Surgery – Cardiac augmentation – With condition responsive means
Reexamination Certificate
2000-06-26
2003-06-03
Bockelman, Mark (Department: 3762)
Surgery
Cardiac augmentation
With condition responsive means
Reexamination Certificate
active
06572530
ABSTRACT:
This application is a 371 of PCT/JP98/05928
TECHNICAL FIELD
The present invention relates to a blood circulation assisting device using a continuous flow blood pump for blood feeding assistance and a diagnosis device for evaluating blood circulation state in an organism using the same.
BACKGROUND ART
Pulsatile blood flow pumps for use in blood circulation assistance include positive-displacement pumps such as a diaphram type and a pusher plate type. The ejection of the positive-displacement pump is controlled so as to satisfy the needs of an organism by being driven with a complete-filling complete-ejection mode. However, the positive-displacement pumps face difficulty in the development as an artificial heart because their structure is complicated.
On the other hand, continuous flow blood pumps have been developed for the purpose of assisting blood circulation in organism. They include not only typical types such as a centrifugal pump, an axial flow pump and a mixed flow pump, but ones which drive out blood by using a rotor, a precessional moving body, a swaying moving body, oscillations or undulations. Since their structure is simple and they can be manufactured at low cost, they show greater promise than the positive-displacement pumps. However, it is said that the continuous flow blood pumps are more difficult to control than the positive-displacement pumps.
In order to perform the circulation assistance satisfying the needs of organism, a method for monitoring one or the combination of blood pressure, blood flow rate of a pump or an organism, sympathetic nerve activity and venous oxygen saturation by using a specific sensor has been invented. However, sensors that can endure a continuous use for a long period of time without a replacement have not been developed.
In order to eliminate the use of any specific sensor, the following method for controlling the drive of the continuous flow blood pump has been proposed. The method employs a mean motor current consumption and a hydraulic performance of the pump in use to estimate the pump flow rate, thereby maintaining a constant flow rate. In other words, in the continuous flow blood pump, the correlation can be obtained between a pump speed, a generated pressure head (pressure), a pump flow rate and a motor current consumption. Therefore, when the pump speed and the motor current consumption are known, the generated pressure head and flow rate of the pump can be estimated. In addition, the pump speed and the motor current consumption can be taken and used as internal data of the motor without using any specific sensor. As a result, the pump speed can be controlled with a simple structure so as to maintain the constant flow rate. (Cf., “Control of Centrifugal Blood Pump Based on the Motor Current”, Tatsuhiko Iijima, et. al., Artificial Organs Vol. 21, No. 7, 1997, Japanese Society of Artificial Organs.)
However, the controlling method in which the pump flow rate is estimated by a mean motor current consumption and a hydraulic performance of the pump in use, thereby maintaining a constant flow rate, has several problems.
Firstly, the controlling method cannot perform an appropriate blood circulation assistance in an organism. The blood flow rate needed by an organism varies very much according to the individual's condition. For example, size, state of activity and circulated blood volume of the individual have influence on the optimal blood flow rate. Specifically, the usual cardiac output of an infant having a body weight of 10 kg is approximately 1 L/min, while the cardiac output of an adult during exertion may exceed 10 L/min. Therefore, the controlling method of merely maintaining the constant pump flow rate is not suitable for the appropriate blood circulation assistance in an organism.
Secondly, since the motor current consumption is influenced by a kinematic viscosity of the liquid during feeding, when the liquid is blood, for example, its change in character causes a large error in estimating the pump flow rate. What influences the kinematic viscosity of blood are factors such as the number of red cell (or hematocrit value), serum lipids value or serum whole protein value. These values fluctuate according to the physiological state of an organism. However, there is no method developed for continuously monitoring the kinematic viscosity or component concentration of blood. Thus, it is difficult to achieve a method for controlling a blood feeding so as to obtain the desired flow rate free from the influence by the blood characteristic such as the kinematic viscosity.
It is an object of the present invention to solve the problems of the prior art mentioned above and to provide a blood circulation assisting device using a continuous flow blood pump that realizes an appropriate circulation assistance matching a blood circulation state in an organism as well as the desired flow rate without using any specific sensor for monitoring blood character.
DISCLOSURE OF INVENTION
The blood circulation assisting device according to the present invention includes a continuous flow blood pump made of a non-displacement-type pump for blood feeding assistance, a blood removing pipe having one end attachable to a blood removal site in an organism and the other end connected to an inflow portion of the continuous flow blood pump, a blood feeding pipe having one end attachable to a blood feed site in the organism and the other end connected to an outflow portion of the continuous flow blood pump. Blood is removed via the blood removing pipe and driven out via the blood feeding pipe by the continuous flow blood pump so as to attain a predetermined flow rate. The blood circulation assisting device further includes a flow rate detection means for directly or indirectly obtaining data corresponding to a blood flow rate flowing through the continuous flow blood pump, a flow rate amplitude detection means for obtaining, from an output of the flow rate detection means, data corresponding to a fluctuation amplitude of the flow rate, and a means for adjusting an output of the flow rate amplitude detection means to a predetermined value.
With the above configuration, the flow rate amplitude detection means provides an output according to the blood circulation state in an organism, so circulation assistance matching the blood circulation state in the organism can be achieved easily by the control based on the output. In order to show more clearly that the device with the above configuration can achieve the object of the present invention, clinical backgrounds regarding blood circulation assistance and more detailed effects of the device with the above configuration are explained in the following.
Pulsation of Consumption Current Waveform of Continuous Flow Blood Pump
When a continuous flow blood pump is under usual operation, it drives out a continuous flow, and its consumption current does not show pulsation. On the other hand, unless the heart of an organism is under cardiac arrest or an arrhythmic state close to the cardiac arrest, it generates a pulsatile flow. Accordingly, when the continuous flow blood pump is used for circulation assistance in an organism, a pump flow that initially is a continuous flow is influenced by a pulsation of native cardiac output, and begins to show pulsation. As a result, current waveform of the motor, which drives the pump, also shows pulsation.
We noted this specific pulsation appeared when used in an organism, and found that an appropriate circulation assistance was made possible by referring to a pulsation of consumption current value rather than to a mean value of motor current consumption.
Relationship Between Motor Speed and Consumption Current Waveform
In the following, with respect to blood circulation assistance, “total assistance” refers to the case where cardiac output of an organism is not seen, and the blood pump drives out all the blood. However, this does not necessarily mean cardiac arrest, so the heart of the organism may generate some pressure. On the other hand, “partial assistance” refers to t
Anai Hirohumi
Araki Kenji
Oshikawa Mitsuo
Bockelman Mark
JMS Co. Ltd.
Merchant & Gould P.C.
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