Blood pump

Abstract

A pump especially designed for pumping blood comprises a bladder, the interior surface area and volume of which is changeable, i.e., it stretches and expands during the filling phase, and elastically contracts to its normal relaxed size during the ejection phase. The bladder has a fluid inlet and a fluid outlet. A device, such as a vacuum pump, alternately expands and contracts the interior surface area and volume of the bladder. Most of the interior surface area of the bladder expands and contracts in each cycle. One or more check valves or other means for causing substantially one-way fluid flow through the bladder are also provided. The pump of the invention decreases the likelihood of blood clots forming in the pump, decreases the risk of damage to blood cells, improves the pumping characteristics of the device, and decreases or eliminates the chance of foreign fluids passing into the blood stream should a tear or break occur in the bladder.

1. A fluid pump comprising:
 an elastic bladder, at least a portion of the interior surface area of said bladder being changeable between a contracted state have  having a first surface area and an expanded state having a second surface area that is substantially greater than said first surface area, said bladder having a fluid inlet and a fluid outlet;  
 means for causing substantially one-way fluid flow through said bladder;  
 a housing around at least a portion of said bladder, an annular  a volume being defined in the space between said housing and said bladder, said annular  volume being occupied by a driving fluid;  
 means for changing the pressure of said driving fluid in said annular  volume to alternately expand and contract said bladder to change the interior surface area and volume of said bladder; and  
 a driving fluid flow regulating means in said annular volume  space between said bladder and said housing for expanding and contracting selected areas of said bladder adapted, in a filling phase, to expand a selected area of said bladder adjacent said inlet and thereafter  progressively expand the remaining areas of  said bladder towards said bladder outlet  substantially in the direction of fluid flow, and during an ejection phase, to initially contract said bladder adjacent said bladder inlet and thereafter  progressively contract the remaining areas of the bladder towards said bladder outlet  said bladder substantially in the direction of fluid flow.  
 
     
     
       2. A fluid pump as in  claim 1 , wherein said actuating  driving fluid is a gas and said pressure changing means comprises a vacuum pump. 
     
     
       3. A fluid pump as in  claim 1 , wherein said actuating  driving fluid is a liquid and said pressure changing means comprises a hydraulic pump. 
     
     
       4. A fluid pump as in  claim 1 , wherein said actuating   driving  fluid is a gel. 
     
     
       5. A fluid pump as in  claim 1 , wherein said means for causing substantially one-way fluid flow comprises at least one check valve. 
     
     
       6. A fluid pump as in  claim 1 , further comprising means for controlling the expansion and contraction of said bladder in addition to said driving fluid flow regulating means. 
     
     
       7. A blood pump as in  claim 6 , further comprising  wherein said means for controlling comprises at least one of an extensible strut spanning the interior of said bladder, a band on said bladder, and said bladder comprised of a plurality of different materials. 
     
     
       8. A fluid pump as in  claim 1  for use as a ventricular assist device for a heart, wherein said outlet from said bladder is configured for connection to the aorta of the heart. 
     
     
       9. A fluid pump as in  claim 1  for pumping blood and comprising two said bladders working in combination to simulate the left and right ventricles of a heart. 
     
     
       10. A fluid pump comprising, an elastic bladder, at least a portion of the interior surface area of said bladder being changeable between a contracted state having a first surface area and an expanded state having a second surface area that is substantially greater than said first surface area, said bladder having a fluid inlet and a fluid outlet;
 a housing around at least a portion of said bladder and defining a space between said housing and said bladder for receiving a bladder actuating fluid;  
 means for alternately increasing and decreasing the pressure of said actuating fluid for alternately expanding and contracting said bladder to change the interior surface area and volume of said bladder;  
 means for causing substantially one-way fluid flow through said bladder; and  
 wherein said bladder and said actuating fluid are a unitary body of semisolid material, the surface of said semisolid material functioning as said bladder interior surface.  
 
     
     
       11. A method of pumping blood in the circulatory system of a human in the need thereof comprising the steps of
 (a) providing a blood pumping system having an extensible and contractible bladder, said pumping system having an inlet and a fluid outlet;  
 (b) connecting the inlet and outlet of said pumping system to the human's circulatory system;  
 (c) expanding a majority of the interior surface area of said pumping system by at least a few percent, including expanding the volume of the bladder to draw blood into the bladder through the inlet;  
 (d) contracting a majority of the interior surface area of said blood pumping system by at least a few percent, including contracting the volume of the bladder to pump blood out of the outlet of said system; and  
 (e) rhythmically repeating steps (c) and (d).  
 
     
     
       12. A fluid pump comprising:
 a bladder, at least a portion of the interior surface area of said bladder being changeable, said bladder having a fluid inlet and a fluid outlet, said bladder having thickness variations for controlling the expansion and contraction of said bladder, said bladder have  having a thinner wall thickness at said inlet and a thicker wall thickness at said outlet;  
 means for alternately expanding and contracting said bladder to change the interior surface area and volume of said bladder; and  
 means for causing substantially one-way fluid flow through said bladder.  
 
     
     
       13. A fluid pump comprising:
 a bladder, at least a portion of the interior surface area of said bladder being changeable, said bladder having a fluid inlet and a fluid outlet;  
 means for alternately expanding and contracting said bladder to change the interior surface area and volume of said bladder;  
 means for causing substantially one-way fluid flow through said bladder; and  
 at least one extensible strut spanning the interior of said bladder for controlling its expansion and contraction.  
 
     
     
       14. A fluid pump comprising:
 a bladder, at least a portion of the interior surface area of said bladder being changeable, said bladder having a fluid inlet and a fluid outlet;  
 means for alternately expanding and contracting said bladder to change the interior surface area and volume of said bladder;  
 means for causing substantially one-way fluid flow through said bladder; and  
 one or more bands on said bladder for controlling its expansion and contraction.  
 
     
     
       15. A fluid pump comprising:
 a housing;  
 an extensible and contractible bladder in said housing, a space defined between said housing and said bladder for receiving a bladder driving fluid, said bladder having an inlet and an outlet;  
 a check valve to at least one of said bladder inlet and outlet;  
 means for altering the pressure of the driving fluid to alternately expand and contract the interior surface area and volume of said bladder to define a pumping cycle, most of said interior surface area of said bladder adapted to expand and contract with each said pumping cycle; and  
 a driving fluid pressure regulator in said space to selectively control the rate of expansion or contraction of selected areas of said bladder.  
 
     
     
       16. A fluid pump as in  claim 15  for pumping blood, wherein said bladder is  has a curved configuration representative of a natural heart with said inlet being adjacent said outlet. 
     
     
       17. A method for reducing the formation of blood clots during blood pumping, the method comprising the steps of:
 providing a blood pump having an elastic bladder having an interior and an interior surface area; and  
 changing said interior surface area by alternately elastically stretching said bladder and elastically contracting said bladder, said changing surface area operative to reduce the formation of blood clots on said interior surface area.  
 
     
     
       18. A method for reducing the formation of blood clots during blood pumping as defined by  claim 17 , wherein said elastic bladder is enclosed in a housing, a space defined between said bladder and said housing, and wherein the step of stretching and contracting said bladder includes elastically stretching said bladder by decreasing pressure in said space to below atmospheric, and contracting said bladder by increasing the pressure in said space. 
     
     
       19. A method of  for reducing the formation of blood clots during blood pumping as in  claim 17 , wherein step of changing the interior surface area of said bladder includes changing a majority of the interior surface area of said pump. 
     
     
       20. A method of  for reducing the formation of blood clots during blood pumping as in  claim 17 , wherein said stretching step is a filling phase comprising expanding a selected area of said bladder adjacent said inlet and thereafter  progressively expanding the remaining areas of  said bladder towards said bladder outlet  substantially in the direction of flow; and said contracting step is an ejection phase, comprising initially contracting said bladder adjacent said inlet and thereafter  progressively contracting the remaining areas of  said bladder towards said outlet  substantially in the direction of flow. 
     
     
       21. A method of  for reducing the formation of blood clots during blood pumping as in  claim 17 , wherein said bladder is  has a curved configuration representative of a natural heart with said inlet being adjacent said outlet, and wherein said steps of elastically expanding and contracting said bladder comprises milking the blood through said bladder in a smooth flow substantially free from areas of turbulence and areas of stagnation. 
     
     
       22. A fluid pump comprising:
 a bladder, at least a portion of the interior surface area of said bladder being changeable, said bladder having a fluid inlet and a fluid outlet;  
 means for alternately expanding and contracting the bladder to change the interior surface area and volume of said bladder between a contracted state having a first surface area and an expanded state having a second surface area that is substantially greater than said first surface area;  
 means for causing substantially one-way fluid flow through said bladder; and  
 wherein said changeable portion of said bladder is comprised of a plurality of different materials to control the rate of expansion or contraction of selected areas of said bladder.