CA1279705C - Disposable pressure transducer for use with a catheter - Google Patents

Abstract

ABSTRACT

A disposable blood pressure transducer system for use with a catheter with or without a catheter flush/flow valve. The transducer housing has both electrical and fluid connections, with the electrical connections being protected from contamination by fluid.

Description

GCC-281 -2~

catheter is inserted into the blood vessel to the point of interest. Saline solution is then typically infused through this catheter in order to provide a medi~m for the transmission of pressure waves through s the catheter to a transducer element located outside the body.

Traditionally, pressure transducers have been reusable elements involving some sort o strain-sensitive resistive wires or semiconductor elements bonded to a diaphram which contacks the pressure transmitting fluid. However, such reusable pressure transducers introduce the possibility, over time, of contamination and deterioration of the delicate trans-ducer elements. Repeated sterilizations~ dally wear and tear such as temperature variation, pressure vari-ation, impact, and vibration, may all con~ribute ~o reduced sensitivity, linearity, accuracy, and life of such a reusable device.
In order to overcome the deficiencies of reusable pre~sure transducers, there have been devel-oped disposable pressure transducers. Such disposable transducers have several advantages over the reusable type including the necessity to sterilize each unit only once, the reduction in handling, wear and tear, the avoidance of environmental variations in repeti-tive usage, and the enhanced electrical characteris-tics of a single use element solid state transducer.

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Among the disposable blood pressure transdu-cing elements commercially available are those manu-factured by Cobe Laboratories, Inc., Gould, Inc.
Norton Company, Sorensen Research Company, and Health~
dine Cardiovascular, Inc.

Of the commercially available models, all are generally used by mounting on a bedside vextical pole directly below a saline source, typically a ster-ile plastic bag. Fluid connections are typically made with Linden fittings which are either molded as part of the device housing or attached to short lengths o~
plastic tubing. Alternatively, fluid connections may be made with Luer-lock fittings and some units may be mounted on the upper arm of the patient by using a strap and special mounting base.
Most commercially available disposabl e pres-sure transducers are connected to their associated monitorlng electronics through an attached short length of electrical wire terminating in a connector.
~; This wire is generally refered to as a ~pigtail."

Because pressure transducers are typically mounted on a bedside pole directly below a saline source, isolation of electrical connectlons from the saline solution is especially important. A short-coming of those units lacking a pigtail connection is , ~j," -. . ~ ~ . ' .
' ., ' ' ' ' ~CC-281 -4-their susceptibility to damage from saline exposure, either during installation, or during operation due to leaking connections. Such damage may not be external-ly evident to the attending professionals but rather may affect the accuracy and reliability of the trans-ducer elements, thereby exposing the patient to un-necessary risk. In those units having a pigtail, electrical connections may be made to the unit after its installation on the pole. However, such units are often equally susceptible to leaking connection~ since fluid can travel down the pigtail and invade the connector.
Typically, these disposable transducers are associated with, and in some cases are made integral with a catheter patency flush/flow valve assembly and housing, through which saline solution is infused through an in-dwelling vascular catheter at a selec-tively controlled rate.
- It is the general objective of the present invention to provlde a disposable pressure transducer system, for continuous blood pressure monitoring, which is less susceptible (than those heretofore available) to fluid contamination of electrical con-nections.

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srief Description of the Invention The invention consists of the provision in a pressure transducer unit for blood pressure monitoring having a housing which includes on its external surEace, Eirst and second fluid ports, and an electrical connection port, said housing including a fluid flow path between said fluid ports, said electrical connection port containing a first electrical connector electrically isolated from said fluid flow path, pressure transducer means positioned in pressure sensing communication with said fluid flow path for developing a signal representative of the pressure of a fluid in said fluid flow path, means for removably connecting and disconnecting fluid input and output connections to said fluid input and output ports and means for removably connecting and d-~: nnecting a second electrical connector to said fi~.t electrical connector within said housing, the improvement consisting of: (a) splash curtain means for preventing movement of fluid, external to said housing, from the space surrounding said fluid input and output ports to the space surrounding said electrical connection port, wherein said splash curtain means comprises a barrier wall located on the exterior of said housing and interposed between said fluid ports and said electrical connection port, adapted for deElecting fluid, which may escape from said fluid ports, away from said electrical connection port.

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Figure 1 is a perspective view of a first embodiment of the present in~ention.
Figure 2 is a rear view of the Figure 1 embodiment of the present invention.
Figure 3 ls a partial cross-sectional view taken along line 3-3 of Figure 1 with an associated cable and plug.

Figure 4 is a front view of a second embodi-ment of the present invention.
Figure 5 is an exploded perspec~iv~ view of the Figure 4 embodiment of the present invention.
Figure 6 is a partial vertical-sectional view of the transducer housing of a third embodiment of the present invention.

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~a~ Pescriptio.B o~ ~;h~ In~n~i~
Referring now to Figures 1 and 2, there is shown a pressure transducer system catheter fl ush/fl ow val ve assembly constructed in accordance with the pre-sent invention. In operation, the entire assembly depicted in Figures 1 and 2 would be clamped to a pole and held ~ecurely in place by a separate gripping member clamped about a flange 12 on the backside of splash curtain lO or about flange 12a on the bottom of curtaln lO. Curtain lO carries catheter flush/flow valve housing 16 having fluid inlet port 33, fluid outlet port 35, an internal fluid flow path between inlet port 33 and outlet port 35, and electrical con-nection port 31 isolated from the fluid flow path.
A source of saline solution usually mounted above the transducer/flusher on ~ vertical pole or optionally including an inusion pump mounted re~otely is connected to fluid inlet port 33 and 10ws in either a 810w flowmode or a flushingmode through the flusher and exits at fluid outlet port 35 which is connected to a catheter. The position of a manual actuator 3g of a valve, at a location in the valve housing identified by reference numeral 37, regulates the flow rate of fluid flowing from fluid inlet port 33 to fl uid outl et port 35. Actuator 39 is spring-biased into a position permitting only slow fluid : . .
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flow. By pushing actuator 39 inward (to the right in Figure 2~, the valve opens to permit a faster flushing flow.

At the 1 ef tward end (as shown in the fig-ures) o~ housing 16 is tran~ducer housing 300 in which is located a pressure transducer means (not shown in Figure 1) positioned in the fluid flow path between fluid inlet port 33 and fluid outlet port 35. The pressure transducer means and its operation will be considered in greater detail in connection with Figure 3.

Curtain 10 comprises front surface 13~ top fla~ge 11, a pair of side flanges 17 (only one is show~in in Figure 1) and curtain mounting flanges 12 and 12a. As will be appreciated from the figures, curtain 10 is designed to deflect fluid impinging upon it from the top or front away ~rom its rear surface at which electrical connection port 31 opens. Shielding of electrical connection port 31 from fluid which drops f rom a saline solution bag or connecting tubes is accomplished by mounting housing 16 on splash cur-tain 10 with the openings to fluid ports 33 and 35 on one side of the curtain and the opening to electrical connection port 31 on an opposite side of the ourtain.

: ~ ' . ' " ' 7(~5 Referring now to Figure 3~ one see , in æec~
tion, the left hand end of housing 16, transducer housiny 300 and pressure transducer means as described more fully below. A cable 40 conducts the transducer signal to a remote blood.~pressure indicating instru-ment. Housing 300 is sealingly secured (such as by a sealing adhesive) to splash curtain 10 by means of a mounting flange 30 which is a part of housing 300 and fits within a corresponding opening in the curtain, so that electrical connection port 31 pr-otrudes from the back surface of curtain 10.

Within transducer housing 300, transducer 14 is mounted on transducer circuit card 310. Card 310 includes associated equalization circuitry necessary for operation of the transducer and slide-on connector leads tnot shown) at the end 311 of card 310 distal from transducer 14.
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Circuit card 310 is adhesively bonded to le~twardly facing inner surface 320 of housing 300.
Surface 320 includes pressure transmitting port 321, by which transducer element 14 is coupled, for pres-~- sure sensing, to the ~luid flowing from inlet port 33 25 to outlet por~ 35. Pressure transmitting cylindrical plug 305 (a silicone gel in this embodiment of the invention), sealingly disposed in port 321, effects electrical isolation of electrical connection port 31 from the fluid flow path in housing 16, while eec-' ::.

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GCC-2~1 -10-ting a pressure sensing ~or transmitting) communica-tion between transducer 14 and that fluid path. Plug - 305 is suitably opaque to reduce light-sensitive ef-fects present in the transducer~ Transducer 14, in thi~ embodiment of the invention, comprises a micro-machined silicon diaphragm device in which electrical characteristics change in response to changes in the pressure in the medium being sensed and with which the device is in physical contact.
Electrical connection port 31 is in the form of a barrel shaped socket. End 311 of circuit card 310 extends into this socket and presents sliding contact points (not shown) which are engaged when a mating cable connector 15 at the end of cable 40 is fitted over the socket. Cor,nector lS has a cylindri-cAl recess within its body 20 which is tightly fitted over the outside surface of socket 3~ Located at the rear end of the cylindrical recess is an 0-ring 2~
which is engaged by the edge of socket 31 and prevents fluid entry into the interior of the cable connector when it i8 secured in position on socket 31. A detent ring 32 on socket 31 engages a groove 38 in cable connector 15 as the connec~or is fitted over the socket. This engagement maintains the relationship between the connector and the socket and thereby con-trols the sealing compression of 0-ring 21. At its distal end, cable ~0 transmits the transducer signal to a remote blood pressure indicating instrument.

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~ ~7~3~ r-Within connector body 20 is housed a pair of floating connector members 219 and 215 which cooperate to create a reliable electrical connection between the sliding contact points of circuit card 310 and the wires in cable 40. Connector body 20 is entered at its rear-most end by cable 40 which is provided with a water-tight elastomeric seal and strain relief means 43. me conductors within cable 40 are separated into a plurality of wires of which wire 46 is but one.
These wires are a~tached to a plurality of electrical contact members of which 217 is but one~ Electrical contac,t member 217 is carried upon connector member 219 and is opposed by connector member 215. Both connector member 215 and connector member 219 are carried within a pair of mating recesses 271 and 273 fonmed by a flange 272 of connector housing 20. It should be noted that connector members 219 and 215 are allowed a small degree of freedom to move within connector body ~0 and thus adjust to imperfections and variations of position of circuit card 310.
When connector 15 is attached to socket 31, air is trapped within the connector~ the socket and housing 300 containing transduc~r 14, thereby creating a pressurized environment. Unless vented, such a pressurized environment would provide an incorrect indication of pressure. Housing 300, in the vicinity of transducer 14, therefore, has a vent port filled : , .

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with a vent plug 340 which is composed of a porous hydrophobic materlal. Vent plug 340 permits pressure equilibration with atmospheric pressure in order to assure accurate readings while preventing the entry of aqueous fluids into the vicinity of the transducer or its associated electronics and connectors~

Cable connector 15 carries a protective cap 25 which provides further protection against entry of fluid into the interiox of the connectort ~ap 25 is mounted on connector 15 for pivotal movement between an open position, as shown in Figure 3, and a closed position in which the cylindrical recess within the connector body is closed by the cap. Cap 25 pivots about the axis of a pin 112 which passes through a pair of spaced extension~ 114 on the cap (only one is sho~n in Figure 3) and a pair of spaced supports 115 on the connector (only one is shown in Figure 3). A
spring 110 biases cap 25 to cover the cylindrical re~ess within the connector body when the connector is disconnected from socket 31. While the connector is connected to socket 31, protective cap 25 is retained : in its open position by a retaining post 100 which extends away from the rear surface of curtain 10 and engages the cap. Upon removal of connector 15 and disengagement of cap 25 from post 100, spring 110 urges the cap to move to the closed position ~counter-clockwise in Figure 3) and seal off the opening into the recess in the connector. This is accomplished by ': ' , . ' :
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an O-ring 27 which is carried by the cap as the O-ring is compressed against the open end of connector body 20. When cable connector 15 is being connected to socket 31, protective cap 25 is retracted against the action of spring 110 and held in place by the user's thumb until the desired connection is made and post 100 engages the cap.
For further protection against entry o~
fluid into the interior of socket 31, the trans-ducer/flusher unit is supplied with a disposable elas-tomeric cap 116. Cap 116 is removed from socket 31, as shown in Figure 3, so that cable connector 15 can be connected to socket 31.
Referring now to Figures 4 and 5, there is shown an alternative mounting for the transducer/
flusher of the present invention. As depicted in Fig-ures 4 and 5, curtain 10 of Figure 1 is replaced by a mounting base 400. The entire transducer/~lusher assembly is removably mounted on base 400 which is then secured in position directly on the patient being monitore~ ~ypically, base 400 i~ secured by a strap having an oppo~ing hook and loop clo~ure (e.g.
"VELCRO") means 500 which is passed continuously through a pair of slots 410 and 415 in base 400. The entire transducer/ ~lusher assembly is retained in place on base 400 by its insertion into a mounting plate 430 which has a central opening 432 for receiv-. .
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~CC-281 -14-ing a cylindrical projection 330. In addi~ion, a pair of opposing ja~s 420 and 425 resiliently retain a flange 38 surrounding actuator 39.
It should be noted that in thi~ patient mounted con~iguration, the relative orientations be-tween electrical socket 431 and ~luid outlet port 435, as depicted in Figure 4, are different from the rela-tive orientations of electrical socket 31 and fluid outlet port 35, as depicted in Figure 1. In Figure 1, socket 31 and outlet port 35 are at a right angle to one another, while in Figure 4 the two extend parallel to one another in opposite directions. In addition, luer fitting 33 of the pole mounted ver~ion o~ Figure 1 i8 replaced by a short length of hollow tubing 433 which may terminate in a luer fitting~ Tubing 443 may be of such a length as to displace its fluid connec-tion from the region of flange 30~ Alternatively, tubing 433 may be flexible to allow it to be displaced - 20 out of the region of flange 30. Finally, cap retain-ing post 100 of the pole mount version is present as post 440 of the patient mounted version.
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In all other respects, the patient mounted version of the present invention is identical to the pole mounted version and contains elements as depicted in Figures 1-3.

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~ 7 The third embodiment of the present inven-tion, shown in Figure 6~ is generally similar to the first two embodiments but differs in not having a valve for regulating fluid flow between an inlet port 633 and an outlet port 635. Fluid flow is fixed, insofar as the transducer system is concerned, by the dimensions and characteristics of the inlet and outlet ports and the fluid flow path.

As in the embodiment o Figure 1, the Figure 6 embodiment includes transducer housing 301 ~s~milar to housing 300) and mounting flange 30, behind which is located an electrical connection port (31 in Figu~e 1, but not seen in Figure 6). ~ousing 301 differs from housing 300 in that housing 301 includes a clo-sure wall 600 at its rightwardly facing end (as seen in the figures) rather than being open to the fluid passageway in a flush/flow valve assembly.

It should be pointed out that the embodiment shown in Figure 6 also may be used by closing o~
fluid outlet port 635 and connecting fluid inlet 633 to the leg of a "T" section coupling with saline solution flowing through the top of the "TN section coupling. In such a case, the transducer measures the static pres~ure built up in the line running from the "T" section coupling to fluid inlet port 633.

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Having described the invention with respect to certain embodiments, it should nonetheless be un-derstood that other conf igurations wil 1 be apparent to those skilled in the art. It is intended therefore that this invention be defined by the claims which follow so as to encomp~ss all o~ those variations within the true spirit and scope of the invention.

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Claims (7)

1. In a pressure transducer unit for blood pressure monitoring having a housing which includes on its external surface, first and second fluid ports, and an electrical connection port, said housing including a fluid flow path between said fluid ports, said electrical connection port containing a first electrical connector electrically isolated from said fluid flow path, pressure transducer means positioned in pressure sensing communication with said fluid flow path for developing a signal representative of the pressure of a fluid in said fluid flow path, means for removably connecting and disconnecting fluid input and output connections to said fluid input and output ports and means for removably connecting and disconnecting a second electrical connector to said first electrical connector within said housing, the improvement consisting of:
(a) splash curtain means for preventing movement of fluid, external to said housing, from the space surrounding said fluid input and output ports to the space surrounding said electrical connection port, wherein said splash curtain means comprises a barrier wall located on the exterior of said housing and interposed between said fluid ports and said electrical connection port, adapted for deflecting fluid, which may escape from said fluid ports, away from said electrical connection port.

2. A pressure transducer unit according to claim 1 wherein said splash curtain means includes means for attachment to a pole.

3. A pressure transducer unit according to claim 2 wherein said means for attachment to a pole include a vertically extending mounting flange.

4. A pressure transducer unit according to claim 2 wherein said means for attachment to a pole include a horizontally extending mounting flange.

5. A pressure transducer unit according to claim 1 further including a connector housing associated with said second electrical connector, said connector housing and said electrical connection port of said pressure transducer housing including fluid seal means adapted for preventing fluids from entering said electrical connection port.

6. A pressure transducer unit according to claim 5 wherein said fluid seal means includes a connector housing containing an O-ring.

7. A pressure transducer unit according to claim 5 wherein said fluid seal means includes a cap adapted for protecting said second electrical connector from fluid contact when said first electrical connector is disconnected from said electrical connection port of said pressure transducer housing.