Abstract:
In a small sized pump driving unit, a fluid pump is used for driving the pump for supporting of substituting of cardiac function. The fluid pump can generate pressure fluctuations that can generate pulsation of the pump for supporting or substituting of cardiac function and produces sufficient performance to drive the pump unit.

Description:
This application is a continuation of application Ser. No. 09/843,858 filed on Apr. 30, 2001, now abandoned. The entire disclosure of Japanese Patent Applications No. 2000-129596 filed on Apr. 28, 2000 and No. 2001-074968 filed on Mar. 15, 2001, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to a pump driving unit for driving a pump used for supporting or substituting of cardiac function, such as a blood pump which is applied to an artificial heart or an intra-aortic balloon pump which supports cardiac function. More particularly, this invention provides for miniaturization of the pump driving unit. 
   2. Description of the Background 
   A known type of a pump driving unit for driving a pump used for supporting or substitution of cardiac function, such as a blood pump or IABP (Intra-Aortic Balloon Pump) is disclosed in Japanese Patent Laid-Open Publication No.11-188091. This publication discloses an air pressure driven type pump driving unit, which drives a pump used for an artificial heart. 
   A conventional air pressure driven type pump driving unit such as the above cited publication, generally has a compressor, a high pressure accumulation chamber and a low pressure accumulation chamber, and is placed outside of a human body. The high pressure accumulation chamber is connected to an output port of the compressor and the low pressure accumulation chamber is connected to an intake port of the compressor, respectively. These two accumulation chambers are connected to a connection port of the artificial heart through a selector valve. In response to operation of the selector valve, these accumulation chambers are selectably communicated with the connection port, and pressure fluctuation thereby occurs. The pressure fluctuation which is generated between these pressure accumulation chambers drives a pump used for supporting or substitution of cardiac function. 
   The conventional air pressure driven type pump driving unit must have a compressor, and high and low pressure accumulation chambers, and so is bulky. To reduce the size of the driving unit, U.S. Pat. No. 5,766,207 suggests placing the compressor in the low pressure accumulation chamber. However, the unit still requires a compressor and a low pressure accumulation chamber, which limits the size reduction of the pump driving unit. Since the pump driving unit must always accompany the user, this limits the user&#39;s range of activity. 
   SUMMARY OF THE INVENTION 
   In view of above mentioned disadvantage of the conventional driving unit, it is an object of the present invention to produce a pump driving unit that has minimized unit size. 
   To achieve the above and other objects, a pump driving unit for driving a pump used for supporting or substitution of a cardiac function comprises a fluid pump which is a driving source of the pump used for supporting or substitution of a cardiac function. 
   Further, the pump driving unit for driving a pump used for supporting or substituting of cardiac function comprises an isolator forming therein a first space, and a second space divided from the first space by a flexible member and connected to the pump, a fluid pump connected to the first space and operated so as to supply a fluid media therein to the first space or to suck a fluid media into the first space, and a control unit for controlling an operation of the fluid pump. 
   The fluid pump generates sufficient pressure fluctuations to generate pulsative operation of the pump used for supporting or substitution of cardiac function such as the blood pump or the balloon pump, and need not use an accumulation chamber to adjust the pressure. Therefore, the pump driving unit can have a small size. Further, the fluid pump is smaller than a compressor so that the size of the pump driving unit can be minimized. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawing figures in which like elements are designed by like reference numerals and wherein: 
       FIG. 1  illustrates a structure of the first embodiment of a pump driving unit according to the invention; and 
       FIG. 2  illustrates a structure of the second embodiment of a pump driving unit according to the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   This invention will be described in according to preferred embodiments which are shown in attached drawings. 
   First Embodiment 
     FIG. 1  shows a schematic structure of the first embodiment of the invention. A pump driving unit  1  has an isolator  11 , a fluid pump  12 , a control unit  13  and a reservoir tank  14 . The aforementioned elements are retained in a housing  100  of a pump driving unit  1 . 
   The interior of the isolator  11  is divided into a first space  112  and a second space  113  by a flexible member such as a diaphragm  111 . In this embodiment, the diaphragm  111  is made from fluorine rubber material. 
   The fluid pump  12  pulsatively drives a blood pump  51 . In other words, the fluid pump  12  is used as a driving source of the blood pump  51 . A turbine type fluid pump  12  is used in this embodiment. An impeller turbine  122  is disposed in a pump housing  121 . The fluid pump  12  rotates in both clockwise and counterclockwise directions. The pump housing has a first port  121   a  and a second port  121   b . The first port  121   a  communicates with the first space  112  of the isolator  11  through a fluid path  21 . The second port  121   b  communicates with the reservoir tank  14  through a fluid path  22 . The impeller turbine  122  is driven by a motor  123 . The motor  123  drives the impeller turbine  122  bidirectionally, that is, in either a clockwise direction (shown by arrow B in  FIG. 1 ) or a counterclockwise direction (shown by arrow A in  FIG. 1 ). The rotational speed of the motor  123  is variably controlled through the control unit  13 . A brushless motor or a stepping motor can be used as the motor  123  in this embodiment. 
   A first pressure sensor  31  is arranged at the first space  112  and a second pressure sensor  32  is arranged at the second space  113  to detect actual pressure levels in these spaces. The detected actual pressure levels in the isolator are transmitted to the control unit  13 . 
   The second space  113  communicates with the blood pump  51  through a fluid path  23 . An intake and exhaust control valve  41  is mounted in the path  23  to control a pressure level in the path  23 . A two way (open-close) valve is used in this embodiment, and the valve  41  is controlled by the control unit to retain the pressure level in the path  23  within a predetermined range. 
   The control unit  13  controls the operation of the fluid pump  12  through the motor  123  and the operation of the intake and exhaust control valve  41 . In order to coordinate appropriate user conditions, the control unit  13  controls motor  123  and the intake and exhaust control valve  41  by using signals from first and second space pressure sensor  31  and  32 . The motor  123  is controlled in its direction and speed, and the intake and exhaust control valve  41  is controlled in its open-close ratio. 
   The blood pump  51  has a housing  511  and a diaphragm  512 . The inner space of the blood pump  51  is divided into a fluid chamber  513  and a blood chamber  514  by a diaphragm  512 . The second space  113  of the isolator  11  is communicated with the fluid chamber  513  of the blood pump  51 . 
   A liquid such as silicon oil is liquid tightly held in the first space  112 , the path  21 , the fluid pump  12  , the path  22  and the reservoir tank  14 . A gas such as air is gas tightly held in the second space  113 , the path  23  and the fluid chamber  513  of the blood pump  51 . Therefore, an upstream side (first side fluid) of the diaphragm  111  is contacted by silicon oil as a fluid media and a downstream (second side fluid) of the diaphragm  111  is contacted by air. 
   Operation of the first embodiment is described hereinafter. When the fluid pump  12  is driven in a counterclockwise (positive) direction (arrow A direction in  FIG. 1 ), silicon oil in the fluid pump  12  is sent to reservoir tank  14  through the path  22  and silicon oil in the first space  112  is sucked by the fluid pump  12  through the path  21  and the first port  121   a . In response to this operation, the pressure level in the first space  112  is decreased and the diaphragm  111  moves in the left direction (shown by arrow D) in  FIG. 1 . Consequently, the volume of the first space  112  is decreased and the volume of the second space  113  is expanded. According to the expansion of the volume of the second space  113 , the pressure level in second space  113  will be reduced. This decompression is transmitted to the fluid chamber  513  of the blood pump  51  through the path  23  so that the volume of the fluid chamber  513  is decreased and the shape of the diaphragm  512  is transformed from the illustrated concave shape to a convex shape. As a result of this transformation of the shape of the diaphragm  512 , the blood chamber  514  is pulsatively driven and blood is taken in. 
   When the fluid pump  12  is driven in a clockwise direction (negative direction) which means arrow B in  FIG. 1 , silicon oil in the reservoir tank  14  is sent to the fluid pump  12  through the path  22  and the second port  121   b , and silicon oil in the fluid pump  12  is sent to the first space  112  through the first port  112   a  and the path  21 . In response to this operation, the pressure level in the first space  112  is increased and the diaphragm  111  moves in the right direction (shown in arrow C) in  FIG. 1 . Consequently, the volume of the first space  112  is expanded and the volume of the second space  113  is decreased. According to the decreasing volume of the second space  113 , the gas in the second space  113  will be compressed. This compression is transmitted to the fluid chamber  513  of the blood pump  51  through the path  23  so that the volume of the fluid chamber  513  is increased and the diaphragm  512  is transformed from a convex shape to a concave shape. In terms of this transformation of the diaphragm  512 , the blood chamber  514  is pulsatively driven and blood is output from the fluid pump  51 . 
   Due to this counterclockwise and clockwise rotation of the fluid pump, the blood pump  51  is pulsatively driven. The rate of fluid pump operation (cycle of between counterclockwise and clockwise operation) determines the pulse of the blood pump  51 . 
   The transformation of the diaphragm  512 , which includes the pulse operation of the blood pump  51 , depends on the pressure level of the second space  113  and the fluid chamber  513 . In this embodiment, the pressure levels in the second space  113  and the fluid chamber  513  is set to be within the range from −26.6 Kpa to +39.9 Kpa (equal to −200 mmHg to +300 mmHg). Pressure adjustment within the above described range and the rising or falling of the pressure level are controlled by the rotation speed of the fluid pump  12 . The rotational speed of the fluid pump  12  is adjusted by controlling the output and/or intake amount of silicon oil. However, in the conventional pump driving unit, this pressure adjustment is performed by using a high pressure accumulation chamber and a low pressure accumulation chamber. In the present invention, the blood pressure in the blood pump  51  is appropriately adjust by controlling the rotational speed of the fluid pump  12 , which eliminates the need for high and low pressure accumulation chambers. 
   Second Embodiment 
     FIG. 2  shows a schematic structure of the second embodiment of the invention. In this second embodiment, a balloon pump driving unit  2  drives the balloon pump  61  instead of the blood pump  51 . The same features as in the first embodiment are given the same numbers. 
   The balloon pump  61  is connected to the isolator  11  through the fluid path  23 . The balloon pump  61  is installed in a patient&#39;s main artery (e.g., downstream main artery) and repeatedly shrinks and expands in response to the movement of the heart. The balloon pump  61  minimizes the burden of the heart and supports cardiac function. 
   A gas such as helium gas fills the second space  113 , the path  23  and the balloon pump  61 . Since helium gas is an inert gas, the gas is safe. Also, since it has low inertia, it enables high responsiveness for the balloon pump drive unit  2 . 
   A helium gas storage cylinder  42  (means for helium gas supply to the balloon pump) is installed in the path  23  via an intake and exhaust control valve  41 . When the amount of helium gas in the path  23  and/or the balloon pump  61  decreases, the helium gas storage cylinder  42  supplies additional helium gas. 
   As shown in  FIG. 2 , a pressure maintaining valve  43  is installed on the path  23  and is placed downstream of the intake and exhaust control valve  41 . The pressure maintaining valve  43  controls the pressure in the balloon pump  61  by, and is controlled in its opening and closing by the control unit  13 . 
   When the fluid pump  12  is driven in the counterclockwise direction (positive direction), which means arrow A in  FIG. 2 , silicon oil in the fluid pump  12  is sent to the reservoir tank  14  through the second port  121   b  and the path  22 , and silicon oil in the first space  112  is sucked by the fluid pump  12  through the path  21  and the first port  121   a . In response to this operation, the pressure level in the first space  112  is reduced and the diaphragm  111  moves in the left direction (shown by arrow D) in  FIG. 2 . Consequently, the volume of the first space  112  is decreased and the volume of the second space  113  is expanded. According to the expansion of the volume of the second space  113 , the gas in the second space  113  will be decompressed. This decompression is transmitted to the balloon pump  61  through the path  23 , and the volume of the balloon pump  61  is decreased and the balloon pump  61  shrinks. 
   When the fluid pump  12  is driven in the clockwise direction (negative direction), which means arrow B in  FIG. 2 , silicon oil in the reservoir tank  14  is sent to the fluid pump  12  through the path  22  and the second port  121   b , and silicon oil in the fluid pump  12  is sent to the first space  112  through the first port  121   a  and the path  21 . In response to this operation, the pressure level in the first space  112  is increased and the diaphragm  111  moves in the right direction (shown in arrow C) in  FIG. 2 . Consequently, the volume of the first space  112  is expanded and the volume of the second space  113  is decreased. According to the decreasing of the volume of the second space  113 , the gas in the second space  113  will be compressed. This compression is transmitted to the balloon pump  61  through the path  23  and the volume of the balloon pump  61  is increased and the balloon pump  61  expands. 
   According to the counterclockwise and clockwise rotation of the fluid pump operation, the balloon pump  61  repeatedly expands and shrinks so that the balloon pump  61  supports blood flow and minimizes the burden of the heart and supports cardiac function. 
   In this embodiment, the pressure level in the balloon pump  61  is set within the range from −13.3 Kpa to +26.6 Kpa (equal to −100 mmHg to +200 mmHg). The pressure adjustment within the above described range and the rising or falling of the pressure level are controlled by rotation speed of the fluid pump  12 . The rotational speed of the fluid pump  12  is adjusted by controlling the output and/or intake amount of silicon oil. In the conventional driving unit, this pressure adjustment is performed by using a high pressure accumulation chamber and a low pressure accumulation chamber. In the present invention, the blood pressure in the blood pump  51  is appropriately adjusted by controlling the rotational speed of the fluid pump  12 , and so the high and low pressure accumulation chambers are unnecessary. 
   In this second embodiment, the pressure maintaining valve  43 , which is controlled by the control unit  13 , controls rapid pressure increasing and rapid pressure decreasing in the balloon pump fit. 
   The rapid pressure increasing is accomplished in accordance with following operation. When the balloon pump  61  is at a low pressure condition, the pressure maintaining valve  43  is closed by the control unit  13 . The balloon pump  61  and the second space  113  of the isolator  11  are thus cut off from each other. Under this condition, the motor  123  drives the impeller turbine  122  in a clockwise direction (negative direction and shown an arrow B in  FIG. 2 ) and silicon oil in the fluid pump  12  is supplied to the first space  112  of the isolator  11  so that the gas pressure level in the second space  113  is increased. The pressure level in the balloon pump  61  remains low because the pressure maintaining valve  43  is closed. When the pressure level in the second space  113  reaches a sufficiently high pressure level, the pressure maintaining valve  43  is opened by the control unit  13 . In response to this operation, the accumulated pressure in the second space  113  is introduced into the balloon pump  61  in a burst and the pressure level in the balloon pump  61  rapidly changes from low pressure to high pressure. 
   A rapid pressure decrease is accomplished in accordance with following operation. When the balloon pump  61  is in a high pressure condition, the pressure maintaining valve  43  is closed by the control unit  13 . The balloon pump  61  and the second space  113  of the isolator  11  are thus cut off each other. Under this condition, the motor  123  drives the impeller turbine  122  in a counterclockwise direction (i.e. a positive direction shown by an arrow A in  FIG. 2 ), and the silicon oil in the second space  113  is sucked by the fluid pump  12  through the path  21  and the first port  121   a , and the pressure level in the second space will be reduced. The pressure level in the balloon pump  61  remains high because the pressure maintaining valve  43  is closed. When the pressure level in the second space  113  reaches a sufficiently low pressure level, the pressure maintaining valve  43  is opened by the control unit  13 . In response to this operation, the pressure in the balloon pump  61  is introduced into the second space  113  in a burst and then the pressure level in the balloon pump  61  rapidly changes from high pressure to low pressure. 
   According to this rapid pressure operation, the balloon pump has high responsiveness. 
   In this present invention, the fluid pump  12  generates sufficient pressure fluctuations to generate pulsative operation of the pump used for supporting or substitution of cardiac function such as the blood pump or the balloon pump, and need not use an accumulation chamber to adjust the pressure. Therefore, the size of the pump driving unit can be minimized. Further, the fluid pump is smaller than a compressor, so that the pump driving unit can be miniaturized. 
   Further, in the present invention, the driving unit for driving the pump used for supporting or substitution of cardiac function has the isolator  11  that has divided first and second spaces  112  and  113 , the fluid pump  12  that supplies silicon oil to the first space or sucks silicon oil from the first space  112 , and the control unit  13  that operates the fluid pump  12 . In response to supply and sucking operations of the fluid pump  12 , pulsative operations are generated in the pump. Therefore, it is not necessary to use an accumulation chamber, and the driving unit size can be reduced. 
   Furthermore in the present invention, since the pump driving unit has a fluid pump that can be driven in either a positive or negative direction, no control valve is required to control fluid supply and sucking from the pump driving unit. Therefore, the pump driving unit can be manufactured at a lower cost. 
   According to the first embodiment, the pump driving unit uses the blood pump  51  as the pump used for supporting or substitution of a cardiac function. According to the second embodiment, the pump driving unit uses the balloon pump  61  as the pump used for supporting or substitution of a cardiac function. The present invention therefore enables a smaller pump driving unit.