IL95065A - Diaphragm pump for pumping blood - Google Patents

Description

DIAPHRAGM PUMP FOR PUMPING Victor Peter Chang DIAPHRAGM PUMP FIELD QF INVENTION This invention relates to pumps having a diaphragm which separates a fluid from a fluid to be A which is usually external of the controls the flow of driving fluid so as to generate the pumping action of the Such pumps may be used in a wide variety uid circuits including ventricular assist devices table artificial implantable or total artificial heart pumps and othe circulatory support devices as well as for arterial support and renal BACKGROUND ART The most important clinical problems with heart pumps and other circulatory support devices including those for heart disease are thrombosis and While these factors can be controlled by term application of drugs generally uncontrolled Thrombogenicity primarily arises from mechanical chemical interaction with foreign high mechanical stresses arising from unnatural patterns and transient pressures the tendency of blood to clot in regions of stationary Clinical experience with total hearts is somewhat Thus there have only been a few e o a ar c a ear an ve occurre ma n y n the United of America and Ventricular assist devices have been used many times for temporary support of diseased hearts in the United States of Japan and European The greatest hindrances to the clinical and commercial success of these devices been mechanical failure of complicated and fabrication process and high The thrombogenicity of circulatory support devices arises from several structural and functional Blood elements are damaged by contact with foreign materials through mechanical and The areas and the junction of the pump chamber are the main sites for thrombus formation by these Hemolysis is induced by sheer stresses which occur when adjacent streams have sufficiently different velocities and by high transient pressures produced by valve closure the Both these conditions occur predominantly near the ow conduits and valves of the blood Regions of f ow stasis may occur within pump chamber Overcoming these problems is one of the greatest challenges in the field of chronic circulatory Another factor which bears upon the design of a pump for circulatory support devices is the importance of reducing preferably the need for therapy for long terra circulatory There are physiological and other advantages arising from continuous pulsatile blood flow rather than pulsatile flow through a circulatory support Continuous blood flow helps eliminate stasis stagnation of the blood flow but may induce high shear Pulsatile flow produces an aortic waveform which is similar to the natural Prior art pumps which provide pulsatile flow include centrifugal pumps do not have valves and diaphragm pumps which do have Centrifugal use mechanical stirring as the driving As valves are not the resting state of the pum achieved driving the blood to create a flow rate which equalises the back flow caused by the Centrifugal pumps can be adapted to produce either steady or pulsatile sinusoidal In the it was asserted that hemolysis resulting from stirring in the case centrifugal was balanced by hemolysis caused by valves through water hammer effect and cavitation in the case of diaphragm recently developed valves such as the mechanical heart valve which dramatically reduces the water hammer effect have enabled improvements to be made with diaphragm The present invention is concerned with diaphragm pumps driven by pulsatile drivers and it is an object of the invention to provide such a pump which will provide improved blood flow lower hemolysis and lower DISCLOSURE OF THE INVENTION According to one aspect of the invention there is provided a pump comprising a a a flexible between the and the with the diaphragm and base a driving chamber and the diaphragm and the housing defining pump an inlet to the pump from the pump in the driving chamber for coupling the driving chamber to a pump driver adapted to direct to and from the driving chamber to drive the the pump chamber being of generally conical with the outlet being located at the apex of the conical pump chamber and the inlet being disposed at an angle inclined to the the base of the conical pump chamber and being generally tangential to the outer portion of the base of pump such that flow through the pump chamber is in the of a continuous spiral In the preferred form of the the pump is used for pumping blood and the blood enters the pump chamber tangentially to existing blood to continue in a circular path around the periphery the pump chamber causing least disruption to existing flow within the pump The motion results in an effective washout of the chamber junction which traditionally has been an area of Once within the pump the round axial of the pump chamber further evolves the circular movement of the The inflowing blood fills the space created by the descending When the diaphragm the circulating blood is constrained by continuity and conservation angular momentum as forms a converging The conical profile of the pump chamber results in the angular velocity increasing axially from the base The apically located outlet offers a path of minimum resistance to the exit of the blood the pump The shape and movement of the diaphragm assists in advancing the spiral flow towards the apex of the conical pump washes out all areas of the pum chamber and diaphragm and may reduce the amount of regurgitation through the valve during The resultant pattern eliminates flow separation and stagnation in the pump and between the conduits occurs in conventional pumps in which the conduits are and usually DESCRIPTION OP THE DRAWINGS In order that the invention may be more readily understood and put practical will now be made to the accompanying drawings in 1 is a perspective view of a for a circulatory support device according to one embodiment of the 2 is a plan view of the pump shown in 3 is a view taken along lines of 4 is a schematic diagram of a circulatory support device incorporating the pump of Figs to is a perspective view of a valve for the pump shown in 1 to 3 in its closed 6 is a view similar to 5 with the valve partially 7 is a view similar to 6 with the valve fully 8 is a view similar to 7 with the valve partly 9 is a schematic representation of the pump shown in 1 to 3 at the start of diastol 10 is a schematic representation similar to 9 at the midpoint of 11 is a schematic representation similar to 10 at late 12 is a schematic representation similar to 11 at full 13 is a schematic representation similar to 12 at the start of 14 is a schematic representation similar to 13 at late 15 is a graph of pump flow against systolic fraction for the pump shown in 1 to 3 16 a graph free plasma hemoglobin against pumping time the pump shown in to 3 The pump 10 shown in 1 to 3 includes a pump housing a base 12 and a driving diaphragm 13 The pump housing 11 and the diaphragm 13 pump chamber 14 and the base 12 and the diaphragm 13 a driving chamber The pump chamber 14 is of generally conical form with the base plane 16 of the cone adjacent to the base 12 and the apex 17 remote At the base of the pump housing 11 there an annular mounting flange 18 and at the top of the base 12 there is a annular mounting flange The pump housing 11 and the base 12 in this coupled together by means of bolts and nuts 20 which pass through the flanges 18 and The flanges 18 and 19 may be coupled together by a circumferential clamping The diaphragm 13 is clamped between and chemically bonded to the flanges 18 and 19 as can be seen in 1 and At the apex of the conical pump chamber 14 there is an outlet 21 which is perpendicularly disposed to the base plane Adjacent to the base of the pump housing 11 there is an 22 in this intersects the base plane 16 at an angle of to the vertical and is tangential to the outer portion of the base An inlet valve 23 located in tubular valve housing 24 and outlet valve 25 located in tubular valve housing 26 will be described below in relation to 5 to The housings 24 and are held in place on the inlet 22 and the outlet 21 respectively by means of cable ties The base 12 has a port 27 for coupling the driving chamber to an external pump driver adapted to direct to and from the driving which drives the diaphragm 13 in a pumping In this the port 27 is incorporated in the base 12 near the inle area and its longitudinal axis Intersects the base plane 16 at an angle of to vertical The external driver will be described below i relation to In the preferred form of the the pump housing 11 and the base 12 are made of transparent Carbo are into the epoxy around the inlet the outlet the transfer port 27 and the flanges 18 and 19 to augment the mechanical strength of the The diaphragm 13 in this formed of sandwich of a material Afte assembly of the possible areas of discontinuity such as the junction of the diaphragm 13 and the pump housing 11 and the junction of the valve housings 24 and 26 with the pump housing 11 are coated selectively with polysegmented polyurethane to eliminate any All blood contacting surfaces the interior surface of the pump chamber the diaphragm he interior of the valve housings 24 and 26 and the interior of inlet 22 and outlet are also coated with a It be appreciated that all connections within the blood circuit must be made with the minimum of the inlet 22 and outlet 21 must be as thin as possible at their respective junctions with the pump In this the pump chamber 14 has an inner diameter of 75 mm at the base plane 16 and the height of the pump chamber from the base plane 16 to the beginning of the outlet 21 is 35 As can be seen in the diaphragm 13 is of shape and in this the depth at its centre is 20 The distance between the top of the diaphragm 13 at the position at the beginning of the outlet 21 is The shape of the base 12 and the diaphragm 13 are 4 is a schematic diagram of a circulatory support device incorporating the 10 1 to outlet 21 of the pump 10 is connected through valve housing 2Θ to tubing 30 and in the case of right ventrical into the pulmonary artery and the inlet 22 is coupled through valve housing 24 to tubing 31 connected by a withdrawal cannula placed in the right atrium of the patient The port 27 of the base 12 is connected by conduit 33 to controller 34 which in turn is to compressed air supply line and vacuum line It is the function of the controller 34 to drive the diaphragm Line 37 provides an ECG signal from the patient 32 to a recorder Line 38 provides a measure of atrial pressure from the patient 32 to the recorder line 39 provides a measure of bypass total flo from the patient to the recorder and line 40 provides a measure of aortic pressure to the recorder Line 42 provides the ECG signal from the recorder 41 to the controller line 43 provides the atrial pressure from the recorder 41 to the controller 34 and line 44 provides a measure of total the recorder 41 to the controller As function of the failing heart is in the changes of left atrial pressure or total flow output plus bypass both the left atrial pressure and total flow can be automatically maintained within preset ranges simultaneously by changing the pumping duration in one cardiac cycle The inlet valve 23 shown 5 to 8 has a disc located within a ring The disc 45 has an annular flange 47 which locates disc between lower support strut 48 and upper support strut 49 integral with the ring The valve is shown closed in 5 where the upper face of the disc 45 rests against an inwardly directed flange 50 the As the valve opens the disc both pivots and slides to its fully opened position as shown in In the fully opened the flange 47 engages the lower support strut When returning to the closed position the disc 45 slides back into the ring and finally pivots back into the closed position as shown in Although tissue valves have not traditionally been used in assist devices because of their bulky frames and other diff it is possible that they may be used with the pump of the present Plastic valves may also prove to be 9 represents the start of diastole in the cardiac cycle when the inlet valves 23 is open and the outlet valve 25 is closed and shows the con of the diaphragm 13 at the commencement of inlet flow of blood in the direction arrow Fig 10 represents middle diastole where the blood pattern is clearing the junction of the diaphragm 13 and the pump housing 11 as well as the surface of the diaphragm 11 represents late diastole when the inlet valve 23 commences close and shows the formation of the spiral motion of the blood as the diaphragm 13 moves lower the driving chamber 22 At full diastole in the inlet 21 is closed and the spiral motion of the blood flow continues to develop as by arrow Fig 13 represents the start of systole until the outlet opened so that outflow As described the outlet located at the apex of the conical pump chamber so that during the flow is directed in a convergent helical fashion through the outlet as indicated by arrow Smaller volume of regurgitation through the inlet valve occurs due to the position of the diaphragm 14 represents late systole where blockage of the inlet by the diaphragm 13 in this low regurgitation through the inlet valve 23 and where there is good washout in traditionally stagnant areas of the pump chamber The end of systole is show in The flow pattern characteristics of the pump shown in Fig 1 to 3 were compared with those of a conventional pneumatic The conventional style pump chosen as a control had paraxial inlet and outlet portS The flow patterns were visualized using water with ambolite particles as tracers in a mock circulatory It was shown that during diastole of the pump of the there was a circular inlet that steadily involved the entire flow field in a coherent spiral The angled tangential entry of blood from the inlet port and the continuous spiral pattern resulted in a good washout of chamber During the vortex converged helically and the blood moved to pass through the apically located outlet port No areas of stagnation or turbulence could be observed visually and most of the tracer disappeared during A continuous spiral flow was observed through the whole cardiac cycle and is not interrupted by the onset of a new In the conventional on the other the ejection of tracers out of the pump each systole was less visible due to random flow patterns and areas of The excellent flow characteristics of the pump of the invention were also clearly demonstrated by Dye Washout tests in which superior washout of the pump housing and junction was Washout was incomplete in the conventional pump with areas of The pump of the invention was subjected to static The of the pump was 120ml with the diaphragm at end reducing to 45ml at end resulting in a calculated stroke volum of Pressure testing up to 100 psi yielded no leakage or breakage of the The diaphragm was tested for durability under full movement at a pulse rate of 120 under zero No damage was observed after over three months of The pump of the was also subjected to a dynamic test in a mock circulatory loop and performance curves obtained under various physiological driving Typical performance data is shown in which shows the relationships between pump output and drive pressure and systole Higher output could have been obtained if larger calibre or shorter length cannulae had been A comparative study of in vitro hemolysis between the pump of the invention and a commercially available pump was carried out using 2 identical each filled with of fresh sheep with a hematocrit of each pump operating under flow the blood was circulated continuously for 21 Samples were taken every 4 measurement of free plasma The shown in clearly show the superiority of this pump over the conventional pump in terms of Although the invention has been described in relation to a conical pump chamber of specific shape and inclined inlet of general it is to be appreciated that variations may be made and indeed may well have to be made to suit practical The preferred angle of inclination is but a range of say 20 to either side of that angle should It has been established that a zero angle as the ninety degree angle of conventional It is possible that the angle may change when the characteristics of the cone are modified for other uses such as pediatric use intra aortic balloon pumping and arterial support Various may be made in details of design and construction without departing from the scope and the b n nvnn 17 26 on 91002 354 11 insufficientOCRQuality

Claims (14)

CLAIMS for' pumping blood

1. A pum /comprising a housing/ a base, a flexible diaphragm between the housing and the base, with the diaphragm and the base defining a driving chamber and the diaphragm and the housing defining a pump chamber, an inlet to the pump chamber, an outlet from the pump chamber, a port in the driving chamber for coupling the driving chamber to a pump driver adapted to direct fluid to and from the driving chamber to drive the diaphragm, the pump chamber being of generally conical form with the outlet being located at the apex ef the conical pump chamber and the inlet being .disposed at an angle inclined to the plane of the base of the conical pump chamber and being generally tangential to the outer housing' , portion of the base of pump jchambesr- such that flow through the pump chamber is in the form of a continuous spiral vortex.

2. A pump according to claim 1 wherein the inlet is inclined at an angle of from 30° to 60° to the plane of the base of the pump chamber.

3. A pump according to clalia 1 wherein the inlet is inclined at an angle of 45° to the plane of the base of the pump chamber.

4. A pump according to claim 1 wherein the housing and the base each have peripheral flanges which are coupled together with the periphery cf the diaphragm clamped and chemically bonded therebetween. -17-

5. A pump according to claim 1 wherein the junction of the diaphragm and housing are coated with a bio-compatible material to eliminate any discontinuity at the junction.

6. A pump according to claim 4 wherein the housing and base are made from transparent epoxy and carbon fibres are embedded around the inlet and outlet, the driving chamber port and the flanges of the housing and the base.

7. A pump according to claim 1 wherein the interior surface of the inlet, outlet and pump chamber are coated with a bio-compatible material.

8. A pump according to claim 5 or claim 7 wherein the biocompatible material is polysegmented polyurethane.

9. A pump according to claim 1 wherein the diaphragm is farmed from polyvinylchloride sheet and there is a layer of bio-compatible material on each side of the sheet.

10. A pump according to claim 1 wherein the shape of the interior of the base and that of the diaphragm are complementary. / · .

11. A pump according to claim 10 wherein the interior surface of the base is hemi-spherical .

12. A pump according to claim 1 and furthe including a valve, housing connected to the inlet and a valve housing connected to the outlet.

13. A pump according to claim .12 wherein the junction of the valve housing with the inlet and the junction of the valve housing with the outlet are coated with a bio- -18- compatible material to eliminate any discontinuity at those junctions.

14. A method of pumping a fluid comprising introducing the fluid into a conical chamber closed by a diaphragm through an inlet at or adjacent the periphery of the base of the chamber at an angle inclined to the plane of the chamber base so that the fluid enters the chamber tangentially to the existing fluid flow which causes the fluid to flow in a circular path around the periphery of the chambe , operating the diaphragm in a pum ing fashion so that when the diaphragm ascends the circulatory fluid is constrained by continuity and conservation of angular momentum to form a converging helix and the conical profile of the chamber results in the angular velocity of fluid increasing axially from the base plane, and, delivering the continuous spiral vortex of fluid so formed through an outlet at the apex of the conical chamber.