Pulse generating device

Abstract

A pulse generator has a rigid body with a resilient flow conduit passing therethrough. Pressure is periodically selectively applied to the interior of the body which compresses the flow conduit and induces a pressure pulse in the fluid contained therein. The pulse generator may be used as a stand alone pump or in concert with a continuous flow pump to provide a pulsatile output flow having customized waveform characteristics. The pulse generator may be used with medical equipment such as a heart-lung bypass machine or a dialysis machine.

1 . A pulse generator for fluid flow, comprising:
 (a) a substantially rigid body defining a pressure cavity;   (b) a resilient flow conduit extending through the pressure cavity and arranged to carry a first fluid therein; and   (c) a pressure inlet communicating with the pressure cavity for introducing a second fluid into the pressure cavity, such that the first fluid may be exposed to a time-varying pressure signal introduced through the pressure inlet without mixing of the first and second fluids.   
   
   
       2 . The pulse generator of  claim 1  in which the flow conduit is generally S-shaped. 
   
   
       3 . The pulse generator of  claim 1  in which the flow conduit has a four-sided cross-sectional shape defined by spaced-apart walls extending between radiused corners. 
   
   
       4 . The pulse generator of  claim 1  in which the flow conduit has a cross-sectional shape including a pair of spaced-apart lobes connected by a pinched waist. 
   
   
       5 . The pulse generator of  claim 1  in which the flow conduit has a cross-sectional shape including a pair of spaced-apart lobes connected by a pinched waist. 
   
   
       6 . The pulse generator of  claim 1  in which the flow conduit has a cross-sectional shape including a plurality of spaced-apart, radially-extending lobes. 
   
   
       7 . The pulse generator of  claim 1  in which the flow conduit has a cross-sectional shape including:
 (a) a double-walled, generally C-shaped portion; and a plurality of spaced-apart, a flexible bridge connecting free ends of the C-shaped portion;   (b) wherein the C-shaped portion and the flexible bridge cooperate to define a central opening.   
   
   
       8 . The pulse generator of  claim 1  wherein the pressure cavity is shaped such that a pressure signal applied thereto will propagate symmetrically therein. 
   
   
       9 . A pulse generator for fluid flow, comprising:
 (a) a substantially rigid housing which defines an open cavity, the housing including an inlet and outlet communicating with the cavity;   (b) a flexible diaphragm which closes off the cavity; and   (c) an actuator operably connected to the diaphragm and adapted to selectively move the diaphragm from a first position in which the pulse generator encloses a first fluid volume, and a second position in which the pulse generator encloses a second fluid volume less than the first fluid volume.   
   
   
       10 . The pulse generator of  claim 9  in which the diaphragm forms a portion of a torus. 
   
   
       11 . The pulse generator of  claim 9  further including a programmable controller operably connected to the actuator. 
   
   
       12 . A fluid circulation system, comprising:
 (a) a circulation pump for a first fluid;   (b) a first pulse generator disposed in series flow with the circulation pump, the first pulse generator including:
 (i) a substantially rigid first body defining a first pressure cavity; 
 (ii) a resilient first flow conduit extending through the first pressure cavity and arranged to carry the first fluid therein; and 
 (iii) a first pressure inlet communicating with the first pressure cavity for receiving a second fluid into the first pressure cavity, such that the first fluid may be exposed to a pressure signal received through the first pressure inlet without mixing of the first and second fluids; and 
   (c) a control mechanism operably connected to the first pressure inlet and adapted to introduce a pressure signal into the first pressure cavity so as to impress a predetermined time-varying pressure profile into the first fluid through the first flow conduit.   
   
   
       13 . The fluid circulation system of  claim 12  in which the circulation pump is a type generating a substantially constant output pressure in the first fluid. 
   
   
       14 . The fluid circulation system of  claim 12  in which the control mechanism includes:
 (a) a source of pressurized fluid; and   (b) a valve operable to selectively transfer the pressurized fluid to the first pressure inlet.   
   
   
       15 . The fluid circulation system of  claim 12  in which the first pulse generator has a displacement capacity, and in which the control mechanism is adapted to control the circulation pump and the first pulse generator such that the first pulse generator operates in a preselected displacement range within the displacement capacity. 
   
   
       16 . The fluid circulation system of  claim 12  further including:
 (a) a second pulse generator disposed in series flow with the circulation pump and the first pulse generator, the second pulse generator including:
 (i) a substantially rigid second body defining a second pressure cavity; 
 (iii) a resilient second flow conduit extending through the second pressure cavity and arranged to carry the first fluid therein; and 
   (b) a second pressure inlet communicating with the second pressure cavity for receiving a second fluid into the second pressure cavity, such that the first fluid may be exposed to a pressure signal received through the second pressure inlet without mixing of the first and second fluids;   wherein the control mechanism is operable to selectively pressurize the second pulse generator to a degree so as to substantially close off flow through the second flow conduit.   
   
   
       17 . The fluid circulation system of  claim 12  further comprising equipment for treatment of a bodily fluid connected in series flow therewith. 
   
   
       18 . A fluid circulation system, comprising:
 (a) a first pulse generator including:
 (i) a substantially rigid first body defining a first pressure cavity; 
 (ii) a resilient first flow conduit extending through the first pressure cavity and arranged to carry the first fluid therein; and 
 (iii) a first pressure inlet communicating with the first pressure cavity for receiving a second fluid into the first pressure cavity, such that the first fluid may be exposed to a pressure signal received through the first pressure inlet without mixing of the first and second fluids; and 
   (b) a second pulse generator connected in series flow with the first pulse generator, and including:
 (i) a substantially rigid second body defining a second pressure cavity; 
 (ii) a resilient second flow conduit extending through the second pressure cavity and arranged to carry the first fluid therein; and 
 (iii) a second pressure inlet communicating with the second pressure cavity for receiving a second fluid into the second pressure cavity, such that the first fluid may be exposed to a pressure signal received through the second pressure inlet without mixing of the first and second fluids; and 
   (c) a control mechanism operably connected to the first and second pressure inlets and adapted to:
 (i) cyclically pressurize one of the first pulse generator so as to impress a predetermined time-varying pressure profile into the first fluid; and 
 (ii) cyclically pressurize the second pulse generator to a degree so as to substantially close off flow through the second flow conduit in coordination with the pressurization of the first pulse generator, such that the first fluid is moved through the fluid circulation system in a single direction. 
   
   
   
       19 . The fluid circulation system of  claim 18  further comprising:
 (a) a third pulse generator connected in series flow with the first and second pulse generators, and including:
 (i) a substantially rigid third body defining a third pressure cavity; 
 (ii) a resilient third flow conduit extending through the third pressure cavity and arranged to carry the first fluid therein; and 
 (iii) a third pressure inlet communicating with the third pressure cavity for receiving a second fluid into the third pressure cavity, such that the first fluid may be exposed to a pressure signal received through the third pressure inlet without mixing of the first and second fluids; and 
   (b) a control mechanism operably connected to the third pressure inlet and adapted to selectively pressurize the third pulse generator to a degree so as to substantially close off flow through the third flow conduit.   
   
   
       20 . The fluid circulation system of  claim 18  further comprising equipment for treatment of a bodily fluid connected in series flow therewith. 
   
   
       21 . A method of generating a fluid pulse, comprising:
 (a) passing a first fluid through a resilient first flow conduit arranged to carry the first fluid therein; and   (b) while the first fluid is in the first flow conduit, introducing a pressurized second fluid into a first pressure cavity defined by a substantially rigid first body surrounding the first flow conduit, as to impress a predetermined time-varying pressure profile into the first fluid through the first flow conduit.   
   
   
       22 . The method of  claim 21 , further comprising:
 passing the first fluid through a circulation pump connected in series flow relationship with the first flow conduit so as to impress a substantially constant pressure component in the first fluid.   
   
   
       23 . The method of  claim 21 , further comprising:
 (a) passing the first fluid through a resilient second flow conduit arranged to carry the first fluid therein;   (b) introducing a pressurized second fluid into a second pressure cavity defined by a substantially rigid second body surrounding the second flow conduit;
 wherein the second flow conduit is cyclically compressed to a degree so as to substantially close off flow through the second flow conduit in coordination with the pressurization of the fluid in the first flow conduit, such that the first fluid is moved through the first and second flow conduits in a single direction. 
   
   
   
       24 . The method of  claim 21 , wherein the first fluid is a bodily fluid, further comprising passing the first fluid through equipment for treatment thereof. 
   
   
       25 . The method of  claim 21 , further comprising heating or cooling the first fluid as it passes through the first flow conduit. 
   
   
       26 . The method of  claim 21 , wherein the second fluid is at a lower pressure than the first fluid during at least a portion of the pressure profile.