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Biomedical subjects

M Shiono

Publications and source records attributed to M Shiono.

At least 73 records · Page 4Linked to original sources
PubMed1993

Left and right pump output control in one-piece electromechanical total artificial heart.

Left master alternate (LMA) ejection control based on the left pump fill method was implemented for a one-piece electromechanical total artificial heart (TAH). The TAH consists of left and right pusher-plate-type blood pumps sandwiching a compact electromechanical actuator comprising a direct current (DC) brushless motor and a planetary roller screw. The motor rotation is controlled on the basis of the roller-screw position as detected by a Hall effect sensor and a commutation pulse counting method. Since the pusher-plate shaft and roller screw are decoupled during filling, both pumps fill passively with the right and left atrial pressure. To obtain response to the right atrial pressure change in the LMA mode, the left fill trigger level as detected by a Hall effect position sensor is adjusted to operate the pump at a higher rate and to drive the right pump at 85-90% of the full stroke level. The in vitro evaluation demonstrated that this method can respond to right atrial pressure changes provided that the right pump is operated at less than the full stroke level. When the preload is high and the right pump goes into full stroke operation, the left eject level can be decreased to run the pump at a higher rate and to transfer more blood from the right to the left. In the in vivo evaluation, which lasted 1 week in a 95 kg calf, the left and right atrial pressures were kept within physiological ranges.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A unique in vivo assessment of 4-[10B]borono-L-phenylalanine in tumour tissues for boron neutron capture therapy of malignant melanomas using positron emission tomography and 4-borono-2-[18F]fluoro-L-phenylalanine.

A unique in vivo approach to assessing the concentrations of 4-[10B]borono-L-phenylalanine (L-BPA), a melanoma targeting compound for boron neutron capture therapy (BNCT), was investigated using L-BPA labelled with positron-emitting 18F (half-life = 110 min), i.e., 4-[10B]borono-2-[18F]fluoro-L-phenylalanine (L-[18F]FBPA). High melanoma uptake of L-[18F]FBPA was reduced slightly by competition with L-BPA in the two animal models of the murine B16 melanoma and the melanotic Greene's melanoma No. 179 in hamsters. In mice given L-[18F]FBPA and L-BPA, the concentrations of 10B in B16 estimated from 18F radioactivity were lower than those measured by inductively coupled plasma-atomic emission spectroscopy. Lower estimated values were dependent on the time after injection and on the loading dose of L-BPA. The estimated 10B concentrations for Green's melanomas were comparable to the measured values. Positron emission tomography (PET) using L-[18F]FBPA allowed Greene's melanomas to be clearly visualized. In conclusion, when L-[18F]FBPA is used as a probe for L-BPA in BNCT of malignant melanomas, the melanoma can be localized and the 10B concentrations in tissues can be assessed in vivo using 18F radioactivity by PET.

Animals↗
PubMed1992

New sequential synchronized driving system of intraaortic balloon pumping and left ventricular assist device: influence on endocardial viability ratio and renal blood flow in their combination.

Intraaortic balloon pumping (IABP) and left ventricular assist devices (LVAD) have shown remarkable progress individually, but how to combine them is still unknown. A new sequential synchronized driving system was developed to control concomitant use of IABP and LVAD, and then its hemodynamic effectiveness was evaluated in swine, especially on endocardial viability ratio (EVR) and renal blood flow. This system (pulsatile bypass pump-delay divide system, PBP-DDS) made it possible to change the driving phase of IABP and LVAD easily. In 12 swine, IABP and LVAD were set up, and these devices were driven in the following 5 modes with the PBP-DDS: mode I, IABP alone; mode II, LVAD alone; mode III, IABP + LVAD (same timing); mode IV, IABP (early diastole) + LVAD (late diastole); and mode V, LVAD (early diastole) + IABP (late diastole). EVR was increased more markedly by combined use of both IABP and LVAD (modes III, IV, and V) than by individual drive, but there was no significant difference among these modes. On the other hand, renal blood flow was decreased so dramatically by the same timing optimal counterpulsation method of mode III that it was thought to be harmful for renal function. But, the delay divide combination method of modes IV and V resulted in no change in the renal circulation. So, it was concluded that this delay divide combination mode appeared to be a more promising support to both failed heart and renal circulation.

Animals↗
PubMed1992

Development of a totally implantable electromechanical total artificial heart: Baylor TAH.

A totally implantable, one-piece, electrome-chanical total artificial heart (TAH) intended for permanent human use has been developed. It consists of left and right pusher-plate pumps (63 cc design stroke volume) sandwiching a thin center piece with a compact electromechanical actuator. The pusher-plates are shaped conically to accommodate an actuator in the space between them. The actuator consists of an efficient and durable planetary roller screw and direct current brushless motor. The left master alternate pumping mode was implemented utilizing the left pump pusher-plate position signal. The blood-contacting surface was coated with a dry gelatin to yield long-term clot-free performance. Trileaflet tissue valves of 27 and 23 mm are used in the inflow and outflow ports. The diameter and thickness of the TAH are 97 and 82 mm. the overall volume is 510 cc, and the weight is 620 g. Anatomic fit was confirmed in 26 heart transplant recipients (body weight 78 kg and surface area 2 m2) without compressing adjacent organs. The pump performance study revealed that the TAH can yield outputs of 3-8 L/min against the 100 mm Hg afterload with 1-10 mm Hg filling pressure. The input power to the motor ranged from 7 to 12 W, with an efficiency of 18% to 14%. A one-week in vivo calf study demonstrated adequate performance of the TAH, particularly the regulation of atrial pressures. Good anatomic fit and good biocompatibility were also demonstrated.

Animals↗
PubMed1992

Development of totally implantable electromechanical artificial heart systems: Baylor ventricular assist system.

An implantable electromechanical ventricular assist system (VAS) intended for permanent use has been developed. It consists of a conically shaped pumping chamber, a polyolefin (Hexsyn) rubber diaphragm attached to a conically shaped pusher-plate, and a compact roller-screw actuator. Design stroke volume is 63 ml. The device weighs 620 g, and has a total volume of 348 ml. The pump can provide 8 L/min flow against 120 mm Hg afterload with a preload of 10 mm Hg. The inner surfaces are biolized by dry gelatin coating, with inflow and outflow ports accommodating tissue valves. Three subacute in vivo validation studies have been conducted in calves up to two weeks. The entire system functioned satisfactorily in both the fill/empty and the fixed-rate modes. There was no thromboembolic complication without anticoagulation. The pump showed reasonable anatomical fit inside the left thorax. This VAS is compact, efficient, quiet, and easy to control.

Animals↗
PubMed1992

A compact centrifugal pump for cardiopulmonary bypass.

A majority of the cardiopulmonary bypass (CPB) systems still utilize bulky roller pumps. A direct-drive small centrifugal pump intended for second-generation CPB pump has been developed. The pump has a 50 mm diameter impeller and provides a 6 L/min flow at 3,000 rpm against 300 mm Hg. A flexible drive shaft allows us to separate the pump head from the console resulting in easier manipulation. An in vitro study showed that the pump generated less hemolysis (index of hemolysis = 0.0011, comparable to the value for Bio-medicus BP-80). To improve blood flow around the shaft-seal region and to reduce thrombus formation around the shaft, six holes were drilled through the impeller. In biventricular bypass experiments using calves, our pump demonstrated excellent antithrombogenicity and durability for 48 h. And the compact and atraumatic centrifugal pump system showed excellent performance and easy manipulation under actual CPB conditions in animal.

Animals↗
PubMed1992

Development of an atraumatic small centrifugal pump for second-generation cardiopulmonary bypass.

A small and light direct-drive centrifugal pump has been developed for cardiopulmonary bypass. In the development process, blood compatibility studies including a hemolysis study, an in vitro fluid dynamic performance study, and in vivo durability and feasibility studies were performed. The centrifugal pump with a 50 mm diameter impeller resulted in almost the same index of hemolysis value as did a Bio-Medicus centrifugal pump. Heat dissipation from the motor was prevented by using a flexible drive cable. Forty-eight-hour sealing durability around the driving axis was accomplished by using a fluoro-rubber V-ring that connected to the hard chrome-plated stainless steel. In vitro and in vivo performances of the pump were satisfactory. Thrombus formation behind the impeller was prevented by using a holed impeller that generated blood flow from the back to the surface of the impeller. Elimination of air during priming procedures was also easier with this modification. This centrifugal pump has one-quarter of the priming volume, size, and weight of magnetically coupled centrifugal pump systems.

Animals↗
PubMed1992

Versatile one-piece total artificial heart for bridge to transplantation or permanent heart replacement.

A versatile, one-piece total artificial heart (TAH) system that can be driven by either an electromechanical acutator (EM-TAH) or a pneumatic source (P-TAH) has been developed. The common units for both TAHs are the conically shaped left and right pusher-plate-type pumps (63 ml SV) that sandwich a thin centerpiece (18 mm) having a respective actuator. The EM actuator, mounted in the middle of the centerpiece, consists of a direct-current brushless motor and a roller screw while the pneumatic actuator consists of a low-pressure air source. The outer diameter of the pumping unit is 97 mm with its central thickness being 82 mm; overall volume is 510 cc. The TAH is operated in the left master alternative ejection mode with the left pump fill signal. High-flex-life Hexsyn rubber is used as the diaphragm, and the blood-contacting surface is coated with dry gelatin. The TAH can provide 3-8 L/min flow with a preload of 1-10 mm Hg against 100 mm Hg afterload. Anatomical fit of the pumping unit has been demonstrated in the pericardial space of 26 heart transplant recipients with average body weight of 78 kg. To date, 2 P-TAH and 4 EM-TAH (1 week) implantations were performed in 80-100 kg calves demonstrating excellent anatomical fit, controllability, and biocompatibility. This versatile TAH is suitable for a bridge to transplantation or permanent heart replacement.

Animals↗
PubMed1992

Potential clinical applications of the oxygen carrying solutions.

Two major areas of research of the oxygen carrying solutions are 1) utilization of hemoglobin and 2) perfluorochemicals. Even though they are not perfect red blood cell substitutes, the "oxygen carrying solutions" have many potential clinical applications because they will reach tissues more easily than normal human red cells and can deliver oxygen directly to tissues. In this paper, important examples of such usages are suggested. Additional clinical and non-clinical applications of the oxygen carrying solutions may be added in the near future.

Artificial Organs↗
PubMed1992

[Surgical techniques of ventricular assist device].

Since October 1982 to April 1990, we had 16 ventricular assist device (VAD) cases in our institute. Using this VAD system that was produced by Nippon Zeon company, surgical techniques for cannulation and de-cannulation could be made very easily, and connection between cannulae and pump also could be performed quickly. In this article, the actual surgical techniques and the know-how were illustrated in detail. If this techniques can be more accustomed, the clinical results of VAD cases will be improved.

Cardiac Catheterization↗
PubMed1990

[Effectiveness and limitations of IABP or LVAD in right ventricular dysfunction].

IABP and well functioning left ventricular assist device for a failing left ventricle have potential for altering the loading condition of the right heart. Depending on the extent of myocardial damage and the pulmonary vascular resistance, IABP and LVAD can have different degree of hemodynamic effect on the right ventricle. We examined 20 clinical cases who required IABP support to wean from cardiopulmonary bypass. In 10 cases (group I), CVP rose up above 20 cmH2O within 12 hrs of post operative period. In another 10 cases (group II), CVP rose less than 20 cm H2O. Then we compared hemodynamic change (m-PAP, PVR, CVP, PAWP, CI and RVSWI) between two groups until 72 hrs of post operative period. No significant differences were noted in PVR and CI between two groups, but CVP, m-PAP, PAWP and RVSWI were markedly higher in I group. Reduction of RV afterload produced with an IABP may probably be due to degree of recovery of failing left ventricular function. It is though that IABP has less favorable effect on right ventricular in the cases whose CVP elevate above 20 mmH2O within 12 hrs after operation than in those with CVP below 20 cmH2O. Clinical studies were made on 4 cases with biventricular failure in our experiences of 8 LVAD cases (LV aneurysmectomy + VSP closure, MVR + AVR + CABG + LV aneurysmectomy, CABG + LV aneurysmectomy and MVR + CABG). LVAD seems to have more beneficial effect on RV afterload, than IABP right ventricular dysfunction, however, is likely to continue in the cases whose CVP elevates above 30 mmH2O even if LVAD is used.

Adult↗
PubMed1989

[Effect of different kinds of toothbrushes on toothbrushing pressure and plaque removal in the scrubbing method of toothbrushing (5). Toothbrushes with nylon bristles arranged in different lengths along the toothbrush shank and with different types of toothbrush bristle tip].

The purpose of this study (Report 5) was to investigate the effect of difference in the length of toothbrush shank and type of tip of toothbrush bristle on toothbrushing pressure and plaque removal in the scrubbing method. Four kinds of toothbrushes which were different in length of shank (30 mm, 40 mm) and type of bristle tip (round type, tapered type respectively) were used in this study. Referring to the results of our previous reports (1-4), the dimension of new toothbrushes were determined as follows, nylon bristles: 40 mm long and 0.20 mm in diameter, brushing surface: 30 mm long, bristles: 3 rows with 26 tufts, and a straight handle. Twelve subjects participated in this experiment. Plaque scores were measured before and after toothbrushing. Then plaque removal rates were calculated. Toothbrushing pressure was determined using Watanabe's method. The average toothbrushing pressure of the toothbrush with a 40 mm long shank (301.6 +/- 84.1 g/cm2) was higher than that with a 30 mm long shank (294.7 +/- 74.8 g/cm2), and that with a tapered bristle type (316.7 +/- 90.4 g/cm2) was higher than that with a round type bristle (279.6 +/- 61.7 g/cm2). However statistically significant differences were not found among the four toothbrushes in brushing pressure and in plaque removal on total teeth surfaces and on distal surfaces of the most posterior teeth (P less than 0.05; two-way ANOVA).

Dental Plaque↗
PubMed1989

[The results of surgical treatment of post-infarction left ventricular aneurysms].

The surgical results of post-infarction left ventricular aneurysmectomy have been evaluated in 24 patients approximately 1 year after operation. In 20 patients coronary artery bypass grafting (CABG) was also carried out. In 8 patients mechanical circulatory assist such as intra-aortic balloon pump (IABP) or left ventricular assist device (LVAD) was undertaken for the purpose of weaning from cardiopulmonary bypass. Postoperative left ventricular function, such as ejection fraction and cardiac index, and classification of the New York Heart Association were improved significantly after aneurysmectomy. However, postoperative improvement of these parameters was not remarkable in cases of poor preoperative left ventricular function. Preoperative left ventricular function revealed to be poor in multiple vessel disease, and concomitant coronary artery bypass grafting with aneurysmectomy can be performed with good long-term results and significant improvements of postoperative cardiac function. In patients that had showed the end-diastolic perimeter more than 40% and the shortening rate of transverse axis at the left ventricular base less than 20%, postoperative improvement of cardiac function revealed unsatisfactory. Mechanical circulatory assist showed lifesaving effect, but in cases that required IABP or LVAD postoperative cardiac function has not improved significantly.

Adult↗
PubMed1989

[Multiple organ failure following open heart surgery in adults].

The cases multiple organ failure (MOF) which occurred post-operatively following open heart surgery in adults were studied on a pre and post-operative hemodynamics. Post-operative low cardiac output syndrome (LOS) was thought to result in decreased renal and hepatic perfusion with subsequent ischemic damage to these organs. Therefore, to management MOF, we have to prevent post-operative LOS, for example, administration of cathecholamine and vasodilator, and early clinical application of IABP and ventricular assist device (VAD). In a post-operative hemodynamics, the cases of severe right ventricular failure tend to have more protracted MOF. It was though that MOF could be minimized with shortened cardiopulmonary bypass duration, and early application of assisted circulation.

Adult↗