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In the emergency care field, early treatment of acute heart or respiratory failure has been a global concern. In severe cases, patients are frequently required to be on an extracorporeal membrane oxygenator (ECMO) life support. To make the ECMO system more compact and portable, we proposed a sequential flow-type centrifugal pump named the sequential flow pump (SFP). In this study, principle and basic properties of this novel blood pump were examined by computational fluid dynamic (CFD) analysis and an experimental model. In the SFP, fluid is given centrifugal force sequentially twice with a single closed impeller. This sequential pressurization mechanism enables high-pressure output without high impeller speed. To realize easy integration of a blood pump with an artificial lung, the inlet and outlet ports are located at lateral side and center of the pump, respectively, which is the reverse configuration of conventional centrifugal pumps. The computational model was composed for CFD analysis and the experimental model was developed for the experiment of the actual pump. For both models, dimension of the impeller and volute was designed to be equal. In the CFD analysis, the SFP could generate higher performance than the single pressurization model with the same rotational speed of the impeller. Basic property of the experimental model was very similar to that of the computational model. The results showed the possibility that the SFP would be more suitable for the compact ECMO system than conventional centrifugal pumps.

Severe cardiac failure patients require a total artificial heart (TAH) to save life. To realize a TAH that can fit a body of small stature and has high performance, high durability, good anatomical fitting, good blood compatibility, and physiological control, we have been developing the helical flow TAH (HFTAH) with two helical flow pumps with hydrodynamic levitation impeller. Animal experiments of the HFTAH were conducted to perform in vivo studies. The HFTAH was implanted in 13 adult female goats weighing 45.0-64.0 kg. After surgery, neither anti-coagulant nor anti-platelet medication was given systemically. The HFTAH was usually driven with a quasi-pulsatile mode. The 1/R control or ΔP control was applied to control the circulation. The ΔP control is a new method using simplified equation of the 1/R control. The HFTAH could be implanted in all goats with good anatomical fitting. Two goats survived for a long time (100 and 68 days). Major causes of termination were device failure and surgical complications. In the device failure, trouble with hydrodynamic bearing was conspicuous. In the two long-term survived goats, experiments were terminated with bearing instability that was probably caused by the suction effect. In these goats, hemolysis occurred on postoperative day 88 and 44, which was considered to be relevant to the bearing trouble. Thrombus was found at the broken right bearing of the 100-day survived goat. However, antithrombogenicity of the pump is expected to be good unless bearing trouble occurs. In two long-term survived goats, the 1/R control or ΔP control worked appropriately to prevent the elevation of right atrial pressure. In both goats, hemodynamic parameters changed with the condition of the animals, liver and kidney functions remained almost normal except when recovering from surgery and during hemolysis, and total protein recovered 2 weeks after surgery. Although instability of the hydrodynamic bearing should be improved, performance of the HFTAH with physiological control could be demonstrated.

Animal experiments using a total artificial heart in a goat are not easy to perform. The fourth model of the undulation pump total artificial heart (UPTAH4), which was designed to perform a long-term physiological experiment including pulsatile and nonpulsatile TAH operations with a conductance- and arterial pressure-based control method named 1/R control, was implanted in 31 goats weighing 38.5 to 60.4 kg (average of 46.8 kg). The 1/R control is a physiological flow control method of TAH developed with a conductance (1/R: reciprocal of a resistance) parallel circuit model. The survival periods were from 0.1 to 153 days (average of 14.5 days). The causes of termination were postoperative bleeding in eight goats, respiratory failure in five goats, device failure in 14 goats, dissected aneurysm in two goats, and thrombus in one goat. The thrombus case was the longest surviving goat. The respiratory failure tended to occur when the extracorporeal circulation time was prolonged. Autotransfusion was effective for the prolongation of survival time. The left-right balance control and the suction control were performed successfully in all goats. The 1/R control was performed for a long time in five goats that survived for more than 1 month. With three goats that survived for 48, 52, and 53 days mainly with the pulsatile mode, the 1/R control was stable. With a goat that survived for 73 days, the nonpulsatile mode with the 1/R control could be tested for 3 weeks. With the longest surviving goat that was maintained mainly with the pulsatile mode, the 1/R control was unstable, possibly due to the mismatching of the response time of the control system between the computer and the body. However, liver and kidney functions were almost normal, and the total protein level recovered. Further study to stabilize the 1/R control in the UPTAH is necessary.

This study proposes a new type of a transcutaneous energy transmission system (TETS) that can supply electrical power for an implanted device without an external battery. In this system, the power is supplied from the floor to the shoes of the patients through coils that are set beneath the floor and the bottom of the shoes. If the patients wear the special shoes, they will be able to move freely on the specially designed floor without an external battery. Direct current (DC)-DC power efficiency was measured in the experiments, and the results showed that it varies with relative positions between the shoe and the floor coils. The results suggested that three-layered floor coils would enable the system to meet the demand for providing the required power anywhere on the floor without intermission. DC-DC power efficiency could be kept over 60% under the practical condition. It can then be concluded that the proposed system has a potential to provide better quality of life for the patients using a TETS.

A small-sized blood pump is required for a high-performance total artificial heart. From the viewpoint of the implantation, anatomical fitting into the cavity from which the heart has been removed is very important for the design of the total artificial heart. A small, high-performance blood pump is desired for a totally implantable artificial heart system. A miniaturized blood pump is not easy to achieve because of its driving mechanism and material endurance. The stroke volume is necessarily decreased by the downsizing of a volume-displacing pump, such as a sac-type blood pump. Similarly, the centrifugal force is decreased by the downsizing of a centrifugal pump. The vibrating flow pump (VFP) is one of the inertia-type pumps, but it can make a volume flow wave by its vibrating motion. The short stroke volume and high rate of driving may be notable characteristics for the minimization of the pump. In this study, a prototype VFP was made for a basic performance test. It showed adequate performance for left ventricular assistance and also showed potential for more downsizing. The estimation of the design and the driving stroke of the vibrating tube may be the next step for an advanced VFP system.

At the University of Tokyo, various types of total artificial heart (TAH) systems have been studied since 1959. At the present time, 2 types of implantable TAH have been developed. One is an undulation pump TAH (UPTAH) and the other is a flow transformed pulsatile TAH (FTPTAH). Using the UPTAH, 14 cases of implantation were performed in goats and 10 days' survival obtained. The new type of FTPTAH is under a prototype study. To prevent ring thrombus, a polyurethane membrane valve, a jellyfish valve, has been developed. The longest in vivo experiences with this valve in the TAH blood pump have been 312 days in the left side blood pump and 414 days in the right side blood pump. Conductance and arterial pressure based control (1/R control) can realize the physiological control of the TAH. Using 1/R control, 532 days of survival could be obtained in a goat with a paracorporeal TAH. The technique required to apply this control method to a implantable TAH is under development. We have proposed a new 5 year research project of the implantable TAH entitled "Comprehensive Basic Research on the Development of a Japanese Original Implantable Total Artificial Heart" to The Ministry of Welfare.

The University of Tokyo has been involved in research and development of the artificial heart since 1959. This paper is a brief review of 40 years of total artificial heart research in the University of Tokyo. Many types of artificial heart and various kinds of materials, blood pumps, valves, drive units, control methods, and pathophysiology have been investigated in our original fashion. The longest survival was 532 days for a goat with a total artificial heart (TAH) placed on the chest wall. These results made us take a step toward the development of an implantable TAH. Two kinds of implantable TAH are now being developed: FTPTAH (flow-transformed pulsatile total artificial heart) and UPTAH (undulation pump total artificial heart). Recently, a goat survived for 31 days with an UPTAH.

To obtain a physiological response by a total artificial heart (TAH), while eliminating the hemodynamic abnormalities commonly observed with its use, we proposed the use of a conductance- and arterial pressure-based method (1/R control) to determine TAH cardiac output. In this study, we endeavored to make use of a variable more closely tied to central nervous system (CNS) efferents, systemic conductance, to provide the CNS with more direct control over the output of the TAH. The control equation that calculates the target cardiac output of the TAH was constructed on the basis of measurement of blood pressures and TAH flow. The 1/R control method was tested in TAH-recipient goats with an automatic method by using a microcomputer. In 1/R control animals, the typical TAH pathologies, such as mild arterial hypertension and substantial systemic venous hypertension, did not occur. Cardiac output varied according to daily activity level and exercise in a manner similar to that observed in natural heart goats. These results indicate that we have determined a control method for the TAH that avoids hemodynamic abnormalities exhibited by other TAH control systems and that exhibits physiological responses to exercise and daily activities under the conditions tested. The stability of the control and the complete lack of inappropriate excursions in cardiac output is suggestive of CNS involvement in stabilizing the system.

The helical flow pump (HFP) was invented to develop a total artificial heart at the University of Tokyo in 2005. The HFP consists of the multi-vane impeller involving rotor magnets, a motor stator and pump housing having double-helical volutes. To investigate the characteristics of the HFP, computational fluid dynamics analysis was performed. Validation of the computational model was performed with the data of the actual pump. A control computational model in which the vane area corresponded approximately to that of the actual pump was designed for the parametric study. The parametric study was performed varying the vane height, vane width and helical volute pitch. When the vane height was varied from 0.5 to 1.5 times that of the control computational model, the H-Q (pressure head vs. flow) and efficiency curves were translated in parallel with the vane height. When the vane height was two and three times that of the control computational model, the profile of these curves changed. From the results, the best proportion for the vane was considered to be a vane height between 1.5 and 2 times the vane width. The effect of vane width was not very strong compared to that of the vane height. A similar tendency in vane height was observed by varying the helical volute pitch. The best helical volute-pitch size is considered to be between 1.5 and 2 times the vane width. Although further study is necessary to determine the best values for these parameters, the characteristics of the pump parameters in the HFP could be approximately clarified.

A total artificial heart (TAH) goat survived for 360 days on the new automatic control method (1/R control), in which the cardiac output of the TAH can be controlled through the cardiovascular center by making it function by reflecting the beta-adrenergic reaction in peripheral vascular resistance. This is thought to be the only long-term, real-time, measurable parameter by which information on the activity of the cardiovascular center can be received directly by the TAH system. In this goat, the hemodynamic parameters (RAP, AoP, and so forth) were kept within physiologic limits when control was stable, and the cardiac output was automatically increased in response to exercise, not unlike that in the natural heart. There were no abnormal blood chemical or hormone data except at end stage. Based on these results 1/R can be considered a physiologic control method for a TAH.

The role of pulsatility in a total artificial heart (TAH) has been a subject of great debate. Additionally, it is unclear whether, in non-pulsatile TAH, a physiological control method such as 1/R control can keep the animal in physiological condition or not. To examine a controllability of 1/R control in non-pulsatile TAH, non-pulsatile flow mode was introduced to the undulation pump TAH (UPTAH) and the hemodynamic parameters in pulsatile and non-pulsatile flow modes with 1/R control was analyzed. The artificial valve was removed from UPTAH and the goat’s natural heart was replaced with it. The UPTAH was first driven with a pulsatile flow mode and 1/R control was applied within one week after surgery. The pulsatile flow mode was switched to a non-pulsatile flow mode on the day 2 weeks after surgery. General condition did not change before and after the flow mode switching. Cardiac output and arterial pressure changed with the physiological condition of the goat in also non-pulsatile flow mode, which seemed not different from that in pulsatile flow mode. However, the sucking effect of atria was very significant in non-pulsatile mode. Although 1/R control could keep the animal in physiological condition in a non-pulsatile flow mode, non-pulsatile TAH was considered to be inadequate for 1/R control to stabilize atrial pressures in the present circumstances or some pulsatility would be necessary to avoid fatal sucking effect and to ensure sufficient inflow condition.

For percutaneous observation of lesions near the spinal cord and percutaneous spinal laser surgery under the visual field, we studied a method and approach to the spinal cord and intraspinal surgical procedures with laser using a newly developed, small-diameter laser endoscope. The subarachnoid and epidural spaces of a goat were punctured using a 17-gauge epidural needle, and the endoscope (diameter 0.7 mm) was inserted through the needle. The spinal cord and surrounding tissue were observed. Next, an endoscope (diameter 1.5 mm) was inserted into the subarachnoid space, and the quality of the picture and manageability of the endoscope were examined. The Xe:Cl excimer laser was irradiated to a nerve root through a 0.4 mm optical fiber for laser transmission through this endoscope. The spinal cord, nerve roots, and arachnoid were clearly observed through this endoscope. The pulsation of the artery accompanying a root was seen clearly, and the quality of the picture of the endoscope was thought to be sufficient for diagnosis. The nerve root was cut within 30 seconds by excimer laser, and the possibility of laser surgery was demonstrated. Although it was shown that this endoscope could be a useful diagnostic and therapeutic tool, improvement in the manageability of the tip of the endoscope was considered to be important for a clinically usable endoscope.

The rotary undulation pump is believed to be a good candidate for the next-generation artificial heart. Due to its complex movement, it is desirable to magnetically levitate the rotor and dynamically control the gap. In this article, the applicability of a fiber-optic gap sensor to the dynamic position control of the rotor in the rotary undulation pump was investigated. The fiber-optic gap sensor consisted of two plastic-core fibers and a reflection plate. Two 1-mm-diameter optical fibers were aligned parallel: one for source light propagation and the other for reflected light transmission. The basic properties of gap sensors using four different light sources were explored in five media (air, physiologic saline, and blood samples with three different hematocrit levels). The influence of the oxygen saturation level in the blood on sensing was investigated with two types of light sources. It is desirable to use a light source the wavelength of which shows similar absorption coefficients for both oxygenated blood and deoxygenated blood. The effect of the distance between the two fibers on the sensing and range was also investigated. The results indicated that the fiber-optic gap sensor is quite promising for the active control of rotor positioning in the rotary undulation pump.

The rotary undulation pump, which is composed of a disk with a convex shape on both sides and a pump housing with one narrow side and one wide side, is a unique continuous flow pump with a new principle. The concept of the levitation drive method for this pump was proposed. The electromagnetic driver model and drive circuit were developed to examine the possibility and the difference among the delta wired, Y wired, and repulsion methods. In the repulsion method, the disk was driven by magnetic repulsion. The model could be driven with either method, and the repulsion method was demonstrated to also be possible. With either method, owing to the wide gap between the permanent magnets and coils, the output was not enough when the load was high. The efficiency was almost the same in the delta wired and Y wired methods. In the repulsion method, however, it was less than 50% of that in the other two methods. From the results, the delta wired and Y wired methods with an active control of the gap distance were considered to be better than the repulsion method, which required no active gap control.

The undulation pump total artificial heart (UPTAH) is a unique, implantable, total artificial heart (TAH) that uses undulation pumps. To achieve long-term survival in animals with physiologic hemodynamic conditions, a control method based on conductance and arterial pressure was applied to UPTAH. With this control method, called 1/R control, survival periods of 50 days (No. 0016, 49.6 kg) and 54 days (No. 0030, 42.5 kg) were obtained in adult female goats. In No. 0016, 1/R control was applied to the left pump, whereas in No. 0030, it was applied to the right pump. Another pump was used for left-right balance control. The control stability was better in No. 0030 than in No. 0016. The sucking effect of the left atrium was remarkable in No. 0016, possibly because of a time delay when left-right balance control was performed with the right pump. In No. 0016, the cause of death was probably a thrombus flown from a panus in the left atrium. It is possible that the left atrial suction effect influenced the thrombus and panus formation in the left atrium. In No. 0030, the cause of death was a small rupture of the membrane in the right pump. The rupture may have been caused by excessive negative pressure inside the pump. This pressure resulted from suction of the right atrium because of an unexpected control excursion, which was probably caused by a software bug. It will be necessary to redesign the undulation pump and improve the software to achieve longer survival periods for animals with physiologic hemodynamic conditions.

The undulation pump total artificial heart (UPTAH) is a small implantable total artificial heart. As the UPTAH generates outflow and inflow at the same time, control of the UPTAH is very difficult. Therefore suitable control methods specifically for the UPTAH should be established. Various motor control, left-right flow balance control, and physiological control methods were examined and tried for the UPTAH control in this study. The control system is divided into seven categories. It has a hierarchical structure and all control modes work at the same time. The UPTAH with the newly developed control method has been implanted into the chest cavities of 48 goats. Until now, six goats survived for more than one month, including 63 days in the longest case. The good condition of the UPTAH implanted animal could be maintained with the newly developed control scheme, consisting of the 1/R control and several other additional controls.

An undulation pump is a special rotary blood pump in which rotation of a brushless DC motor is transformed to an undulating motion by a disc in the pump housing attached by means of a special link mechanism. In the blood pump, a closed line between the disc and housing moves from the inlet to the outlet by this undulating disc motion, which sucks and pushes the blood from the inlet to the outlet. Because the same phenomena occurs at both sides of the disc, a continuous flow is obtained when the motor rotational speed is constant. The pump flow pattern can be easily changed from continuous flow to pulsatile flow by controlling the motor drive current pattern. A seal membrane made of segmented polyurethane protects the blood from invading the link mechanism as well as the motor. UPTAH is fabricated with two undulation pumps and two brushless DC motors. Its size is 75 mm in diameter and 80 mm long, and it has one of the great advantage of no compliance chamber required in the system. UPTAHs were implanted under cardiopulmonary bypass (CPB) into the chest cavities of 16 goats, each weighing between 41 and 72 kg. No anticoagulant and antiplatelet agent was used after the surgery. The left atrial pressure was automatically controlled to prevent its elevation and sucking of the atrial wall into the atrial cuff. The following results were obtained: (1) UPTAHs fit well into all the goats; (2) the longest survival was 19.8 days, the cause of death was bleeding from the aortic anastomosis; (3) No thrombus was observed in the blood pump despite no anticoagulant use. Hemolysis depended upon the length of CPB during surgery. When CPB time was within 2 hours, hemolysis level returned to baseline within a few days of the surgery. UPTAH is a promising implantable TAH, because of its small size and easy controllability.

A conductance and arterial pressure based method (1/R control) to determine the cardiac output (CO) of a total artificial heart (TAH) was developed to provide a central nervous system with control over the output of TAH. In order to clarify the deference in hemodynamic response between natural heart and 1/R control, biventricular bypass was introduced in the goat. After 2 pneumatically driven sac-type blood pumps were connected to the natural heart, the pulmonary artery was totally clamped to acquire 100% right heart bypass, and the ascending aorta was stenosed to acquire about 60 to 90% left heart bypass; 1/R control was performed substituting the output of the right artificial heart for the CO. The results demonstrated that stable control could be achieved. A discrepancy was often seen between the pulse rate (PR) of the artificial heart and the heart rate (HR) in absolute value. However, the relative changes of PR were quite similar to that of HR for the most part, indicating that the responses of 1/R control were the duplication of natural cardiac responses in normal daily activity.

The undulation pump total artificial heart (UPTAH) was developed by using small-size continuous-flow displacement-type blood pumps (undulation pump). To clarify and improve the problems accompanied by the implantation in the chest, 14 animal experiments were performed on goats weighing 41.3-79.2 kg. The UPTAH could be implanted in the chest of all goats and was driven with a modulation pulsatile mode. The first problem was the atrial suction effect. This problem could be prevented to some extent by developing the soft disk and by improving atrial cuffs. An automatic detection and releasing of the atrial suction effect was also tried. The next problem was acute lung edema accompanied by the postural change of the animal. Development of the automatic control of left atrial pressure could prevent this problem. Small blood leakage from a pinpoint hole in the seal membrane was the next problem. Improvement of the manufacturing procedure of the membrane prevented this. With these improvements, a 10 day survival could be obtained with this unique implantable total artificial heart.

A goat survived for 532 days with a pneumatically driven total artificial heart (TAH) that was controlled by the 1/R (reciprocal of peripheral resistance) method. Pathological observations were compared with those of long-surviving goats which had been fitted with TAHs that were operated with fixed driving parameters. The most striking pathological differences were observed in the liver. In the goat under study, congestion of the liver was not as severe as in the past cases in which the central venous pressure (CVP) was high, although fibrosis was prominent around the hepatic veins in many areas of the liver. In both kidneys, severe infarctions were prominent (as in the past cases), but a characteristic of this case was the existence of marked hemosiderosis at proximal tubules; however, this was not prominent in the spleen and liver. This suggested that the hemosiderosis was due to hemolysis in the blood pump rather than due to an increased destruction of erythrocytes in the spleen and liver. The pathological improvements in the liver are believed to have been due to a comparatively low CVP (approximately 5–10 mmHg) which was achieved by the use of the 1/R control method, even though the existence of pathological abnormalities in the kidneys and liver suggested that such long-term driving of the TAH may still cause hemolysis and some damage to the liver. This point requires further investigation.

The 1/R control was developed to provide control over the output of a total artificial heart (TAH) by the central nervous system by using the peripheral vascular conductance (1/R) the vasodilatation in for the control signal. The physiologic stability of the 1/R control algorithm was tested by using goats with TAH. To apply the 1/R control equation to TAH in goats, real-time and continuous measurements of cardiac output, aortic pressure, and right atrial pressure were performed throughout the survival period. Left atrial pressure was also measured, to prevent lung edema. Under the 1/R control, 532 days’ survival was obtained in a goat with a TAH. Findings over the course of the experiment showed no hemodynamic or metabolic abnormality. Autopsy findings showed macroscopically no congestion in the liver. The experiment demonstrated the physiologic stability of the 1/R control algorithm for an extended period. Improvement of methods for measurement, such as the development of feasible techniques for the noninvasive measurement of the required hemodynamic parameters, will make it possible to use 1/R control in practice, especially for a totally implantable TAH system.

The artificial heart (AH) is already being used clinically as a bridge to heart transplantation or a circulatory assist for post-cardiotomy. However, there are, as yet, no established control methods for the AH, except for some that are very primitive. Consequently, such problems as elevation of the central venous pressure (CVP) and poor response of cardiac output to exercise still remain to be overcome.

For a valve to be fabricated seamlessly into an artificial heart (AH) blood pump, a jellyfish valve has been developed, in which a thin membrane is fixed at the center of a valve seat having several spokes to protect against prolapse of the membrane. The valve is superior in performances to a Bjork-Shiley valve, and reveals good blood compatibility. The valve would be very useful not only for AH animal study, but for future clinical use in infants to adults. Several institutions are already trying the valve. In this paper, the fabrication of the jellyfish valve is introduced, and in vitro and in vivo results summarized. A computer aided design (CAD) system was developed to cut a male wax mold of the valve seat. The input parameters to the CAD are diameter, height, thickness of rim, number of spokes, width and thickness of spokes, etc. Jellyfish valves with diameters of 4 to 27 mm have already been fabricated for many types of AHs and assist pumps.

The compliance chamber which is required for a totally implantable artificial heart, to compensate the volume change generated in a blood pump, makes it harder to implant the whole system inside a human body, for several reasons. To eliminate the compliance chamber from the totally implantable artificial heart, a new blood pump, in which no compliance chamber was required, has been designed by our group and was reported elsewhere. In this study, an actuator to drive this blood pump was developed. The mechanism of the actuator converts the rotation of the d.c. motor to linear motion of the pump diaphragm by permanent magnets without any connection. A prototype system was made and tested in a mock circulatory system. The results clarified the controversial points of the present system. However, the future feasibility of this mechanism was also exhibited.

It is desirable to use the adult goat as an experimental animal for the TAH with an implantable pneumatic driven blood pump since the calf has the problem of growth during the study period. Adult animals are also much more similar to adult human patients in physiological terms than immature animals such as the calf. However, it has not yet been possible to design a blood pump that fits well into the narrow space of the goat chest cavity. To solve this problem, a new design of the blood pump fitted to the goat chest cavity was investigated in this study. A bullet-shaped blood pump, which has two sack-type ventricles, was designed and fabricated together with a low-profile atrial cuff. The pump fitted well into goats weighing 47–67 kg and easily produced normal pump output. The results show the promise of future success in obtaining long survival with goats using this blood pump.