性試験の結果、長軸方向に巻き付け部の25%に相当する有効な収縮を得ることができた。また、Fontan循環動物モデルで小児用肺循環補助デバイスの駆動試験を実施し、体内埋め込み時にもデバイス付与によるFontan循環補助の可能性が示唆された。</p>

<p>食道癌患者の治療のための能動型人工食道の研究開発をしている。一般的には開胸開腹を必要とする外科的治療である胃管吻合術が行われている。人工食道の開発では、生体食道の蠕動運動を高度に模擬することで、流動停滞のない食物嚥下を支援することが必要であり、本研究では生体食道の詳細な力学的特性解析を行い、人工食道の設計基礎となる非線形モデルの構築を試みた。健常成ヤギから摘出した新鮮食道を用いて、引っ張り試験を行い、その結果を用いて、構築した三要素モデルを用いて応力ひずみ関係を調べた。</p>

In the development of total artificial heart (TAH), we must design left and right pumps separately to achieve a proper flow balance. In this study, we designed a motor of pump to maintain right heat circulation and prototyped. The Motor was designed by using Assumptive Magnetic Flux Path Method. We made equivalent circuit by this method, and evaluated synthetic reluctance, magnetic flux of gap for the purpose of inhibiting magnetic saturation. We adopted structure of DC brushless, four poles and 12 slots. We assumed the pump efficiency was 50%.We set maximum amount of cardiac output was 10L/min, maximum pressure was 20mmHg when rotation number was 3000rpm.In measurement, we examined the effect of gap difference, we changed the gap was 1.0 mm and 1.5 mm respectively. Result of measurement, torque and speed constants was 55 mNm/A and 180 rpm/V, 51 mNm/A and 198 rpm/V when the gap difference was 1.0 mm and 1.5 mm respectively. We confirmed the characteristics of the motor tend to high torque when the gap is narrow. On the other hand, it tends to high revolution when the gap is wide.

The authors have been developing a pulmonary mechanical simulator in order to establish a design parameters of a novel artificial cardiovascular devices. In pulmonary circulation, interactive pressure-flow changes are regulated by pulmonary impedance characteristics. We focused on the native impedance characteristics variation in the pulmonary circulation. To examine the effect of respiratory control on pulmonary resistance, we measured pulmonary arterial pressure and flow in adult goat under the different respiratory settings with open/closed-chest condition. Pulmonary input impedance in two respiratory conditions under the anesthetized open-chest positive pressure ventilation (PPV) and the awake spontaneous respiration (SR) were calculated. Longitudinal impedance at 0 Hz in SR showed lower than in PPV, and at high harmonic area in SR was bigger than in PPV. In order to examine the hemodynamic response for newly designed artificial internal organs, pulmonary impedance variation caused by respiratory control should be considered. For sophisticated pulmonary resistance model, reproducing the negative pressure condition in the thoracic cavity, and pulmonic vascular resistance regulation might be required.

Fontan procedure is the final palliative surgical operation in pediatric patients with congenital heart disease. After Fontan procedure, there is non-pulsatile flow in the pulmonary circulation. We have been developing the pulmonary circulation assist device for the Fontan circulation using shape memory alloy fibers. The device structure is mechanically contraction from the outside of the extracardiac conduit. For clinical application of the device, we have been also developing the animal experimental model for in vivo examination of the Fontan circulation assist device. In this study, we examined the hemodynamics change in the device driving the animal experimental model. The animal experimental model was constructed in four adult goats (45.8&plusmn;15.6 kg). The right heart bypass of inferior vena cava to pulmonary artery was constructed by using extracardiac conduit, and the left ventricular assist device was connected to reduce of left ventricular load. The device could be mounted easily to the conduit in the thoracic cavity. The pulsatile flow could be generated in the pulmonary circulation by the device contraction. We performed the evaluation of the pediatric pulmonary circulatory assist device in the animal experimental model.

Congenital heart disease as represented by Tetralogy of Fallot (TOF) and Transposition of great arteries may be dysfunction at right heart circulation.Surgical procedure for these cardiac arrest using pulmonary valve made from ePTFE is attracting attention. Clinical result in Japan, surgical procedure using pulmonary valve made from ePTFE is better than using biological valve in terms of thrombus formation and calcification. In order to design this valve, we need know behavior of valve cusp made from ePTFE. This valve is widely applied to clinical site and needed high-performance and high-durability. In this study, we discuss objective assessment for reduce right heart strain by improving pulmonary regurgitation base on high-precision analysis of valve cusp behavior. We manufacture reciprocating motion apparatus for analysis of valve cusp behavior under any flow condition and certain pressure load and studied mechanical characteristic of valve.

There have been demands for improving the level of activity of daily life for the patients with serious esophageal cancer. We have been developing an artificial esophagus by using Ni-Ti shape memory alloy fiber for those patients. The total installation of the device could replay the natural form of food delivery from the mouth to the stomach. In this study, we paused on the interaction control of the deglutition artificial esophagus motion by the natural trigger of the deglutition. Firstly, we made a synchronization system for swallowing required by the sensing of the throat skin acceleration. Then, we examined the sensing activity of swallowing motion detection. We performed an animal experiment to measure the surface motion caused by the deglutition using the accelerometry sensor attached to the goat throat. Secondly, we implemented an additional wireless formation in the sensing system in order to achieve the transcutaneous motion synchronization less invasively. As a result, the system developed in this study exhibited the capability of sensing by the accelerometry of swallowing motion for the sophisticated functional design for a totally implantable artificial esophagus.

Peripheral nerves transmission block is an important technique for neurophysiology and biomedical studies. For example, it is known that hypertension is contributed to by enhanced activity of the sympathetic nerve tension based on the generic preposition. Recently, development of renal sympathetic denervation (RSDN) enables us to inhibit renal sympathetic nerve activity (RSNA) by removing renal nerve as hypertensive therapy. The approach using RSDN shows that it is very much therapy, but its long-term safety and effectiveness is still under study. Up to now, we have been working in research and development of a technique that provides a quickly initiated and reversible nerve transmission block. In this study, we developed a prototype renal sympathetic cooling device that can block nerve transmission. This device can be inserted through a catheter and has a structure to be placed around renal nerve. It consists of a Peltier element that cooling area is 2.36 mm &times; 2.38 mm, and a heat sink at heat dissipation surface. For the purpose of its feasibility study, we evaluated the effectiveness of nerves cooling to block nerve transmission without producing nerve &ldquo;onset response&rdquo; firing in animal experiments.

The authors have been developing a pulmonary mechanical circulatory system in order to establish design parameters of newly designed artificial cardiovascular devices. In the quantitative examination of heart valves in pulmonary mock circulation, interactive changes in pressure and flow are regulated by pulmonary impedance characteristics. We focused on the native characteristics changes in impedance in the pulmonary circulation. <BR>To obtain the effect of respiratory control on pulmonary resistance, we measured pulmonary arterial pressure and flow in adult goat under the different respiratory settings with open- and closed-chest condition.<BR>We calculated pulmonary input impedance in two respiratory conditions under the anesthetized open-chest positive pressure ventilation (PPV) and the awake spontaneous respiration (SR). Longitudinal impedance in SR showed lower than in PPV. Characteristic impedance in SR was bigger than in PPV. Therefore, we concluded that the pulmonary impedance should be considered for more sophisticated simulation of pulmonary circulatory support devices.

In order to promote the pulmonary circulation after Fontan procedure, we have been developing a pediatric pulmonary circulatory assist device using shape memory alloy (SMA) fibers. In this study, we developed the sensorless control system for the pulmonary circulatory assist device and examined its fundamental functions. The SMA fiber shows a linear relationship between the internal resistance and longitudinal contraction. We measured a change in current of the fiber during the operation. After driving, the current was 1.8A rises from 1.4A due to contraction of the fiber, and peak value was measured at the complete contraction. We could be achieved monitoring of the contractile condition by the current change. It was indicated the system could be reduce of overheating and decrease in contractile force of the device. In the application of the control method, the high-reliability system as the implantable device might be achieved.

In order to promote peristaltic function in the patients with the end stage of esophageal cancer, we have been developing an implantable artificial esophagus. Surgical treatments, such as gastroesophagostomy, are applied for alternative reconstruction in the patients, however, the peristaltic motion will be eliminated. In this study, we focused on the distributed function in the native esophagus and examined stress-strain characteristics from proximal to distal portion using freshly extracted goat's esophagus. Prior to the measurement, we developed a new tension test apparatus. As a result, we could evaluate the circumferential esophageal characteristic variations. Then it was suggested that the circumferential stress analysis might be useful for more sophisticated design of artificial esophageal specifications, which would be consistent with the physiological demand as well as the passive structural effects.

We have been developing several variations of circulatory assist systems based on nano or micro engineering technologies. One of the special features on the design of these new styles of circulatory assist devices will be a passive controllability according to the native signal transmission and hemodynamic response. In this study, we presented the design features and the research diversity for the development of passive-active circulatory support systems, such as artificial myocardial assist devices, circulatory valves, epi-cardial or vascular support systems.

Stress is an important factor when we consider responses in the cardiovascular and the autonomic nervous systems. After ethical committee allowance, responses in the cardiovascular system and autonomic nerve were evaluated with the individual characteristics. We investigated relationship between responses to the stress and individual characteristics. Healthy adult participants were assessed with type A scale, Beck depression scale, Hostility scale and Japanese Coronary-prone Behavior Scale (JCBS). Participants were showed hateful images and performed a mathematical task (Sudoku). Heart rate (HR), systolic blood pressure (SBP), LF/HF and pulse wave transmission time (PTT) were measured. The maximum value of the cross-correlation coefficients between BP and HR (&rho;max BH), BP and PTT (&rho;max BT) were analyzed. In both tasks, higher type A scored groups had larger LF/HF, suggesting that the individual characteristics were correlated with the autonomic nervous system. Significant correlation between the Beck depression score and the decrease in PTT and the increase in BP during hateful images were observed. High type A scored or high depression level had the relationship with the stress.

広く普及している冠動脈ステントをはじめとした血管内治療機器では、病変血管内における機器展開時の生体血管との力学的均衡が重要となるが、そのバランスが崩れれば血管損傷や破裂をきたす。本研究では、流れの可視化に用いられる粒子画像流速計測法を応用して、微小蛍光粒子を添加した透明弾性血管モデルへの機器留置時のひずみ分布を高精度に定量化する手法を確立する。また、計測系の発展により大血管から細径血管まで広く用いられる治療機器の評価に適応可能な空間分解能を実現し、血管内治療機器におけるリスク分析や適正使用に資する情報を臨床現場へ提供することを目的とする。

研究代表者（梅津）の40年間にわたる“血液循環シミュレータ”開発の総仕上げとして、従来の約1/6 のスケールで新鮮血を循環させる“超小型血液循環シミュレータ”の開発を目指す。2つの新規医療機器（冠動脈用ステントおよび塞栓コイル）それぞれを開発中のシミュレータに挿入し、その機器性能が患者に使用した際の状況と限りなく近づくまでシミュレータの性能向上を図る。従来は、一巡の回路の一部を分岐させて新規医療機器の性能評価をしていたが、このミニ循環の手法により、機器ごとに血圧・血流条件を正確に設定できるので、適正使用法やリスク対応がより明確化できる。そして最終年には、厚生労働省が出す評価法ガイドライン、JIS規格、ISO規格に活用される装置の開発を目指す。これにより産官学それぞれに対して有用となる“血液循環シミュレータ”ができると考えており、新規医療機器の品質の保証、安全性と有効性確認の今まで以上に科学的根拠に基づいた方法論が確立できる。本年度は、開発した超小型血液循環シミュレータを塞栓コイルの性能試験用として活用し、シミュレータの性能を明確化することを目的として、ブタ鮮血を循環させた回路に設計の異なる3種類の塞栓コイル(以下コイル)を留置し、3次元留置形態が留置後の血流量、コイル前後の圧較差に及ぼす影響を評価した。その結果、水を用いた実験では明らかにすることができない血栓の形成を踏まえたうえでの、デバイスの設計の違いがコイル留置後の血流量の変化、コイル前後の圧較差や塞栓するまでに要する時間に影響を及ぼすことを明らかにすることができた。さらには、臨床では分析が困難である設計の違いがコイル留置部における血栓の形成と成長の仕方についても分析することができ、開発した回路の有用性を明確化することができた。

経カテーテル大動脈弁植込み術は、外科治療が困難な重症大動脈弁狭窄に対する低侵襲治療として広く行われてきているが、特有な合併症として弁輪部破裂がある。自己拡張型デバイスの導入により拡張時の弁輪損傷は低減した一方、持続的な拡張力による左室神経束の圧迫が原因となり永続的ペースメーカ留置を要する伝導障害が増加している。
本研究では、断層画像粒子流速計測法（トモグラフィックPIV）を応用し、弁留置に対する周辺血管の力学応答を高空間・時間解像度に定量計測でき、臨床での弁輪部破裂や刺激伝導系圧迫のリスク分析と解決に資する方法論として、経カテーテル大動脈弁を対象として弁留置時におけるモデル血管に生じる三次元ひずみ分布の測定法の開発を進めている。
2019年度においては、患者実形状モデルへの経カテーテル大動脈弁留置時の三次元ひずみ分布計測として、2018年度までに行った、弾性円筒モデルにおけるトモグラフィックPIVでのひずみ分布計測系と、患者実形状病変モデルとを統合させ、経カテーテル弁を留置可能な患者実形状モデルにおける弁周囲組織ひずみ分布の計測系の構築を達成できた。
構築した試験系において、基礎実験としてバルーン拡張型経カテーテル弁を患者実形状モデル内部で臨床における規定圧力で拡張留置した際の粒子移動量から算出したひずみ分布を解析したところ、石灰化部位周辺における不均一かつ突出したひずみ領域を確認することができた。
上記成果は、動的に変形する弾性体内部のひずみ計測として新たな計測手法の提案にもつながりうるものであり、医工学的にも極めて意義が大きいと考えられる。

低侵襲であることから近年増加している経カテーテル大動脈弁や冠動脈ステントといった血管内治療機器では、病変血管内における機器展開時の生体血管との力学的均衡が重要となるが、そのバランスが崩れれば血管破裂や周辺神経の障害をもたらす。
本研究では、流れの可視化に用いられる粒子画像流速計測法を応用して、微小蛍光粒子を添加した透明弾性血管モデルへの機器留置時のひずみ分布を高精度に定量化する手法を確立する。また、計測系の発展により冠動脈ステントのような細径の治療機器評価にも適応可能な空間分解能を実現し、血管内治療機器におけるリスク分析や適正使用に資する情報を臨床現場へ提供することを目的とする。
昨年度構築したシングルカメラでの二次元断面におけるひずみ分布計測技術を、2-4台での高速度カメラを用いた複数同時高速動画撮像系へと展開し、内径3 mm程度の細血管モデルに対しても高い空間分解能を得られる三次元ひずみ分布計測の実験系構築を目指す。

低侵襲であることから近年増加している、経カテーテル大動脈弁や冠動脈ステントといった血管内治療機器では、病変血管内における機器展開時の生体血管との力学的均衡が重要となるが、そのバランスが崩れれば血管破裂や周辺神経の障害をもたらす。
本研究では、流れの可視化に用いられる粒子画像流速計測法を応用して、微小蛍光粒子を添加した透明弾性血管モデルへの機器留置時のひずみ分布を高精度に定量化する手法を開発し、血管内治療機器におけるリスク分析や適正使用に資する情報の提供を目的とする。

小児の先天性肺動脈狭窄に対する右室流出路再建に用いられるハンドメイドePTFE製3弁付導管においては、バルサルバ洞形状を模した構造（bulging sinus; BS）を弁基部導管壁に持たせることで、弁開放性能の向上、収縮期エネルギー損失の低減が期待できる。しかしながら、より小児肺循環に適応するためのBS形状について、その改良のための有効な設計指針は明らかになっていない。
ePTFE製肺動脈弁付導管の形状最適化を目標とし、所有する拍動型小児右心循環シミュレータでの開放性能評価と合わせ、心収縮末期の弁葉閉鎖能に着目した静圧負荷試験による弁性能のトータル評価を実施した。オーバーフロータンクによって弁後流部側から任意の静圧を負荷できる試験装置を構築し、拍動下では観察が困難である導管壁面部の変形を高速度ビデオカメラで詳細に観測し、取得動画に対してOptical flowの手法を用いることで定量的に算出することを試みた。
研究成果の概要として、構築した試験系によるePTFE弁の弁葉周辺挙動の定量評価が行いえた。導管への圧負荷増加時には弁葉接合部よりリークが生じるが、大型のBSを持たせた導管においては直管型導管や、臨床使用されるBS付ePTFE弁と比してリーク量が増大した。Optical flow解析から、内圧上昇に伴い導管壁面のBS縫合部の径方向への拡張が観測され、弁尖接合部の間隙が大きくなることでリークが増大することが示された。これまでに実施された模擬循環回路や動物実験結果からはBSの大型化による拍動下での弁葉開放挙動の促進効果が示されているが、今後、閉鎖時の導管変形および閉鎖時リークとのトレードオフを考慮することで、弁葉およびBS形状といった設計指標の相互作用を定量的に示しえる可能性が示された。

嚥下機能の評価は嚥下造影検査、反復唾液嚥下テスト、聴診所見などによって行われている。これらの機能性評価は、外部からの詳細を観察することによって行われる。嚥下挙動時には、味覚や食味といった感性要因も作用する。本研究では、食物の性状や特性が及ぼす嚥下時の咽喉挙動の変化を非接触画像解析で行い、食味食感を嚥下動作中に解析した。深度情報取得が可能な非接触カメラを用いて食物摂取時の咽喉部を外部から計測し、得られた深部情報を含む動画像を解析し、咽喉部皮膚表面形状の変化から嚥下動作の検出を試みた。健常成人を対象として、室温の飲料水と生理食塩水の飲水時の嚥下挙動を観察した。さらに、パンのペーストとしてオリーブオイルおよび調整した食用ゼラチンを塗布した食品サンプルの摂食時の嚥下挙動を非接触で計測した。計測した3次元深度画像情報を解析し、対象領域について15fpsの深度変化を調べ、咽喉部皮膚の形状変化が嚥下動作と一致する結果を得た。さらに、嚥下動作に伴う咽喉部皮膚の形状変化を周波数解析し、摂食時の流動性と官能評価に基づく食味に対して、嚥下挙動の変化の検出を定量的に示しうることが示された。

小児先天性心疾患に用いられる延伸ポリテトラフルオロエチレン（ePTFE）製肺動脈弁付導管が広く用いられるようになっている。ePTFE弁は、扇状のePTFE製弁葉と、同じくePTFE製導管から構成され、弁基部の導管壁面には生体のValsalva洞の構造を模したbulging sinusが設けられている。本研究では、ePTFE弁のさらなる性能向上を目的として右心の低圧環境下での弁葉挙動を詳細に観察・評価可能な新たな弁葉挙動試験系の構築を行った。リニアアクチュエータ、弁葉固定導管部、リザーバからなる加振試験系を構築し、弁葉形状評価のため0.1 mm厚のePTFEシートより形状の異なる2種の弁葉モデルを作製した。アクチュエータの加振は変位量、速度、加速度を任意に調整することができ、リザーバ底面に設置した高速度ビデオカメラによって加振時の弁葉挙動を取得した。構築した加振試験系を用いて2種の弁葉モデルでの挙動観察が行えた。弁尖部形状は閉鎖時の弁尖接合の状態を改善させる有効なパラメータである可能性が示唆され、本研究の展開によりePTFE弁の形状最適化が行いうる。

本研究の目的は高血圧患者の腎神経表面温度を抑制可能な埋込型腎神経冷却デバイスの改良である。我々は埋込型腎神経冷却デバイスのコンセプトを実現するためにペルチェ素子とヒートパイプを組み合わせた設計を行った。埋込型デバイスはa) 3.94mmの厚さと3.2mm×3.2mmの冷却面を有するペルチェ素子、b) 6mmの直径と250mmの長さを有するヒートパイプとを機械的及び熱的にペルチェ素子の放熱面に接合して作製した。また、我々はペルチェ素子の供給電力における温度変化をサーモカメラで観測し作製した冷却デバイスの冷却性能を調べた。結果として、冷却面温度はヒートパイプを用いることで制御可能な温度を示すことが示唆された。

食道癌患者の治療のための能動型人工食道の研究開発をしている。一般的には開胸開腹を必要とする外科的治療である胃管吻合術が行われている。人工食道の開発では、生体食道の蠕動運動を高度に模擬することで、流動停滞のない食物嚥下を支援することが必要であり、本研究では生体食道の詳細な力学的特性解析を行い、人工食道の設計基礎となる非線形モデルの構築を試みた。健常成ヤギから摘出した新鮮食道を用いて、引っ張り試験を行い、その結果を用いて、構築した三要素モデルを用いて応力ひずみ関係を調べた。

現在我々は、小児先天性心疾患患者のFontan循環を補助する体内埋込み型肺循環補助装置の開発を進めている。形状記憶合金（SMA）繊維をアクチュエータとして応用し、Fontan循環での心外導管外周部に巻き付け、外部から拍動収縮する構造である。これまでに、生体での評価試験系構築のために健常成山羊を用いたFontan循環動物実験モデルを構築した。本研究では、生体内でも有効に収縮駆動可能なデバイスの構造を設計試作し、駆動試験を行い収縮特性と有用性の評価を行った。アクチュエータとして用いるSMAファイバは、通電加熱により約5-7％収縮する特性を持つ。収縮量を増幅するために、有効な拍動を行う部位と収縮量を得るスリーブ部の構成とした。滑り性が高く耐熱性のあるPTFEチューブにSMAファイバを通すことで、収縮を阻害しにくくした。スリーブ部には、ガラスファイバー製のスリーブを用い、長軸方向に収縮しにくい構造とし、拍動部にはシリコーンチューブを使用し有効な収縮と絶縁性を有する構造とした。試作したデバイスを用いて収縮駆動試験を行った。電極接続部には、シリコーン樹脂で包埋し、絶縁性を持たせた。体内埋め込み時の収縮特性試験の結果、長軸方向に巻き付け部の25%に相当する有効な収縮を得ることができた。また、Fontan循環動物モデルで小児用肺循環補助デバイスの駆動試験を実施し、体内埋め込み時にもデバイス付与によるFontan循環補助の可能性が示唆された。

先天性心疾患での肺動脈狭窄に用いられるePTFE製肺動脈弁付導管の形状最適化をすすめている．本研究では，導管壁面にもたせた生体肺動脈基部のバルサルバ洞様のbulging sinusに着目し，その最適形状決定を目的として模擬循環での血行力学評価を行った．小児右心模擬循環回路は空気圧駆動右心房・右心室モデル，試験弁観測チャンバ，弾性肺血管・末梢血管抵抗モデル，静脈リザーバからなる．モデル循環圧・流量は小児右心循環の正常範囲内とし，収縮期間はそれぞれ心周期に対して15，40%，ポンプ拍動数は60，120 bpmとした．bulging sinusの深さの異なる3種（without，shallow，deep）の18 mm径ePTFE弁付導管をそれぞれ回路に接続し，作動流体には常温生理食塩水を用い，弁前後圧・流量を計測した．圧・流量データから収縮期弁前後エネルギー損失を算出した．また，高速度ビデオカメラを用いて弁葉挙動を取得し，弁開口面積の時系列変化を算出した．模擬循環での血行動態計測から，より深いbulging sinusを持たせたePTFE弁において損失エネルギーが低値を示した．また，deep bulgingの存在によって弁開放時流路面積が拡大し，弁閉鎖応答特性が向上した．ePTFE製肺動脈弁付導管の形状改良のため，設計パラメータとしてbulging sinus形状に着目し血行力学的効果の定量的評価を行った．本研究の展開によってePTFE弁改良の方向性を決定しうると考えられる．

Fallot四徴症などの先天性心疾患に対する外科的治療の長期予後は著しく改善してきた。これらは外科的治療戦略の進化に伴うものが多く、国内での臨床例はePTFE製人工血管を用いたTCPCの方法で単一心室の心臓-血管系の力学的相互作用について安定した血行動態を維持できることを示している。一方、長期にわたるTCPCの予後で、近年Fontan循環の遠隔期に肝機能障害などの末梢臓器不全が示唆されている。Fontan循環では、右心系血液循環での心臓の血流逆止弁がなく、肺動脈の圧力変動にともなって下大静脈へ逆流が生じることが知られている。そこで、小児先天性心疾患のFontan循環を受動的に改善する新しい埋込型システムを考案し、呼吸などによって変動する肺動脈-下大静脈の血行力学的相互作用による逆流のみを選択的に抑制する装置の試作を試みている。本研究では、これらの開発する埋込型能動式Fontan循環抵抗変動デバイスの試作評価に必要な肺循環抵抗変動を生成可能なFontan循環静脈系シミュレーションモデルの開発を目的として、生体胸腔内圧変動を模擬できる肺循環抵抗系の駆動システムを持つ管路系を設計した。今後、Fontan循環の抵抗変動デバイスを本低圧系循環シミュレーションモデルで評価し、長期埋込型システムの有効性と有用性を調べてゆく。

There have been demands for improving the level of activity of daily life for the patients with serious esophageal cancer. We have been developing an artificial esophagus by using Ni-Ti shape memory alloy fiber for those patients. The total installation of the device could replay the natural form of food delivery from the mouth to the stomach. In this study, we paused on the interaction control of the deglutition artificial esophagus motion by the natural trigger of the deglutition. Firstly, we made a synchronization system for swallowing required by the sensing of the throat skin acceleration. Then, we examined the sensing activity of swallowing motion detection. We performed an animal experiment to measure the surface motion caused by the deglutition using the accelerometry sensor attached to the goat throat. Secondly, we implemented an additional wireless formation in the sensing system in order to achieve the transcutaneous motion synchronization less invasively. As a result, the system developed in this study exhibited the capability of sensing by the accelerometry of swallowing motion for the sophisticated functional design for a totally implantable artificial esophagus.

Peripheral nerves transmission block is an important technique for neurophysiology and biomedical studies. For example, it is known that hypertension is contributed to by enhanced activity of the sympathetic nerve tension based on the generic preposition. Recently, development of renal sympathetic denervation (RSDN) enables us to inhibit renal sympathetic nerve activity (RSNA) by removing renal nerve as hypertensive therapy. The approach using RSDN shows that it is very much therapy, but its long-term safety and effectiveness is still under study. Up to now, we have been working in research and development of a technique that provides a quickly initiated and reversible nerve transmission block. In this study, we developed a prototype renal sympathetic cooling device that can block nerve transmission. This device can be inserted through a catheter and has a structure to be placed around renal nerve. It consists of a Peltier element that cooling area is 2.36 mm × 2.38 mm, and a heat sink at heat dissipation surface. For the purpose of its feasibility study, we evaluated the effectiveness of nerves cooling to block nerve transmission without producing nerve "onset response" firing in animal experiments.

Fontan procedure is the final palliative surgical operation in pediatric patients with congenital heart disease. After Fontan procedure, there is non-pulsatile flow in the pulmonary circulation. We have been developing the pulmonary circulation assist device for the Fontan circulation using shape memory alloy fibers. The device structure is mechanically contraction from the outside of the extracardiac conduit. For clinical application of the device, we have been also developing the animal experimental model for in vivo examination of the Fontan circulation assist device. In this study, we examined the hemodynamics change in the device driving the animal experimental model. The animal experimental model was constructed in four adult goats (45.8±15.6 kg). The right heart bypass of inferior vena cava to pulmonary artery was constructed by using extracardiac conduit, and the left ventricular assist device was connected to reduce of left ventricular load. The device could be mounted easily to the conduit in the thoracic cavity. The pulsatile flow could be generated in the pulmonary circulation by the device contraction. We performed the evaluation of the pediatric pulmonary circulatory assist device in the animal experimental model.

Congenital heart disease as represented by Tetralogy of Fallot (TOF) and Transposition of great arteries may be dysfunction at right heart circulation.Surgical procedure for these cardiac arrest using pulmonary valve made from ePTFE is attracting attention. Clinical result in Japan, surgical procedure using pulmonary valve made from ePTFE is better than using biological valve in terms of thrombus formation and calcification. In order to design this valve, we need know behavior of valve cusp made from ePTFE. This valve is widely applied to clinical site and needed high-performance and high-durability. In this study, we discuss objective assessment for reduce right heart strain by improving pulmonary regurgitation base on high-precision analysis of valve cusp behavior. We manufacture reciprocating motion apparatus for analysis of valve cusp behavior under any flow condition and certain pressure load and studied mechanical characteristic of valve.

The authors have been developing a pulmonary mechanical simulator in order to establish a design parameters of a novel artificial cardiovascular devices. In pulmonary circulation, interactive pressure-flow changes are regulated by pulmonary impedance characteristics. We focused on the native impedance characteristics variation in the pulmonary circulation. To examine the effect of respiratory control on pulmonary resistance, we measured pulmonary arterial pressure and flow in adult goat under the different respiratory settings with open/closed-chest condition. Pulmonary input impedance in two respiratory conditions under the anesthetized open-chest positive pressure ventilation (PPV) and the awake spontaneous respiration (SR) were calculated. Longitudinal impedance at 0 Hz in SR showed lower than in PPV, and at high harmonic area in SR was bigger than in PPV. In order to examine the hemodynamic response for newly designed artificial internal organs, pulmonary impedance variation caused by respiratory control should be considered. For sophisticated pulmonary resistance model, reproducing the negative pressure condition in the thoracic cavity, and pulmonic vascular resistance regulation might be required.

In the development of total artificial heart (TAH), we must design left and right pumps separately to achieve a proper flow balance. In this study, we designed a motor of pump to maintain right heat circulation and prototyped. The Motor was designed by using Assumptive Magnetic Flux Path Method. We made equivalent circuit by this method, and evaluated synthetic reluctance, magnetic flux of gap for the purpose of inhibiting magnetic saturation. We adopted structure of DC brushless, four poles and 12 slots. We assumed the pump efficiency was 50%.We set maximum amount of cardiac output was 10L/min, maximum pressure was 20mmHg when rotation number was 3000rpm.In measurement, we examined the effect of gap difference, we changed the gap was 1.0 mm and 1.5 mm respectively. Result of measurement, torque and speed constants was 55 mNm/A and 180 rpm/V, 51 mNm/A and 198 rpm/V when the gap difference was 1.0 mm and 1.5 mm respectively. We confirmed the characteristics of the motor tend to high torque when the gap is narrow. On the other hand, it tends to high revolution when the gap is wide.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.In order to promote peristaltic function in the patients with the end stage of esophageal cancer, we have been developing an implantable artificial esophagus. Surgical treatments, such as gastroesophagostomy, are applied for alternative reconstruction in the patients, however, the peristaltic motion will be eliminated. In this study, we focused on the distributed function in the native esophagus and examined stress-strain characteristics from proximal to distal portion using freshly extracted goat’s esophagus. Prior to the measurement, we developed a new tension test apparatus. As a result, we could evaluate the circumferential esophageal characteristic variations. Then it was suggested that the circumferential stress analysis might be useful for more sophisticated design of artificial esophageal specifications, which would be consistent with the physiological demand as well as the passive structural effects.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.In order to promote the pulmonary circulation after Fontan operation, we developed a pediatric pulmonary circulatory assist device using shape memory alloy fibers. In this study, we developed the sensor-less control system for the pulmonary circulatory assist device and examined its fundamental functions. The SMA fiber showed a linear relationship between the internal resistance and longitudinal contraction. We measured the change in current of the fiber during the operation. Electric current increased from 1.4 to 1.8 A during operation, and the maximum current supply was measured at the end of the contraction. Therefore, we could be estimated the device contraction by the measurement of current which was calculated by voltage sampling of fiber units. Prevention of the overheating of the fiber unit was one of the problem throughout the operation of the device, and we could achieve the elimination of excess current supply by detecting the fiber voltage as well as the estimation of electric power supply without ineffective contraction. Consequently, the method in this study might be applied as a highly reliable totally implantable system.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.The authors have been developing a pulmonary mechanical circulatory system in order to establish design parameters of artificial cardiovascular assist devices. In the quantitative examination of heart valves in pulmonary mock circulation, interactive changes in pressure and flow are regulated by pulmonary impedance characteristics. We focused on the native characteristics changes in impedance in the pulmonary circulation. To obtain the effect of respiratory control on pulmonary resistance, we measured pulmonary arterial pressure and flow in adult goat under the different respiratory settings with open- and closed-chest condition. We calculated pulmonary input impedance in two respiratory conditions under the anesthetized open-chest positive pressure ventilation (PPV) and the awake spontaneous respiration (SR). Longitudinal impedance in SR showed lower than in PPV. Characteristic impedance in SR was bigger than in PPV. Therefore, we concluded that the pulmonary impedance should be considered for more sophisticated simulation of pulmonary circulatory support devices.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.Stress is an important factor when we consider responses in the cardiovascular and the autonomic nervous systems. After ethical committee allowance, responses in the cardiovascular system and autonomic nerve were evaluated with the individual characteristics. We investigated relationship between responses to the stress and individual characteristics. Healthy adult participants were assessed with type A scale, Beck depression scale, Hostility scale and Japanese Coronary-prone Behavior Scale (JCBS). Participants were showed hateful images and performed a mathematical task (Sudoku). Heart rate (HR), systolic blood pressure (SBP), LF/HF and pulse wave transmission time (PTT) were measured. The maximum value of the cross-correlation coefficients between BP and HR (ρ<inf>max</inf> BH), BP and PTT (ρ<inf>max</inf> BT) were analyzed. In both tasks, higher type A scored groups had larger LF/HF, suggesting that the individual characteristics were correlated with the autonomic nervous system. Significant correlation between the Beck depression score and the decrease in PTT and the increase in BP during hateful images were observed. High type A scored or high depression level had the relationship with the stress.

© 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.We have been developing several variations of circulatory assist systems based on nano or micro engineering technologies. One of the special features of the design of these new styles of circulatory assist devices will be a passive controllability according to the native physiological signal transmission and hemodynamic responses. In this study, we presented the design features and the research diversity for the development of passive-active circulatory support systems, such as artificial myocardial assist devices, circulatory valves, epi-cardial or vascular support systems for mechanical assistance in chronic or congenital heart failure patients. We employed a covalent type shape memory alloy fiber as the actuator for the implantable artificial internal organs for sophisticated ventricular or hemodynamic support devices.