GB2054802A - Flow control apparatus - Google Patents

Abstract

A flow control apparatus useful in liquid flow systems for blood pressure monitoring has a flow passage with an inlet (30) and outlet (34) provided in a housing (22). A control means having a conical valve seat (33) and ball member (35) for restricting flow through the seat is provided in the inlet (30) of the passage. A valve plunger (38) slidably located within the housing (22) is resiliently biased against a second valve seat (28) provided in the passage walls of the housing. The plunger (38) includes a marine bore capillary passage (54) which effectively bypasses the second valve seat (28), thus permitting a first low flow between inlet (30) and outlet (34) when valve plunger (38) is seated against second valve seat (28). When the plunger (38) is moved from its seat (28), a second higher flow is established for flushing the device. This second higher flow rate is controlled by the valve control means (33, 35) in the inlet of the passage to prevent excessively high flow rates. <IMAGE>

Description

SPECIFICATION Flow control apparatus The present invention relates to flow control apparatus for use in fluid flow catheters of the type found in blood pressure and dynamics measurement systems.

In such systems, a catheter commonly is inserted into a patient's vessel to a location where measurements are desired. The catheter is maintained full of a neutral, sterile solution, which actually flows into the patient at a very low rate of, say, 3 ml/hr. This low flow is required to keep the catheter open, or patent, throughout its length, by preventing the ingress of blood constituents at the in-dwelling end of the catheter. By monitoring changes in the liquid pressure in the catheter, a variety of useful data can be obtained regarding the blood pressure, flow, etc. at the in-dwelling end.

When such catheters are prepared for use, they must be flushed out completely of all air which could be harmful to the patient. Since the normal small flow rate would require a long time for flushing and filling operations, prior art devices have been arranged so as to provide for much higher flow rates (rapid or fast flush mode) for use during initial flush and fill of the catheter and during use to momentarily allow a higher flow rate into the patient to clear out any debris which may have collected at the in-dweiling end of the catheter.

U.S. Patent No.3,675,891, issued Juiy 12, 1972 to Gordon S. Reynolds and others, discloses one prior art catheter flushing apparatus.

According to the present invention in its broadest aspect, a flow control apparatus comprises a housing in which a flow passage having an inlet and outlet is provided. A valve plunger slidably located within the housing is resiliently biased against a seat provided in the passage walls. The plunger includes a marine bore capillary passage which effectively bypasses the valve seat, thus permitting a first, low flow between the inlet and the outlet when the valve plunger is engaged with its seat. When the plunger is moved from its seat, a second, high flow path is established for flushing the device and its associated catheter.

Preferably, flow control means are provided in the inlet of the flow passage to limit the flow rate in the rapid or fast flush mode. Prior art devices in operation under the fast flush mode have suffered the defect of possible production of air bubbles in the drip chamber of the measurement system if the operator is not careful. These bubbles can enter the patient line and not only pose a danger to the patient but also grossly degrade the dynamic performance of associated measuring systems. The bubbles can be generated by the Venturi effect of the relatively high velocity jet of liquid flowing during the rapid flush mode. By provision of a flow limiting device in the inlet of the passage, excessive flow rates are avoided and the risk of bubble generation is minimized.

In one embodiment of the invention which is described hereinafter, the downstream end of the flow passage opens into a plenum bounded on its lower end by a flexible pressure transmitting diaphragm. The plenum is oriented and configured relative to the flow passage so that air in the plenum is easily flushed out during fill prior to use.

The diaphragm enables pressure monitoring apparatus to be isolated from the patient and yet maintained in pressure communication with the patient.

In order that the invention might be clearly understood, several embodiments thereof will hereinafter be described by way of example only with reference to the accompanying drawings. Various features and advantages of the invention will be noted as the description proceeds included amongst which is provision for overpressure release to prevent damage to associated pressure instrumentation, suitability of the apparatus for simple single handed actuation, a facility that the apparatus can be emptied of solution easily, and the inexpensive construction of the apparatus rendering it economically disposable following use.

In the accompanying drawings:~ Figure 1 shows a digrammatical view of flow control apparatus of the invention in a dynamic measurement system; Figure 2 shows an elevational view, partially in section, of one embodiment of the invention; and Figure 3 shows an elevational view, partially in section, of another embodiment of the invention in which a pressure transmitting diaphragm is built into the apparatus.

The following is a detailed description of the preferred embodiments of the invention, reference being made to the drawing in which like reference numerals identify like elements of structure in the Figures.

Figure 1 show digrammatical view of a hemodynamic measurement system 10 of a pressure infusor 14, a drip chamber 16, a flow control apparatus 18 and a pressure monitor 20.

Flow control apparatus 1 8 controls the flow from the pressure infusor 14 via drip chamber 16 to the patient through the catheter 12. A monitor 20 operatively connected to the catheter is provided for recording a variety of useful data such as blood pressure, etc.

Figure 2 show an elevational view, partially in section, of one embodiment of a flow control apparatus 18 according to the invention. A generally cylindrical housing 22 is provided with first, larger interior bore or chamber 24 and a second smaller interior bore 26, the two bores being joined by a conical valve seat 28 to provide a flow passage. An inlet passage 30 enters bore 24 from below, as illustrated, and is provided with a boss having a conventional attachment fitting 32. At the entrance of inlet passage 30 into bore 24 is an inlet passage conical valve seat 33 with valve control member 35 preferably of the ball type for restricting the flow as will be further explained below. The geometry of the valve seat and corresponding valve member 35 is provided to partially restrict the flow entering bore 24 but never to seal off the flow from passage 30 to bore 24.The inlet passage additionally preferably has a retaining ring 37 to hold control valve member 35 as may be needed while clearing the apparatus of a trapped air bubble as will be further explained below. An outlet passage 34 leaves bore 26 and is provided with a boss having a conventional attachment fitting 36. Housing 22 preferably is injection molded from a material such as clear polycarbonate plastic.

A valve plunger 38 is slidably mounted in bore 24.

An actuator shaft 40 extends from the inlet end of valve plunger 38 through a hole provided in cap 42. An actuator knob or button 44 is provided on the outer end of shaft 40. A short, resilient spring cylinder 46 of material such as silicone rubber is captured between and sealed to valve plunger 38 and cap 42. Spring cylinder 46 is sized so that when the apparatus is assembled as shown, valve plunger 38 is resiliently biased toward valve seat 28. The spring constant of spring cylinder 46 is chosen so that should the pressure at the outlet end of the apparatus approach an undesirably high level for the pressure transducer operatively connected thereto the valve plunger 38 will move to the right, as illustrated to help equalize the pressure.Plunger 38 further includes a radially extending circumferential flange 48, which is sufficiently smaller in diameter than bore 24 to allow the desired liquid flow through the apparatus. The outlet end of valve plunger 38 is provided with a counterbore 50. On which a glass cylinder 52 is secured by suitable means. A marine capillary bore 54 is provided in cylinder 52, the bore diameter being chosen to provide the desired continuous flow rate through the apparatus in actual use and to damp out undesirable inlet pressure surges. At the bottom of counterbore 50, one or more radially extending passages 56 are provided which open into bore 24 on the inlet side of circumferential flange 48, to complete the continuous, low flow path through the apparatus. The outlet side of circumferential flange 48 is provided with a conical surface of geometry similar to that of valve seat 28.A resilient seal ring 58 of a material such as silicone rubber is captured between valve plunger 38 and seat 28. Ring 58 preferably is sized so that it moves with valve plunger 38 and is small enough in outer diameter to allow a desired second higher flush flow rate when valve plunger 38 is moved to the right, as illustrated. However, ring 58 also may be sized to fit snugly in bore 24 right at seat 28, in which case the inner diameter of the ring is sized to allow the second desired higher flush rate.

Finally, an auxiliary outlet passage 60 is provided through a boss having an attachment fitting 62, to which suitable pressure instrumentation is attached during use.

Figure 3 shows an elevational view, partly in section, of another embodiment 61 of a flow control device according to the invention. Here, the apparatus 61 is identical to the embodiment of Figure 2 except inlet passage 30 enters from the top and outlet passage 26 opens downwardly, as illustrated, into a plenum 66 bounded by downwardly depending, generally outwardly flaring circumferential wall 68. The lower edge of the wall 68 defines an annular lip 70 which is hermetically attached to a thin, flexible plastic diaphragm 72. Thus, liquid in plenum 66 causes, diaphragm 72 to flex in response to pressure changes. These changes are transmitted to a liquid on the other side of diaphragm 72. The pressure in this other liquid is monitored by a transducer, not shown, attached to the apparatus by a suitable fitting 74.For simple actuation of the apparatus to provide high flush flow, a flush lever 76 is slidably mounted on actuator shaft 40. A retaining finger 78 extends from housing 22 into a bore 80 in lever 76, to keep the lever in position for convenient actuaction.

In operation, apparatus 10 as shown in Figure 1 is connected to receive liquid through inlet passage 30. The force of this fluid flow in passage 30 keeps control valve member ;y5 in contact with inlet passage valve seat 33 thereby partially restricting the flow into bore 24. This partially restricted flow rate is, however, always greater than that needed to provide for a continuous flow at the low flow rate for the device. The liquid then flows from bore 24 through passages 56 and through capillary bore 54 and then out outlet passage 34.

When used in the fast flush mode or second higher flush rate such as to speed flushing of air from the device prior to insertion of the catheter in a a patient, actuator shaft 40 is moved to the right, as illustrated, thus permitting fluid to flow around valve plunger 28 and thereby allowing for larger flow rate to sweep air from the apparatus. Once the apparatus has been flushed and the catheter has been inserted into a patient, slow continous flow rate is provided using capillary bore 54.

Periodically, to ensure that the indwelling end of the catheter does not clog, the actuator rod 40 is moved to activate the fast flow mode to provide a short, high burst of fluid through the system, thereby dislodging and sweeping away any undesirable particles. This fast flush flow mode can cause the generation of bubbles of air in the drip chamber of the measurement system if the flow rate is too high. It is the flow control means 35 in the inlet passage that prevents too high a flow rate from occuring. The inlet flow control means provides for allowing sufficient flow rates for the normal flow rate and additionally to allow for the second higher flush rate, but the flow control does not allow the high flush rate to be of such magnitude so as to cause air bubble generation in the system. That is, the flow control means is calibrated to allow for fast flushing or dislodging of undesirable particles but not so high as to cause the generation of bubbles in the air chamber. In the event that an air bubble becomes lodged in the apparatus, the apparatus can be disconnected from the system and inverted, if necessary, (see Figure 3) so that ball member 35 moves out of engagement with valve seat 33 and rests on retaining ring 37 to allow removal of the air bubble. Without this feature of the retaining ring to maintain the ball member in the inlet and still provide a high flow rate the apparatus might well have to be discarded if such a bubble were to form.

In use, the apparatus of Figure 3 operates virtually identically to that of Figure 2. High flush flow is easily provided with one hand by gripping housing 22 and lever 76 between the thumb and forefinger and squeezing. Due to the downwardly flaring geometry of plenum 66 and the location of outlet passage 26 at the upper end thereof, air in plenum 66 is quickly and efficiently flushed from the device prior to insertion of the catheter into the patient. Also since the flush flow and the low flow are directed generally parallel to diaphragm 72, no unwanted distortion of the diaphragm results due to flow effects.

As various changes could be made in the above apparatus without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense. For example, a flapper valve type construction might be used for flow control in the inlet passage.

Claims (15)

1. A flow control apparatus for use in liquid flow systems for pressure monitoring of haemodynamics, such systems including a catheter which is continuously flushed in use, said apparatus comprising: a housing having at least one passage therein, said passage having an inlet and an outlet; a valve seat defined in said passage; a valve plunger resiliently mounted in said ,passage in contact with said valve seat; marine bore capillary means extending at least partially through said plunger for providing a low flow path from said inlet to said outlet when said valve plunger is in contact with said valve seat; and means for selectively moving said plunger out of contact with said valve seat to provide a high flow path around said plunger from said inlet to said outlet.

2. A flow control apparatus according to claim 1, wherein said housing comprises a plenum extending downwardly from said at least one passage, said plenum having a flexible lower diaphragm wall; and further comprising means located exteriorly of said diaphragm for attaching a pressure sensing device.

3. A flow control apparatus according to claim 2, wherein said plenum comprises downwardly extending, essentially smoothly flaring side walls, whereby gas trapped in said chamber is caused to rise in said plenum as it fills with liquid, to be flushed from the apparatus through said outlet.

4. A flow control apparatus according to claim 1, wherein said valve plunger comprises an essentially cylindrical body with an essentially radially extending circumferential flange thereon, a counterbore extending axially through said cylindrical body, said capillary means being mounted in said counterbore, and at least one passage extending from said counterbore outward to an exterior surface of said cylindrical body.

5. A flow control apparatus according to claim 4, further comprising a resilient seal element positioned between said circumferential flange and said valve seat.

6. A flow control apparatus according to claim 1, wherein said valve plunger comprises an axially extending actuator shaft slidably mounted in a hole extending into said housing, further comprising a resilient element mounted around said shaft between said valve plunger and said housing.

7. A flow control apparatus according to claim 1, wherein said moving means comprises an axially extending actuator shaft attached to said valve plunger, said shaft being slidably mounted in a hole extending into said housing.

8. A flow control apparatus according to claim 7, further comprising a contact button mounted on the end of said actuator shaft extending outside said hole and lever means mounted on said housing in position to cooperate with said button to move said valve plunger out of contact with said valve seat.

9. A flow control apparatus according to claim 5, wherein said seal element is a resilient ring having an outer diameter sized to permit flow of liquid through said passage when said valve plunger has been moved out of contact with said valve seat.

10. A flow control apparatus according to claim 5, wherein said seal element is a resilient ring having an inner diameter sized to permit flow of liquid through said passage when said valve plunger has been moved from contact with said valve seat.

11. A flow control apparatus according to any of the preceding claims wherein said inlet has flow .control means to limit the amount of flow in the high flow path thereby to minimize the possible production of air bubbles in the system.

12. A flow control apparatus according to claim 11, wherein said flow control means includes a second valve seat and a ball member arranged for cooperation with the second valve seat.

13. A flow control apparatus according to claim 12, wherein said inlet has a retaining means for holding said ball member.

14. A flow control apparatus substantially as herein described with reference to Figure 2 or Figure 3 of the accompanying drawings.

15. A haemodynamics pressure monitoring system incorporating a flow control apparatus according to any of the preceding claims.