Itsuro Saito | The University of Tokyo (original) (raw)
Papers by Itsuro Saito
IFMBE Proceedings, 2009
... Yusuke Abe, Takashi Isoyama, Itsuro Saito, Hidekazu Miura, Hidemoto Nakagawa, Wei Shi, Yusuke... more ... Yusuke Abe, Takashi Isoyama, Itsuro Saito, Hidekazu Miura, Hidemoto Nakagawa, Wei Shi, Yusuke Inoue, Sachiko Yamaguchi, Ayumi Kishi, Minoru Ono ... No significant changes were observed both in the liver function as well as the kid-ney function between the pulsatile mode ...
Scientific Reports, 2020
Early detection of compromised circulation is essential for postoperative monitoring of free flap... more Early detection of compromised circulation is essential for postoperative monitoring of free flap. Hourly clinical check-ups such as inspection and palpation still result in a delay in detection. Conversely, optical reflection and temperature measurement are useful alternatives for detecting blood circulation. However, conventional methods that verify ischemia and congestion within a short period have not been reported. In this study, we measured short-term changes in optical reflection and temperature in a rat flap using a wearable flexible sensor probe previously developed in our laboratory. Five ischemia and five congestion groin flap models were measured using a sensor probe and reference devices. Curve fitting was performed on transition signals to evaluate changes in signals and their time constants. The optical reflection signal decreased after venous ligation and increased after arterial ligation. The parameters of the fitted curves indicate a significant difference between ...
Scientific Reports, 2020
New laparoscopic sentinel lymph node navigation using a dedicated magnetic probe and magnetic nan... more New laparoscopic sentinel lymph node navigation using a dedicated magnetic probe and magnetic nanoparticle tracer for gastric cancer patients allows minimally invasive surgeries. By identifying the sentinel lymph nodes containing magnetic nanoparticles, patients can avoid excessive lymph node extraction without nuclear facilities and radiation exposure. This paper describes the development of the laparoscopic magnetic probe, ACDC-probe, for laparoscopic sentinel lymph node identification utilizing the nonlinear response of the magnetic nanoparticles magnetized by an alternating magnetic field with a static magnetic field. For highly sensitive detection, the ratio of static to alternating magnetic fields was optimized to approximately 5. The longitudinal detection length was approximately 10 mm for 140 μg of iron, and the detectable amount of iron was approximately 280 ng at a distance of 1 mm. To demonstrate the feasibility of laparoscopic detection using the ACDC-probe and magnetic...
Journal of Artificial …, 2008
A total artifi cial heart (TAH) using continuous fl ow pumps is promising for size reduction of t... more A total artifi cial heart (TAH) using continuous fl ow pumps is promising for size reduction of the device; however, the role of pulsatility in TAHs has been a subject of great debate. Additionally, it is unclear whether, in a nonpulsatile TAH, a physiological control method such as 1/R control can keep the experimental animal in good condition. To realize a nonpulsatile TAH with 1/R control, the artifi cial valves were removed from undulation pump total artifi cial hearts (UPTAHs), which can produce both pulsatile and nonpulsatile fl ows using a single device. The UPTAHs were implanted into 18 goats, and 4 goats survived for more than 1 month. Three weeks of long-term nonpulsatile TAH operation could be tested in the goat that survived for 72 days, and it was proved that 1/R control is possible not only with a pulsatile TAH but also with a nonpulsatile TAH. The general condition of the goat and its organ function did not change on the application of nonpulsatile mode. Cardiac output and arterial pressure changed with the condition of the goat in pulsatile and also in nonpulsatile modes, and the changes seemed almost identical. However, the sucking effect of the atria was very signifi cant in nonpulsatile mode, resulting in hemolysis. Therefore, nonpulsatile TAHs under 1/R control are considered to be inadequate unless some pulsatility can be introduced to avoid fatal sucking effects and to ensure suffi cient infl ow. During nonpulsatile operation, regular fl uctuations were sometimes found in the aortic pressure, and these were caused by the periodic sucking effect in the left atrium that was possibly infl uenced by respiratory changes.
Springer Tracts in Advanced Robotics, 2000
ABSTRACT
Asaio Journal, Jun 30, 2004
A new system to observe the microcirculation on the bulbar conjunctiva was developed using a digi... more A new system to observe the microcirculation on the bulbar conjunctiva was developed using a digital high definition microscope to investigate the influence of the flow patterns on the microcirculation in a goat with a total artificial heart (TAH). The undulation pump TAH was implanted into the goat. When the whole body condition became stable, the flow pattern was modulated between the pulsatile and the nonpulsatile mode, and the changes in the microcirculation were observed. When the flow pattern was changed from pulsatile to nonpulsatile mode, the erythrocyte velocity in capillaries dropped from 526+/-83 to 132+/-41 microm/s and remained at a low level. The number of perfused capillaries decreased as well. Then the nonpulsatile flow mode was maintained for 20 minutes. After the flow pattern was returned to the pulsatile mode again, the erythrocyte velocity recovered to the initial level (433+/-71 microm/s). In many cases, the flow of the nonperfused capillaries in the nonpulsatile mode recovered to the initial level after the flow pattern was changed to the pulsatile mode again. The perfused capillary density in the nonpulsatile mode (19.7+/-4.1 number of capillaries/mm) was significantly lower than that in the pulsatile mode (34.7+/-6.3 number of capillaries/mm). It is thought that the basal and flow stimulated endothelium derived nitric oxide release in the microvessels decreased because of the disappearance of pulsatility and that the nitric oxide induced the constriction of arterioles after the flow pattern was changed to the nonpulsatile mode. At the same time, the baroceptors might sense the decrease in the arterial peak pressure or dp/dt, and the sympathetic nerve increases activities and induce the constriction of arterioles. Then, the erythrocyte velocity in capillaries would decrease. Because of the flow pattern further in the chronic phase, it is important to follow the change in the microcirculation.
Asaio Journal, Jun 30, 2000
An undulation pump is a special rotary blood pump in which rotation of a brushless DC motor is tr... more 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.
ASAIO Journal
A transcutaneous energy transmission system (TETS) for artificial hearts and ventricular assist d... more A transcutaneous energy transmission system (TETS) for artificial hearts and ventricular assist devices uses electrical coupling of power between external and implanted coils. If the position of coils changes relative to each other, the TETS cannot feed the required power of the implanted device. During activity or sleep, the coils may move accidentally. TETS users and the people around them have to pay attention to this because the range of the position where the required power can be fed efficiently is not wide. Therefore, we added functions for the position changes of the coils to the TETS. Regular, cautious, and irregular positions were introduced, and the ranges of them were decided upon in our experiments. The cautious position was determined by the area where the change of the relative position of the coils was relatively small. When the coils were in the cautious position, the circuit was tuned by way of changing the resonant point. This modulation could give good power efficiency in the cautious position. When the coils were in the irregular position, an alarm switch was turned on. These functions ease the restriction of the coil position and give better quality of life (QOL) than do the conventional TETS.
ASAIO Journal
The undulation pump total artificial heart is an implantable total artificial heart that is being... more The undulation pump total artificial heart is an implantable total artificial heart that is being developed at the University of Tokyo. Many advances in our system have been made by the adoption of hardware and software solutions that enabled the animals with the undulation pump total artificial hearts to survive more than 1 month. Pathophysiologic observations were performed for these goats that survived. In this article, the pathophysiologic findings are described in detail for three goats that survived for 46 (goat 9916), 54 (0030), and 63 (0107) days. The microscopic findings indicated that in goat 0107 the histologic changes in key organs occurred at the termination of the experiments. Therefore, the pathophysiologic changes in goats 9916 and 0030 were mainly investigated in this study to evaluate the chronic effect caused by our total artificial heart system. The signs of chronic ischemia and cell dystrophy were observed in both the liver and kidney. Until now, 13 goats had survived more than 1 week and 6 goats survived more than 1 month, including one that survived for 63 days, which is the longest in our experimental series. The pathophysiologic results of goats 9916 and 0030 showed that the undulation pump total artificial heart might still cause some damage to the liver and the kidney. To accomplish long-term survival with the undulation pump total artificial heart, further pathophysiologic studies are required, and the necessary modifications to the total artificial heart system will need to be made.
Journal of Artificial Organs, 2002
The undulation pump is a unique continuous-flow displacement-type blood pump with high performanc... more The undulation pump is a unique continuous-flow displacement-type blood pump with high performance. However, the undulation pump has limited mechanical durability. To eliminate this limitation, the principle of the rotary undulation pump was developed. The rotary undulation pump is composed of a disk having a pair of convex shapes on both side and pump housing having a shape such that one side is narrow and the other side is wide. The disk nutates and at the same time rotates at half the speed of nutation. With this movement of the disk, the disk can rotate through the narrow part of the pump housing and pump mechanism occurs. Between the disk and the pump housing, four pump rooms are created. The four outputs are added at the outlet port, and continuous flow is generated. The practical shape was designed with computer graphics. The motion of the disk was calculated accurately with the computer, and the principle was confirmed. The inlet and outlet port areas were also calculated. Models were developed to demonstrate the principle. With the magnetic coupling method, up to about 6 l/min of output could be measured against 100 mmHg of pressure load, and the principle was demonstrated to work. An experimental model to study an electromagnetic drive method, including a magnetically suspended drive, is being developed for the next step. Although many objectives remain, the basic principle of the rotary undulation pump was confirmed.
The undulation pump ventricular assist device (UPVAD) is a small implantable ventricular assist d... more The undulation pump ventricular assist device (UPVAD) is a small implantable ventricular assist device using an undulation pump. The UPVAD can produce not only continuous flow but also pulsatile flow by changing the motor rotational speed of the UPVAD. Because the undulation pump is a volume displacement type pump in which the inflow action and outflow action both start at the same phase, the inflow sucking occurs easily. The purpose of this study is to develop a suitable control method for the UPVAD. The UPVAD inflow cannula equipped with an implantable blood pressure sensor is inserted into the ventricular. Therefore, pressure fluctuation that synchronizes with the natural heartbeat is observed in the inflow cannula. By changing the motor rotational speed that responds to the inflow pressure, the UPVAD can synchronize with the natural heartbeat and the UPVAD can generate either aco-pulse assist flow or a counter pulse assist flow. The newly developed control method exhibited super...
Development of an implantable artificial heart is very important to save cardiac disease patients... more Development of an implantable artificial heart is very important to save cardiac disease patients. An undulation pump ventricular assist device (UPVAD) could be a good candidate because of the compact size. Although the implantation improves patient’s quality of life (QOL) considerably, several implications hamper the development of an implantable artificial heart. The difficulty in blood pressure measurement is the one of the implications to be solved. We have developed the im-plantable absolute pressure sensor to be integrated into a UPVAD and the algorithm to infer the blood pressure referred to gauge pressure. Noble feature of the algorithm is autonomous compensation of the offset drift with the pressure sensor in time. Thus the blood pressure could be controlled precisely with the implantable UPVAD even if the pressure sensor exhibited certain drift characteristics. Animal experiment demonstrated the effectiveness in compensating the offset drift
Artificial Organs, 2015
Severe cardiac failure patients require a total artificial heart (TAH) to save life. To realize a... more 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.
Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs, Jan 18, 2015
The helical flow pump (HFP) was invented to be an ideal pump for developing the TAH and the helic... more The helical flow pump (HFP) was invented to be an ideal pump for developing the TAH and the helical flow TAH (HFTAH) using two HFPs has been developed. However, since the HFP is quite a new pump, hydrodynamic characteristics inside the pump are not clarified. To analyze hydrodynamic characteristics of the HFP, flow visualization study using the particle image velocimetry and computational fluid dynamics analysis were performed. The experimental and computational models were developed to simulate the left HFP of the HFTAH and distributions of flow velocity vectors, shear stress and pressure inside the pump were examined. In distribution of flow velocity vectors, the vortexes in the vane were observed, which indicated that the HFP has a novel and quite unique working principle in which centrifugal force rotates the fluid in the helical volutes and the fluid is transferred from the inlet to the outlet helical volutes according to the helical structure. In distribution of shear stress, ...
IFMBE Proceedings, 2009
... Yusuke Abe, Takashi Isoyama, Itsuro Saito, Hidekazu Miura, Hidemoto Nakagawa, Wei Shi, Yusuke... more ... Yusuke Abe, Takashi Isoyama, Itsuro Saito, Hidekazu Miura, Hidemoto Nakagawa, Wei Shi, Yusuke Inoue, Sachiko Yamaguchi, Ayumi Kishi, Minoru Ono ... No significant changes were observed both in the liver function as well as the kid-ney function between the pulsatile mode ...
Scientific Reports, 2020
Early detection of compromised circulation is essential for postoperative monitoring of free flap... more Early detection of compromised circulation is essential for postoperative monitoring of free flap. Hourly clinical check-ups such as inspection and palpation still result in a delay in detection. Conversely, optical reflection and temperature measurement are useful alternatives for detecting blood circulation. However, conventional methods that verify ischemia and congestion within a short period have not been reported. In this study, we measured short-term changes in optical reflection and temperature in a rat flap using a wearable flexible sensor probe previously developed in our laboratory. Five ischemia and five congestion groin flap models were measured using a sensor probe and reference devices. Curve fitting was performed on transition signals to evaluate changes in signals and their time constants. The optical reflection signal decreased after venous ligation and increased after arterial ligation. The parameters of the fitted curves indicate a significant difference between ...
Scientific Reports, 2020
New laparoscopic sentinel lymph node navigation using a dedicated magnetic probe and magnetic nan... more New laparoscopic sentinel lymph node navigation using a dedicated magnetic probe and magnetic nanoparticle tracer for gastric cancer patients allows minimally invasive surgeries. By identifying the sentinel lymph nodes containing magnetic nanoparticles, patients can avoid excessive lymph node extraction without nuclear facilities and radiation exposure. This paper describes the development of the laparoscopic magnetic probe, ACDC-probe, for laparoscopic sentinel lymph node identification utilizing the nonlinear response of the magnetic nanoparticles magnetized by an alternating magnetic field with a static magnetic field. For highly sensitive detection, the ratio of static to alternating magnetic fields was optimized to approximately 5. The longitudinal detection length was approximately 10 mm for 140 μg of iron, and the detectable amount of iron was approximately 280 ng at a distance of 1 mm. To demonstrate the feasibility of laparoscopic detection using the ACDC-probe and magnetic...
Journal of Artificial …, 2008
A total artifi cial heart (TAH) using continuous fl ow pumps is promising for size reduction of t... more A total artifi cial heart (TAH) using continuous fl ow pumps is promising for size reduction of the device; however, the role of pulsatility in TAHs has been a subject of great debate. Additionally, it is unclear whether, in a nonpulsatile TAH, a physiological control method such as 1/R control can keep the experimental animal in good condition. To realize a nonpulsatile TAH with 1/R control, the artifi cial valves were removed from undulation pump total artifi cial hearts (UPTAHs), which can produce both pulsatile and nonpulsatile fl ows using a single device. The UPTAHs were implanted into 18 goats, and 4 goats survived for more than 1 month. Three weeks of long-term nonpulsatile TAH operation could be tested in the goat that survived for 72 days, and it was proved that 1/R control is possible not only with a pulsatile TAH but also with a nonpulsatile TAH. The general condition of the goat and its organ function did not change on the application of nonpulsatile mode. Cardiac output and arterial pressure changed with the condition of the goat in pulsatile and also in nonpulsatile modes, and the changes seemed almost identical. However, the sucking effect of the atria was very signifi cant in nonpulsatile mode, resulting in hemolysis. Therefore, nonpulsatile TAHs under 1/R control are considered to be inadequate unless some pulsatility can be introduced to avoid fatal sucking effects and to ensure suffi cient infl ow. During nonpulsatile operation, regular fl uctuations were sometimes found in the aortic pressure, and these were caused by the periodic sucking effect in the left atrium that was possibly infl uenced by respiratory changes.
Springer Tracts in Advanced Robotics, 2000
ABSTRACT
Asaio Journal, Jun 30, 2004
A new system to observe the microcirculation on the bulbar conjunctiva was developed using a digi... more A new system to observe the microcirculation on the bulbar conjunctiva was developed using a digital high definition microscope to investigate the influence of the flow patterns on the microcirculation in a goat with a total artificial heart (TAH). The undulation pump TAH was implanted into the goat. When the whole body condition became stable, the flow pattern was modulated between the pulsatile and the nonpulsatile mode, and the changes in the microcirculation were observed. When the flow pattern was changed from pulsatile to nonpulsatile mode, the erythrocyte velocity in capillaries dropped from 526+/-83 to 132+/-41 microm/s and remained at a low level. The number of perfused capillaries decreased as well. Then the nonpulsatile flow mode was maintained for 20 minutes. After the flow pattern was returned to the pulsatile mode again, the erythrocyte velocity recovered to the initial level (433+/-71 microm/s). In many cases, the flow of the nonperfused capillaries in the nonpulsatile mode recovered to the initial level after the flow pattern was changed to the pulsatile mode again. The perfused capillary density in the nonpulsatile mode (19.7+/-4.1 number of capillaries/mm) was significantly lower than that in the pulsatile mode (34.7+/-6.3 number of capillaries/mm). It is thought that the basal and flow stimulated endothelium derived nitric oxide release in the microvessels decreased because of the disappearance of pulsatility and that the nitric oxide induced the constriction of arterioles after the flow pattern was changed to the nonpulsatile mode. At the same time, the baroceptors might sense the decrease in the arterial peak pressure or dp/dt, and the sympathetic nerve increases activities and induce the constriction of arterioles. Then, the erythrocyte velocity in capillaries would decrease. Because of the flow pattern further in the chronic phase, it is important to follow the change in the microcirculation.
Asaio Journal, Jun 30, 2000
An undulation pump is a special rotary blood pump in which rotation of a brushless DC motor is tr... more 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.
ASAIO Journal
A transcutaneous energy transmission system (TETS) for artificial hearts and ventricular assist d... more A transcutaneous energy transmission system (TETS) for artificial hearts and ventricular assist devices uses electrical coupling of power between external and implanted coils. If the position of coils changes relative to each other, the TETS cannot feed the required power of the implanted device. During activity or sleep, the coils may move accidentally. TETS users and the people around them have to pay attention to this because the range of the position where the required power can be fed efficiently is not wide. Therefore, we added functions for the position changes of the coils to the TETS. Regular, cautious, and irregular positions were introduced, and the ranges of them were decided upon in our experiments. The cautious position was determined by the area where the change of the relative position of the coils was relatively small. When the coils were in the cautious position, the circuit was tuned by way of changing the resonant point. This modulation could give good power efficiency in the cautious position. When the coils were in the irregular position, an alarm switch was turned on. These functions ease the restriction of the coil position and give better quality of life (QOL) than do the conventional TETS.
ASAIO Journal
The undulation pump total artificial heart is an implantable total artificial heart that is being... more The undulation pump total artificial heart is an implantable total artificial heart that is being developed at the University of Tokyo. Many advances in our system have been made by the adoption of hardware and software solutions that enabled the animals with the undulation pump total artificial hearts to survive more than 1 month. Pathophysiologic observations were performed for these goats that survived. In this article, the pathophysiologic findings are described in detail for three goats that survived for 46 (goat 9916), 54 (0030), and 63 (0107) days. The microscopic findings indicated that in goat 0107 the histologic changes in key organs occurred at the termination of the experiments. Therefore, the pathophysiologic changes in goats 9916 and 0030 were mainly investigated in this study to evaluate the chronic effect caused by our total artificial heart system. The signs of chronic ischemia and cell dystrophy were observed in both the liver and kidney. Until now, 13 goats had survived more than 1 week and 6 goats survived more than 1 month, including one that survived for 63 days, which is the longest in our experimental series. The pathophysiologic results of goats 9916 and 0030 showed that the undulation pump total artificial heart might still cause some damage to the liver and the kidney. To accomplish long-term survival with the undulation pump total artificial heart, further pathophysiologic studies are required, and the necessary modifications to the total artificial heart system will need to be made.
Journal of Artificial Organs, 2002
The undulation pump is a unique continuous-flow displacement-type blood pump with high performanc... more The undulation pump is a unique continuous-flow displacement-type blood pump with high performance. However, the undulation pump has limited mechanical durability. To eliminate this limitation, the principle of the rotary undulation pump was developed. The rotary undulation pump is composed of a disk having a pair of convex shapes on both side and pump housing having a shape such that one side is narrow and the other side is wide. The disk nutates and at the same time rotates at half the speed of nutation. With this movement of the disk, the disk can rotate through the narrow part of the pump housing and pump mechanism occurs. Between the disk and the pump housing, four pump rooms are created. The four outputs are added at the outlet port, and continuous flow is generated. The practical shape was designed with computer graphics. The motion of the disk was calculated accurately with the computer, and the principle was confirmed. The inlet and outlet port areas were also calculated. Models were developed to demonstrate the principle. With the magnetic coupling method, up to about 6 l/min of output could be measured against 100 mmHg of pressure load, and the principle was demonstrated to work. An experimental model to study an electromagnetic drive method, including a magnetically suspended drive, is being developed for the next step. Although many objectives remain, the basic principle of the rotary undulation pump was confirmed.
The undulation pump ventricular assist device (UPVAD) is a small implantable ventricular assist d... more The undulation pump ventricular assist device (UPVAD) is a small implantable ventricular assist device using an undulation pump. The UPVAD can produce not only continuous flow but also pulsatile flow by changing the motor rotational speed of the UPVAD. Because the undulation pump is a volume displacement type pump in which the inflow action and outflow action both start at the same phase, the inflow sucking occurs easily. The purpose of this study is to develop a suitable control method for the UPVAD. The UPVAD inflow cannula equipped with an implantable blood pressure sensor is inserted into the ventricular. Therefore, pressure fluctuation that synchronizes with the natural heartbeat is observed in the inflow cannula. By changing the motor rotational speed that responds to the inflow pressure, the UPVAD can synchronize with the natural heartbeat and the UPVAD can generate either aco-pulse assist flow or a counter pulse assist flow. The newly developed control method exhibited super...
Development of an implantable artificial heart is very important to save cardiac disease patients... more Development of an implantable artificial heart is very important to save cardiac disease patients. An undulation pump ventricular assist device (UPVAD) could be a good candidate because of the compact size. Although the implantation improves patient’s quality of life (QOL) considerably, several implications hamper the development of an implantable artificial heart. The difficulty in blood pressure measurement is the one of the implications to be solved. We have developed the im-plantable absolute pressure sensor to be integrated into a UPVAD and the algorithm to infer the blood pressure referred to gauge pressure. Noble feature of the algorithm is autonomous compensation of the offset drift with the pressure sensor in time. Thus the blood pressure could be controlled precisely with the implantable UPVAD even if the pressure sensor exhibited certain drift characteristics. Animal experiment demonstrated the effectiveness in compensating the offset drift
Artificial Organs, 2015
Severe cardiac failure patients require a total artificial heart (TAH) to save life. To realize a... more 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.
Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs, Jan 18, 2015
The helical flow pump (HFP) was invented to be an ideal pump for developing the TAH and the helic... more The helical flow pump (HFP) was invented to be an ideal pump for developing the TAH and the helical flow TAH (HFTAH) using two HFPs has been developed. However, since the HFP is quite a new pump, hydrodynamic characteristics inside the pump are not clarified. To analyze hydrodynamic characteristics of the HFP, flow visualization study using the particle image velocimetry and computational fluid dynamics analysis were performed. The experimental and computational models were developed to simulate the left HFP of the HFTAH and distributions of flow velocity vectors, shear stress and pressure inside the pump were examined. In distribution of flow velocity vectors, the vortexes in the vane were observed, which indicated that the HFP has a novel and quite unique working principle in which centrifugal force rotates the fluid in the helical volutes and the fluid is transferred from the inlet to the outlet helical volutes according to the helical structure. In distribution of shear stress, ...