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Biomedical subjects

K Mabuchi

Publications and source records attributed to K Mabuchi.

187 records · Page 11Linked to original sources
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An artificial heart driven by liquid gas.

An artificial heart (AH) driving system, in which a sac or diaphragm type blood pump is liquid gas driven, is designed. The working mechanism of this system is as follows: 1) liquid gas is used for the driving source; 2) a liquid gas is stored in its liquid state in the circuit; 3) a liquid gas is vaporized, and the vaporizing pressure squeezes the blood pump, causing ejection of blood; 4) vaporized gas is aspirated and compressed by a small compressor to liquefaction through the heat exchanger, then negative pressure is applied to the blood pump and blood is aspirated; and 5) the blood pump is driven in this closed cycle. To demonstrate the mechanism of this system, a prototype was developed using Freon 114 as the liquid gas. In this system, the maximum flow of the AH at a 100 pulse per minute rate, was about 6.9 L/min, using a 90 ml sac type blood pump. The advantages of this AH driving mechanism are as follows: 1) a small system is available because pressure chambers are not necessary; 2) a biventricular system is available, with a single compressor; 3) no compliance chamber is necessary if the system is small enough to be implanted.

Ammonia↗
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Long-term preservation of a beating heart in an artificial environment.

The natural heart could be preserved in the beating state, with appropriate afterload, for more than 24 hrs if supported by blood compatible artificial organs and biomedical engineering techniques. An artificial environment was developed using this philosophy. The system was constructed from four subsystems: circulatory, respiratory, metabolic, and environmental. In the circulatory subsystem, diastolic pressure was held at 70 to 100 mmHg by computer aided peripheral resistance, and a left ventricular assist device (LVAD) could be added when cardiac function was weakened. The respiratory subsystem was composed of an artificial lung and computer aided gas mixer for O2, CO2, and air, which kept blood PO2 and PCO2 within physiologic levels. In the metabolic subsystem, glucose and insulin were injected by infusion pump so as to maintain blood sugar within 100 to 200 mg/dl, whereas the environmental system preserved the isolated heart at 37 degrees C in a sterile water bath. Goats' hearts were connected to this system, and continued to beat for a maximum of 24 hours.

Animals↗
PubMedDate not supplied

Predictive control by physical activity rate of a total artificial heart during exercise.

No control method has yet been established for the total artificial heart (TAH) during exercise. As the simple intrinsic control method does not significantly increase cardiac output (CO), this study attempted to develop a new TAH control method that increases the CO during exercise in a manner similar to a natural heart (NH) by predicting changes in CO as a time function (TF) at various treadmill speeds. The control method for TAH was as follows: 1) an arbitrary grade of treadmill exercise was loaded onto the TAH goat; 2) a TF at this grade of treadmill exercise was determined from the physical activity rate (PAR) measurement, defined as the time average of the increase in vertical acceleration of the body; 3) operating parameters of both pumps were controlled in accordance with the TF using the computer algorithm. With the predictive control method changes in CO in the TAH were almost the same as in the NH, whereas no increase in CO occurred with the fixed control method (FC), in which operating parameters remained unchanged during exercise. Changes in blood lactate and catecholamines tended to be less than with the FC.

Animals↗
PubMedDate not supplied

A newly designed jellyfish valve for an artificial heart blood pump.

Bjork-Shiley and Hall valves used in most artificial heart blood pumps have often induced problems, which include 1) An expensive valve must be used even when the AH is used for only a few days, 2) Ring thrombus was often formed at the interface between the valve ring and blood pump, seamless fabrication was not possible, and 3) Mechanical failure often occurred. To improve these circumstances, a new jellyfish valve was designed and manufactured. The valve has a simple structure: The center of a thin circular polyurethane membrane is fixed on a polyurethane base plate, which has many holes or slits to reduce flow resistance and help hold the membrane during the diastolic phase. In a mock circulation study, the valve displayed performance similar to the Bjork-Shiley valve. A small amount of regurgitant flow was observed at valve closure, in comparison with the Bjork-Shiley valve. It was recognized in the flow visualization study that the central region of the membrane was washed out well by the flapping of the membrane. This jellyfish valve is promising for use in a AH blood pump.

Equipment Design↗
PubMedDate not supplied

Can total artificial heart animals control their TAH by themselves? One year survival of a TAH goat using a new automatic control method (1/R control).

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.

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