US3758237A - Device for producing a pulsating flow of a fluid - Google Patents

Abstract

Device for producing a pulsating flow of a fluid. The device comprises a vessel receiving the fluid and an inflatable bag within the vessel. The interior of the bag is connected to means for producing a pulsating gas flow including a gas valve controlled electrically by a pulse generator, the frequency and ratio between the work time and rest time of the generator being variable. The resulting pulsating fluid issues from the vessel by way of an outlet.

Description

Elite States Patent 1 Kachelhoifer Sept. 11, 1973 BEVHCE FOR PRODUCING A PULSATING FLOW OF A FLUID [75] inventor: Jean Kachelhotter,

Strasbourg-Cronenbourg, France [73] Assignee: Institut National De La Sante Et De La Recherche Medicale, Paris, France 22 Filed: Jan. 18,1972

I21] Appl. No.: 218,719

[30] Foreign Application Priority Data 417/384, 385, 557; 3/DIG. 2; 128/DIG. 3, 1 D; 91/459, 460, 280; 137/13 {56] References Cited 2,971,465 2/1961 Caillaud 417/383 X 3,123,007 3/1964 Orr .L 417/383 2,033,210 3/1936 Tennant et al.... 417/383 3,658,443 4/1972 Fumagalli 1 417/384 3,507,583 4/1970 James 417/385 X FOREIGN PATENTS OR APPLICATIONS 221,685 11/1957 Australia 417/383 241,321 8/1960 Australia 417/394 989,736 4/1965 Great Britain 417/384 Primary ExaminerCarlton R. Croyle Assistant ExaminerRichard Sher Att0rneylrvin S. Thompson et al.

[57] ABSTRACT Device for producing a pulsating flow of a fluid. The device comprises a vessel receiving the fluid and an inflatable bag within the vessel. The interior of the bag is connected to means for producing a pulsating gas flow including a gas valve controlled electrically by a pulse generator, the frequency and ratio between the work time and rest time of the generator being variable.v The resulting pulsating fluid issues from the vessel by way UNITED STATES PATENTS of an outlet- 2,87l,789 2/1959 Kiffer et a1 417/383 X 5 Claims, 3 Drawing Figures 14 1 l3 3 10 ll 15 9 l f e PATENTED SEP! I i973 SHEET 1 UF 2 PATENTEB SEP] 1 I973 SHEET 2 UP 2 Fig.2B

DEVICE FOR PRODUCING A PULSATING FLOW OF A FLUID The present invention relates to a device for trans forming the continuous flow of a fluid into a pulsating flow. More particularly, in a special application, the invention relates to a device for obtaining in vitro a blood flow having physiological arterial characteristics.

At the present time, devices for perfusing organs isolated from their normal environment are employed more and more frequently in physiological or experimental surgery laboratories. In conventional perfusion devices in general use, the perfusion liquid is made to flow by a pump which is either peristaltic or has rollers and produces a continuous flow. However, some perfusion devices having a pulsating flow exist. They employ mostly an alternating displacement of a piston associated with a pair of valves. Such devices are often expensive, lack flexibility as concerns the obtainment of desired pressure waveforms, and are not atraumatic when the perfusion liquid is constituted by blood.

An object of the invention is to remedy the drawbacks of devices of the conventional method'of perfusing organs, and to provide a simple method for obtaining within a fluid in motion or at rest pulses or pressure atmosphere through a tap 13. The valve 10 is convariations which are either single, sequential or repetitive.

The invention provides a device for producing a pulsating flow of a fluid, comprising a closed vessel which communicates with a constant-flow pump connected to a source of fluid and with a load to be supplied with pulsated fluid, said vessel being adapted to contain permanently an amount of fluid, and a variable-volume pressure-modulating element located in the vessel and connected to a pulse-producing source whereby it is possible to vary the volume of said element.

Owing to these features, the device according to the invention furnishes at its outlet a composite pressure wave including a constant component and a variable modulating component which usually has a smaller amplitude than the constant component.

Preferably, the pressure modulating means is a small balloon or inflatable bag composed of elastically yieldable material and the impulsive source comprisesa reservoir of a gas under pressure connected to the bag through a valve.

Further features and advantages of the invention will be apparent from the ensuing description with reference to the accompanying drawings.

in the drawings FIG. 1 is a simplified diagram of a device for producinga pulsating flow of liquid according to the invention, and

FIGS. 2A and 2B are diagrams comparing the pressures produced in the femoral artery of a dog and in the arterial branch of .a dog intestine segment undergoing extra corporal perfusion through the agency of a device according to the invention (pressure expressed in millimetres of mercury with respect to time).

In the embodiment shown in FIG. I, the device for producing a pulsating flow of a fluid comprises a constant-flow pump 1, for example of the type having rollers. This pump draws in, for example, perfusion liquid through a pipe 2 and discharges it continuously through a pipe 3 connnected to a closed vessel 4 which is preferably cylindrical. The vessel 4 is connected in its lower part to an outlet pipe 5 through which the pulsating liquid flows to an organ which must be irrigated. The vessel 4 can be connected to the atmosphere through a tap 6 which is normally closed and is provided to permit filling the vessel 4.

An element having a variable volume or modulator 7 is immersed in the liquid contained in the vessel 4. It is preferably in the form of a small balloon or inflatable bag of elastically yiedable material (for example rubber or elastic plastics material) which is secured to a pipe 8 which is fixed with respect to the vessel 4.

A reservoir 9 of gas under pressure, such as nitrogen or air, is connected to an electrically-operated valve 10 having three ways through a pressure-reducing valve and pressure gauge 1 1. An appropriate three way valve is of the type sold by H.F.T., Paris, France, under n 5V-3-D. 90,032 under licence of Skinner Electric Valve Division, U.S.A. The valve 10 is connected to the pipe 8 through a tap 12 and to a pipe 14 leading to the trolled by an electric pulse generator 15, its pulse frequency being adjustable, for example, between 3 and 300 per minute and its mark-to-space ratio being settable as desired. Such generators are well known in the art and commerciallyiavailable so that no description need be made thereof here. For this purpose, the pulse generator n lV-lOOC-Electrona, manufactured and sold by Electrona, l3,rue J. Jaures 67380- Lingolsheim, France, is particularly appropriate.

- The device according to the invention operates in the following manner The vessel 4 is filled either partly or completely by operating the pump 1 and opening the tap 6 leading to the atmosphere, the pipe 5 being temporarily closed by a tap (not shown).

The gas circuit upstream of the valve 10 is put under gaseous pressure whose value is chosen, bearing in mind the geometric and mechanical characteristics of the vessel 4 and of the modulator 7, as a function of the amplitude of the pulsations it is desired to obtain.

The pulse frequency and the ratio between the work time (for example systolic time) and rest time (for example diastolic time) are set in the pulse generator 15 controlling the electrically operated valve 10 and can be modified and adjusted at any time. In the absence" of the taps l2 and 13 regulating the gaseous flows, the waveform of the pressures then obtained in the outlet pipe 5 is that of two damped oscillating movements which follow each other. The first is positive with'respect to the mean pressure and correspondsto the pressurizing of the modulator 7 (opening of the valve'l0), whereas the second, which is negative,occurs when the valve 10 is closed, which brings about simultaneously (it being a'three-way valve) the opening of the dis-* charge circuit of the pressurizing gas. and therefore a sudden depressurization of the modulator '7.

Such a waveform is, usually of no interest and in particular not physiological, but its configuration or shape can be corrected by a regulation of the gaseous supply and discharge flows .to which the modulator 7 is sub.- jected. Thus the partial and controlled closureof the tap 12 stops the sudden-rise in pressure, avoids the appearance of an oscillatory operation and permits suitably shaping the rising part (for example anacrotic) of the waveform. similarly, the shape of the descending,

part (for example dicrotic) which starts at the start of the depressurization is adjusted by regulating the discharge flow (tap 13), that is, the deflation of the modulator 7. The combination of these two possibilities of adjustment enables a wide range of pressure profiles, and in particular physiological profiles, to be obtained. Measurements and recordings of pressures have been carried out in the arterial branch of segments 30 centimetres long of the intestine of the dog undergoing extra-corporal perfusion. The pressure obtained at 1 cm from the mesentery is practically identical in amplitude, frequency and profile to that measured in a femoral artery (see respectively FlGS. 2A and 2B).

The device according to the invention has in its very principle of operation an interesting property the mean pressure and the differential pressure are independent. Indeed, for given mechanical characteristics of materials constituting the vessel 4 and the modulator 7, the amplitude of the pulsations (pressure differential) is only a function of the gaseous pressure supplied to the modulator. The mean pressure is dependent only on the resistance to flow of the downstream part of the circuit and the continuous flow applied by the roller pump 1. Consequently, it is possible to obtain, within a wide range of flows, a pulsatile operation having varied characteristics, and in particular physiological characteristics, irrespective of the chosen mean pressure of flow.

With the device according to the invention it is possible a. To obtain flows having physiological pressure profiles. ln this field of application it has high flexibility, related to the possibilities of regulation of the gaseous pressurization and depressurization flows. It is simple and can be easily adapted to any conventional apparatus for perfusion of isolated organs and even extracorporal circulation assemblies employed in cardiovascular surgery. In such apparatuses, the conversion of the continuous flow into a pulsatory flow can be effected for example in the region of the bubble remover which usually directly precedes the arterial branch of the perfusion circuit.

b. To obtain remote controls or relays. The device according to the invention is of utility wherever a fluid (liquid or gas), which is at rest or flows, constitutes the support or vehicle for the transmission of an information convertible into pulses or pressure variations.

Having now described my invention what [claim as new and desire to secure by Letters Patent is l. A device for irrigating an element such as a biological organ with a pulsating flow of a liquid comprising a closed vessel having an inlet, a constant-flow pump connected to said inlet and to a source of said liquid for supplying the latter into said closed vessel and for maintaining therein a substantially constant liquid level, said closed vessel further comprising an outlet connected to said element, a variable-volume pressuremodulating element immersed in said liquid contained in the vessel, and means connected to said pressuremodulating element for controlling the variations of the volume of the latter.

2. A device for irrigating an element such as a biological organ with a pulsating flow of a liquid comprising a closed vessel having an inlet, a constant-flow pump connected to said inlet and to a source of said liquid for supplying the latter into said closed vessel and for maintaining therein a substantially constant liquid level, said closed vessel further comprising an outlet connected to said element, a bag of an elastically yieldable material in the liquid contained in the vessel, a reservoir containing a fluid under pressure, pipe means putting the outlet of the reservoir in communication with the interior of the bag and pulsatory valve means inserted in said pipe means for producing a pulsating flow of the fluid from the reservoir.

3. Adevice as claimed in claim 2, wherein the valve means is an electrically operable valve means and said device further comprises a generator of electric pulses connected to the valve means to control operation of the valve means, the mark-to-space ratio of the generator being variable.

4. A device as claimed in claim 2, wherein the valve means is a three way valve capable of defining alternatively two fluid paths, one of said paths being connected in said pipe means between said bag and said reservoir and the other paths being connected between said pipe means and atmosphere, said device further comprising a first regulating valve connected in said pipe means between said bag and said three way valve and a second regulating valve connected between said three way valve and atmosphere. v

5. A device as claimed in claim 2, further comprising a tap for putting the inside of the vessel in communication with the atmosphere when the vessel is being filled with fluid.

Claims (5)

1. A device for irrigating an element such as a biological organ with a pulsating flow of a liquid comprising a closed vessel having an inlet, a constant-flow pump connected to said inlet and to a source of said liquid for supplying the latter into said closed vessel and for maintaining therein a substantially constant liquid level, said closed vessel further comprising an outlet connected to said element, a variable-volume pressuremodulating element immersed in said liquid contained in the vessel, and means connected to said pressuremodulating element for controlling the variations of the volume of the latter.

2. A device for irrigating an element such as a biological organ with a pulsating flow of a liquid comprising a closed vessel having an inlet, a constant-flow pump connected to said inlet and to a source of said liquid for supplying the latter into said closed vessel and for maintaining therein a substantially constant liquid level, said closed vessel further comprising an outlet connected to said element, a bag of an elastically yieldable material in the liquid contained in the vessel, a reservoir containing a fluid under pressure, pipe means putting the outlet of the reservoir in communication with the interior of the bag and pulsatory valve means inserted in said pipe means for producing a pulsating flow of the fluid from the reservoir.

3. A device as claimed in claim 2, wherein the valve means iS an electrically operable valve means and said device further comprises a generator of electric pulses connected to the valve means to control operation of the valve means, the mark-to-space ratio of the generator being variable.

4. A device as claimed in claim 2, wherein the valve means is a three way valve capable of defining alternatively two fluid paths, one of said paths being connected in said pipe means between said bag and said reservoir and the other paths being connected between said pipe means and atmosphere, said device further comprising a first regulating valve connected in said pipe means between said bag and said three way valve and a second regulating valve connected between said three way valve and atmosphere.

5. A device as claimed in claim 2, further comprising a tap for putting the inside of the vessel in communication with the atmosphere when the vessel is being filled with fluid.

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