Power plants – Pressure fluid source and motor – Pulsator
Patent
1998-06-18
2000-08-08
Ryznic, John E.
Power plants
Pressure fluid source and motor
Pulsator
60592, 60407, F15B 700
Patent
active
060984058
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a driving apparatus for driving medical appliances, such as an artificial heart and an intra-aorta balloon pump (IABP), by alternately outputting a positive pressure and a negative pressure, and to a pressure-transfer isolator and a monitor used in the driving apparatus.
BACKGROUND OF THE INVENTION
IABP balloon catheters are often used in medical treatment of heart diseases. In the treatment, a balloon catheter is inserted into the artery near the heart f the patient, and the balloon is inflated and deflated in synchronization with the heart beat of the patient in order to assist or activate the heart function. Japanese Patent Application Laid-open No. 60-106464 (hereinafter "JP '464") discloses a medical-purpose driving apparatus for inflating and deflating such balloons.
The driving apparatus disclosed in JP '464 has a primary tube line and a secondary tube line, which are isolated from each other by a pressure-transfer isolator (simply called an isolator, or generally named a volume limiting device (VLD)). A change of pressure occurring in the primary tube line is transferred to the secondary tube line via the isolator without allowing gas flow between the secondary tube line and the primary tube line, and the resultant pressure change in the secondary tube line causes the balloon to inflate and deflate. The reason why the primary and secondary tube lines are separated from each other is that different kinds of fluid are used in these two lines, namely, one has a driving gas for actually driving the balloon, the other has a source gas from which a positive pressure and a negative pressure are generated. This is required to improve the inflation/deflation response of the balloon and to keep the secondary tube line sealed in order to prevent gas leakage except the leakage due to diffusion. This arrangement is capable of generating a pressure at a low cost, while reducing consumption of an expensive fluid used in the secondary tube line. The pressure-transfer isolator is located between the pressure source and the balloon in order to prevent excessive gas from flowing into the balloon when inflating and deflating the balloon.
In this IABP balloon catheter, helium gas, which has a small mass and a high response ability, is preferably used as the fluid to fill the secondary tube line. In this case, the helium gas functions as a driving shuttle gas. However, because of its small molecular weight, helium gas diffuses through the tube wall or the balloon film even if there are no pin holes in the secondary tube line. If helium gas is enclosed in the sealed secondary tube line, and if the balloon is continuously driven for 20 minutes to 30 minutes, the gas pressure inside this tube line decreases by several millimeters (mm) of mercury (Hg).
For this reason, the helium gas must be appropriately supplied to the secondary tube line during the use of the balloon catheter. If additional helium gas is not supplied, the amount of helium gas inside the secondary tube line gradually decreases and, finally, the balloon cannot be sufficiently inflated, which means that the balloon cannot aid the heart function of the patient any longer. Some gas supply systems are known, which monitor the interior pressure of the secondary tube line using a pressure sensor, and which supply gas so that the detected pressure does not drop below a predetermined value. In these systems, the solenoid valve is opened certain times in a short amount of time to supply helium gas from the high-pressure gas cylinder via the helium gas tank in which the pressure is adjusted to a secure level.
However, if the helium gas is additionally supplied without limitation, and if a pin hole is formed in the balloon by accident, then a great amount of gas may flow into the blood vessel of the patient, which may cause gas obturation and may be fatal to the patient. Accordingly, in the conventional driving apparatuses, the pressure of the helium gas is kept relatively low using a mechanical regulator, and the
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Ito Kiyotaka
Miyata Shin'ichi
Nippon Zeon Co. Ltd.
Ryznic John E.
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