AU2450202A - Pressure transducer apparatus with disposable dome - Google Patents

Description

13. MAR. 2002 16:58 SPRUSON FERGUSON 61 2, 92615486 NO. 4733 P. 4 S&F Ref: 480196D1

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Sunscope International, Inc.

Suite 115, 20250 Acacia Street Newport Beach California 92660 United States of America John E. Schulze Spruson Ferguson St Martins Tower,Level 31 Market Street Sydney NSW 2000 (CCN 3710000177) Pressure Transducer Apparatus with Disposable Dome Invention Title: The following statement is a full description of this invention, including the best method of performing it known to me/us:- [R:\LIBW]47444.do;:keh 13. MAR. 2002 16:58 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. PRESSURE TRANSDUCER APPARATUS WITH DISPOSABLE

DOME

Background of the Invention The present invention relates to medical fluid pressure transducers, and, more particularly, to fluid pressure transducers for invasive blood pressure measurements having a reusable component and a one time use disposable component.

Since the 1970s, physiological blood pressure monitoring became widely 0 employed for diagnosis and treatment of patients experiencing hemodynamic instability during surgery and in other forms of acute illness. An arterial cannula, central venous catheter, or pulmonary artery catheter is inserted into a blood vessel using a Seldinger percutaneous puncture technique, the puncture wound is dilated, then the catheter is inserted into the vessel, the catheter is attached to a saline-filled 15 pressure monitoring line, blood pressure transducer, pressurized fluid supply,' and sterile fluid flushing device, and finally the transducer's electrical interface cable is attached to an electronic blood pressure amplifier and display monitor. Once calibrated, such systems give accurate and up to date readouts of the constantly changing blood pressure levels at the tip of the catheter within the cardiovascular 20 system.

Similarly, catheters and techniques have been developed for direct insertion of fluid filled catheters into the brain for the monitoring of increased intra-cranial pressures resulting from acute brain injury, and for insertion into the uterus during childbirth to monitor the strength and character of contractions through changes in the amniotic fluid pressure. Many of these same prior-art transducer systems have been and continue to be employed for this entire range of measuring applications, plus other physiological monitoring or biological fluid pressure measurement applications within living bodies.

A typical early prior art device includes a removable (single use disposable) dome with an inlet and an outlet port for flushing and filling of the transducer 13. MAR. 2002 16:58 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 6 assembly with sterile isotonic saline solution. The dome is made of a clear molded plastic material such as polycarbonate so that air bubbles in the flushing fluid could be observed and removed. A flushing device, such as ones described in US Patents 4,291,702 to Cole or 3,675,891 to Reynolds is typically affixed to the dome's side port for the purpose of providing a continuous flow of saline through the dome and into the catheter. A "fast flush" valve on the flush device may be activated to temporarily select a higher flow rate for filling, de-bubbling, or clearing of blood in the dome and/or catheter.

The early prior art blood pressure transducers were made with a metal diaphragm forming a pressure sensitive area on an external surface of the transducer .o housing. The diaphragm was coupled internally to a mechanical push rod linkage assembly and a strain-sensing device, such as an unbonded wire strain gauge constructed in a Wheatstone Bridge configuration. The pressure sensitive area of the metal diaphragm is now typically isolated from the sterile saline being flushed into the 15 catheter by a thin polycarbonate or nitrile rubber diaphragm on the mating surface of *a single use dome. Such disposable domes are typically supplied sterile and discarded after a single use to avoid a biological contamination risk to the patient. The mating reusable transducer portion, which is not in direct contact with the patients' blood, is frequently wiped down with alcohol or placed in a chemical sterilant after each use 20 and then reassembled to a new, sterile dome for subsequent uses. In the late several physiological pressure transducers systems were developed using semiconductor strain sensors, but still employing a mechanical linkage and a metal diaphragm, for example the Statham P50 and the Bentley M800. The strain sensing element is a silicon beam which is bonded to the transducer body in such a way that strain is applied to the beam when the diaphragm is flexed. In these designs, the Wheatlsone bridge was ion-implanted directly into the silicon beam and the output signals were calibrated using discrete resistors located in the transducer's electrical interface connector. In other respects, these "transitional" art transducers were typically connected to catheter/manometer fluid systems in the same manner as described above.

13. MAR. 2002 16:58 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 7 In the early '8Os, non-reusable (disposable) transducmrs were developed using improved semiconductor strain gauges made from a silicon chip containing an etched diaphragm used in combination with laser-trimmed thick film resistor network for temperature and span compensation of the sensor chip, as is fully described in US Patents 4,576,181, and 4,291,702, 4,557,269, 4,683,984, 4,679.567, 5,042,495, 4,776,343, 5,097,841. Further, the development of thin film "on-chip" compensation methods at Motorola (see US Patent 4,465,075) allowed the development of even smaller, simpler disposable transducer designs as are more fidly described for example in US Patents 4,539,998, 4,679,567, and 4,825,876. Importantly, all of these disposable transducer designs except those of Cole and Kodama appear to have abandoned the mechanical linkage in favor of a hydraulic pressure coupling medium :0• 00 •comprised of a silicone elastomer, or "silicone gel", for examplo as cited in US Patent 4,529.789. These elastomers, which had become common in the semiconductor industry for protecting chips from ambient fluids and vapors, are used to form a good 15 electrical barrier between the chip and the saline solution, while imparting greater m.,.echanical ruggedness and over-pressure characteristics to the sensor, plus transmission of the hydrodynamic signal. In medical use, the gel is juxtapositioned between the catheter flush solution and the transducer chip, thus conveying the hydraulic pressure signal directly to the chip's integral sensing diaphragm while 00 op20 isolating it electrically from the conductive and corrosive effects of the saline solution.

The entire transducer assembly, including the chip are typically sold to be discarded after a single use, since the internal components can not be adequately cleaned for resterilization or reuse.

Disposable transducer designs employing semiconductor strain gauge sensors and gel coupling media as just described are desirable because they provide a relatively straight fluid channel which is' easy to fll with sterile saline without turbulence or accumulation of bubbles. Further, they do not require twist-on attachment of a separate disposable dome as the prior art re-usable designs do. and they 're highly rugged and accurate due to the gel pressure transmission media and silicon chip micromachined sensor strucmre. However, manufacturing costs remain 13. MAR. 2002 16:59 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 8 high. The single highest cost component is the pre-calibrated semiconductor chip and associated wiring, which typically must be discarded after a single use.

With the objective of further reducing medical costs and medical wastes accordingly, there is a need for a re-usable physiological pressure transducer which employs an inexpensive semiconductor strain gauge sensor which has been produced by current high volume silicon micro-machining and chip carrier production techniques. Wallace (US Patent 4,610,256) and Frank (International Application PCTfIUS5/01957) disclose pressure transducers employing thick-film trimmed silicon strain gauge sensors attached to a transducer body filled with sificone oil. The exterior of the transducer body carries a pressure sensitive area covered by a flexible diaphragm which communicates hydraulic signals to the chip sensor through the silicone oil-filled body and through a hole filled with a pressure tram issive fluid.

.which is respectively gel or oil to an opposing exterior surface. In these designs, the silicon chip sensor and compensation circuitry is carried by an exterior opposed surface of the transducer body. In both of these examples, the mating disposable dome contains a flexible sterile isolating diaphragm according to the disposable dome prior art which is intended for one time use. Adams, et al. (US Patent 4,686,764) discloses a gel-filled pressure transducer body containing a thin film-trimmed chip sensor. The silicon chip sensor is located inside the body and the pressure sensitive 20 area on the exterior of the transducer consists of a flexible polymer membrane such as polyamide which transmits the hydraulic pressure signal through the gel and thus directly to the sensor without need for a coupling channel, Frank (US Patent 4,920,972) discloses a blood pressure transducer comprising a gel-filled body with a chip sensor again located on the outside of a body and hydraulically coupled to the diaphragm through a tapered hole filled with gel. The transducer diaphragm covering the pressure semitive area on the opposing side of the body is a flexible material such as silicone rubber. A disposable dome of thc prior art type using a flexible interface membrane is used to isolate the sterile saline from the transducer.

In spite of these improvements nonetheless, the prior art transducers still suffer from certain drawbacks. The disposable transducers remain expensive to produce because of the high cost of throwing away the micromachined chip and wiring. The 13. MAR. 2002 16:59 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 9 diaphragm of the earlier prior art re-usable transducers disclosed by Wallace and Frank can be easily punctured resulting in leakage of the pressure transmitting medimn and failure of the transducer. While the re-usable transducers as later disclosed by Adams and Frank offer a significant improvement in mechanical ruggedness because of the use of silicone gel as the hydraulic coupling medium, the fluid path inside the dome is tortuous and still more difficult to setup, fill and de-bubble because the membrane-type dome is large in relation to the diameter of the inlet and outlet ports, and it must be attached and filled with saline prior to use. In practice, small bubbles often attach themselves in the sharp corners adjacent to the edges of the diaphragm, thus reducing the dynamic response of the transduced pressure signal.

Therefore, it would be highly desirable to develop a disposable dome for a reusable transducer application employing a fluid path without sharp corners, for instance, in the vicinity of the diaphragm, where bubbles are easily entrapped in current designs It would also be highly desirable to develop a disposable dome structure for a re-usable transducer which has a more-or-loss straight through fluid Sfilling path to minimize the time and difficulty required to clear the system of air toat,.,o bubbles. It would also be desirable to reduce manufacturing cost and complexity of the medical reusable transducer design by placing the sensor chip directly inside the transducer body in communication with pressure hydraulic transmitting medium. And finally, in the prior art devices of the re-usable type, there is no physical barrier to prevent the medical practitioner from touching the non-sterile pans of the transducer wie attending to the patient. It would be highly desirable to develop a means for isolating the non-sterile (reusable) pans from the sterilized parts normally manipulated by the medical practitioner during blood drawing and readjustment and calibration of the catheter and monitoring system components. These and other objects and advantages of the present invention will be apparent from the attached drawings and the description of the preferred embodiments which follow.

13. MAR. 2002 16:59 SPRUSON FERGUSON 61 292615486 10. 4733 P. Summary of the Invention There is firstly disclosed herein a disposable dome for use in combination with a reusable sensor to form a reusable transducer assembly for measuring pressure in a fluid line coupled to a catheter inserted into a living body for making direct pressure measurements in areas within the body of medical interest, said disposable dome including a fastener arranged to releasably engage a complementary surface on the reusable sensor and discardable after a single use, said dome including an electrically and biologically isolating coupling media shaped in conjunction with the dome to form a straight through fluid filling path, and wherein said media transmits hydraulic pressure signals from a fluid-filled chamber in said dome to the reusable sensor, There is further disclosed herein a disposable dome for use in combination with a reusable sensor to form a reusable transducer assembly for measuring pressure in a fluid line coupled to a catheter inserted into a living body for making direct pressure measurements in areas within the body of medical interest, said disposable dome portion 715i including a fastener arranged to releasably engage a complementary surface on the reusable sensor and discardable after a single use, said dome including an electrically and biologically isolating coupling media shaped in conjunction with the dome, said assembly comprising a housing, an inlet and an outlet port in the housing, having a fluid flow path extending therebetween, and a cavity in the flow path, said cavity being divided into a first chamber and a second chamber by a flexible diaphragm, wherein said coupling ***media is disposed adjacent to said diaphragm to transmit hydraulic pressure signals from said first chamber to said second chamber via said diaphragm, said coupling media not comprising a diaphragm, and comprising one or wore elastozuers which form a smooth internal path for the flow of fluid.

There is further disclosed herein a method of monitoring a physiologic pressure, comprising the steps of: providing a patient having a catheter in communication with a fluid--carrying vessel within the patient; providing a one time use disposable dome having a housing, a straight flow path through the housing and a hydraulic pressure signal transmitting media disposed in the housing between the flow path and a pressure signal transmitting surface exposed to the outside of the housing, said dome having at least a first snap fit engagement surface thereon; [t\LLLLJ 116 IG6Aciadoclab 13. MAR. 2002 17:00 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 11 providing a pressure transducer having a pressure signal receiving surface, and at least a second snap fit engagement surface; removably placing the first snap fit engagement surface in interlocking contact with the second snap fit engagement surface, thereby retaining the pressure signal s transmitting surface in pressure signal transmitting contact with the pressure signal receiving surface; placing the flow path in fluid communication with the patient by way of the catheter; and monitoring the physiological pressure detected by the transducer.

e 0 0 0 0 0 *0 o I%:\l.laULL] L 16i64pc.ilA,d ,c 13, MAR. 2002 17:00 SPRUSON FERGUSON 61 292615486 NO, 733 12 Preferably, the assembly comprises a housing which is provided with an inlet and an outlet port having a fluid flow path extending thereborween. A cavity in the- flaw path is.

divided into a first and second chamber by flexible' electrical isolating and pressure transmissive medias. The flow path provides communication between the first chamber within the housing and the inlet and outlet ports.

More preferably, the first chamber contains an isolating media, which transmits hydraulic pressure from fluid in the fluid flow path to the transducer. The isolating media also forms an electrical and biological barrier between the fluid flow path and the reusable transducer portion described next.

:The second chamber preferably contains a comnpensated pressure sensor spaced from the pressuire sensitive surface with one side of the pressure sensor sealingly disposed in communication with a vent hole on an interior surface of the transducer housing- The vent bole provides an ambient air pressure reference to a. first side of a pressure sensor. A pressure transmissive .media is disposed in the Second chamber for transmitting hydraulic pressure signals from the pressure sensitive surfatce to a second side of the pressure sensor. An electr-ical conductor~ is connected to the pressure sensor and extends through the housing for connection to an external blood pressure monitoring display.

Preferably, the housing is divided into a first and a second removably securable components. The first component contains the first chamber, the asoistiog media and the inlet and outlet ports,~ and is adapted to be removable and disposable after a.single use. The second component contains the pressure sensor 3 the electrical conductor, and the pressur transmnissive media. In one embodiment, the first component has at least a first interference engagement surface for providing a releasable interference 1s" fit with at least one second, complementary interference engagement surface on the second component.

Preferably, the isolating media comprises a silicone gel. In a preferred embodiment, the isolating media and the pressure transmnissive media are brought into direct or indirect pressure transmitting contact M~th each other when the first and second components are secured together. To minimize the risk of adhesion and transfer of gel uipon disassembly in the case of direct contact between the isolating -6- 13. MAR. 2002 17:00 SPRUSON FERGUSON 61 292615486 NO. 4733 P. 13 7 media and the pressure transinissive media, the isolating media and pressure transmnissive media are preferably made from differenit materials. Alternatively, a diaphragm is provided to separate the isolating media from the pressure transmissive media when the first and the second components are removably secured together.

s In accordance with another aspect of the present invention, there is provided a method of making a disposable dome for a reusable transducer, said disposable dome having an essentially straight through flow path produced by constructing an isolating media consisting of at least a preformed diaphragm wherein the diaphragmn has an outer mounting and retaining ing stnicture that is thicker in the vertical dimension than the ic thickness of the diaphragm's center portion, and wherein the retaining ring strcture is displaced in the direction of the reusable transducer, and wherein the counter opposed surface in contact with the disposable dome is flat or alternatively shaped to form a smooth internal flow path.

A releasable connector structure, such as complementary treads, snap fit, bier, :Is interference fit, press fit or others known in the art may be provided on the housing for releasably connecting the housing to a reusable transducer portion. The releasable connection between the housing and the reusable transducer is such that the second surface of the isolating media is placed in hydraulic prcssure communication wit the transducer.

In a preferred embodiment, the method comprises the additional step of forming the second surface of the isolating media into a convex shape in the area where it o transmits hydraulic pressure signals to the reusable transducer. The isolating media may be formed by placing a curable elastonier precursor in the housing in contact with the fluid flow pat to form the isolating media, and curing the elastomer precursor in place to produce an isolating media.

In accordance with a further aspect of the present invention, there is provided a method of monitoring blood pressure in a patient. The method comprises the steps of providing a patient having a catheter in communication with a blood vessel within the patient. A one time use disposable dome is provided, said dome having a housing, a flow a0 path through the housing and a hydraulic pressure signal transmitting media placed in the housing between the flow path and a pressure signal trasmitting surface exposed to the outside of the housing.put'LMa W~l.&ewM 13. MAR. 2002 17:00 SPRUSON FERGUSON 51 2 92615486 NO. 4733 P. 14 A pressure transducer having a pressure signal receiving surface thereon is further provided. The pressure signal transmitting surface on the housing is removably placed in pressure signal transmitting contact with the pressure signal receiving surface on the transducer. The flow path is placed in fluid communication with the patient by way of the catheter, and blood pressure signals detected by the transducer are measured.

Additional embodiments of one time use disposable domes, in combination with or separate from reusable pressure transducer assemblies axe also disclosed.

Further features and advantages of the present invention will become apparent 10 from the detailed description of preferred embodiments which follow, when considered S. 4" together with the attached drawings and claims.

Brief Descrition ofthe DrawinRs FIG. I is a simplified cross-sectional side view of an embodiment of the transducer assembly according to the present invention taken along the centerline of the fluid inlet and outlet ports.

FIG. 2 is a cross-sectional view of a trst preferred embodiment of the transducer assembly, again taken along the centerline of the fluid inet and outlet ports.

FIG. 3 is a front view of the transducer dome according to the present S 4' 20 invention prior to connection to a flush device, fluid-conducting tubing, or catheter.

FIG. 4 is a top view of a transducer assembly according to the present invention, showing a side view of the dome of FIG 3, to which the transducer has been installed.

FIG. 5 is a cross-sectional view of a transducer dome according to the present invention without the transducer installed. Instead, a gel contouring "dust" cap has.

been installed on the dome for the purposes of curing the gel into a preset convex shape at the transduccr/dome interface area.

FIG. 6 is an elevational cross-sectional view taken along the centerfines of the inlet and outlet ports of a second preferred embodiment of the present invention.

FIG. 7 is a top view of a second preferred embodiment of the disposable dome portion.

13. MAR. 2002 17:01 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. FIG. 8 is an exploded perspective view of the assembly parts comprising yet a third preferred embodiment, wherein the support plate has been made part of the reusable portion of the transducer assembly and the clear molded dome portion includes an attachment and retention structure and sterile shield.

FIG. 9 is a schematic illustration of a typical pressure measuring system for fluid flushing and continuous measurement of pressures in a single catheter according to the present invention.

FIG. 10 is a perspective view of a fourth embodiment of the present invention as worn on a user's foreann; FIG. 11 is a cross-sectional view of the fourth embodiment of the present invention; FIG. 11 A is a close-up cross-sectional view of the portion of the. fourth embodiment of the present invention as defined by the arrow I A in FIG. II.

FIG. 11B is a close-up cross-sectional view of a portion of an alternate embodiment.

FIG 12. is an exploded, perspective view of the dome portion and reusable portion of the fourth embodiment of the present invention.

FIG. 13A is a side view of an IV pole mounting adaptor assembly which may be used in conjunction with the present invention.

20 FIG. 13B is a cross-sectional view of the IV pole adaptor assembly illustrated in FIG. 13A taken along the line 13B-13B, along with a horizontal cross-sectional view of a mating reusable transducer.

Detailed Description Figure 1 shows a first embodiment of the pressure transducer assembly, generally denoted by the numeral I. The assembly consists of two major parts, each with sub-pars which are mechanically connected together to form the transducer assembly 1. A first major part is the re-usable portion, generally denoted by numeral 2. Molded into the re-usable portion 2 are four electrical conductors 3, which convey electrical signals to and from the pressure sensor chip 4 through wirebonds 5. The electrical conductors carry insulating jackets 6, such that the electrical signals can be 13. MAR. 2002 17:01 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 16 conveyed away from the transducer assembly to a remote pressure monitor (not shown) without risk of shocks or shorts.

A second major part of the pressure transducer assembly is the disposable dome 7, which is detachable from the re-usable portion 2 and generally intended for one time use. The inlet fluid port 8, and outlet fluid port 9 are in fluid-flow communication with a first chamber 10 located inside the dome 7. The dome 7 contains a pressure-transmissive, but electrically and biologically isolating gel 1 I in first chamber 10 which on a first side is in contact with the flushing fluid filling said first chamber and said inlet and outlet ports, and additionally a second side of the gel is in contact with a diaphragm 12 coverfing a second chamber 13 both of which are part of said re-usable portion 2.

The diaphragm 12 is bonded to a raised annular ring 14 surrounding a recessed surface of the re-usable portion 2. The diaphragm is responsive to hydraulic pressure signals transmitted through the isolating gel I I from the fluid filling the fist chamber 9* 10. The diaphragm 12 thus conveys the hydraulic pressure signals into said second chamber 13, and then via pressure transmitting medium 15 to the pressure sensor chip 4. A pressure sensing surface of pressure sensor chip 4 is exposed to the pressure transmissive medium inside of" the second chamber 13. Preferably, the on-chip circuitry for the pressure sensor chip 4 includes predetermined gain and temperuture 9 920 compensation. In the illustrated embodiment, the chip 4 is sealingly attached to the floor of second chamber 13 disposed over vent hole 16 using a silicone rubber sealant 17 which is applied to the floor of the recessed surface on the re-usable portion 2 in a sealing ring surrounding the end of the vent hole at it's upper-most point proximate to the chip. Contrary to the teaching of the prior art medical reusable transducers, the hole is filled with ambient air and is intended to provide a continuous ambient reference pressure to one side of the sensor's internal diaphragm for proper referencing of the patient's fluid pressure measurements to ambient pressure.

A threaded cylindrical portion Is of the dome is releasably engaged into a mating threaded portion 19 of the re-usable portion when the two major portions 2 and 7 have been assembled for use. Friction enhancing structures such as a plurality of axially extending raised ribs 20 on the outer surface of the re-usable portion 2 allow 13 MAR. 2002 17:01 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 17 the re-usable portion to be grasped and turned in relation to the inlet and outlet ports 8 and 9 for assembly and disassembly of the pressure transducer assembly 1.

Figure 2 is a cross-sectional view of another embodiment of the transducer assembly as generally denoted by the numeral 1, again taken along the centerline of the fluid inlet and outlet ports 8 and 9. The re-usable portion as generally denoted by the numeral 2, includes a hub formed from elements 21 and 22. Rotating nut 24 is rotatably carried in an annular channel formed in the hub. Rotating nut 24 is provided with a plurality of radially inwardly facing annular threads for releasably engaging the 9: corresponding threads on the disposable dome 7. Any of a variety of alternate i0 releasable retention structures can be used as will be apparent to those of skill in the t"o" art, as long as the structure selected provides a sufficient compression to produce an Sadequate propagation of the pressure signal across the interface between media 15 and

I

The re-usable portion 2 further includes a cable jacket 25 containing four 15 insulated electrical conductors 26, 27, 28, 29 and sensor vent tube 30 (which is shown in cross section). The insulated electrical conductors 26 29 have their insulation removed at their ends terminating inside the re-usable portion 2, and the tinned ends of said conductors are soldered to sensor housing pins 31. To prevent shorts and increase fluid and corrosion resistance, the area generally denoted by the numeral o :20 is preferably filled with a potting compound such as silicone rubber. The sensor 9O o 9housing pins at their upper ends are molded into sensor housing 23, and terminate inside of second chamber 13, wherein they are connected to wirebonds 5. The wirebonds are connected to aluminum or gold pads on the pressure sensor chip 4, as is well known in the art. Thus the electrical signals are conveyed tolfrom the pressue sensor chip through wirnbonds 5, sensor housing pins 31, and insulated electrical conductors 26-29, and thusly to an external electrical interface connector, pressure amplifier and measurement display system (not shown). The pressure sensor chip 4 is sealingly attached to the interior surface of second chamber 13 using a silicone RTV 17, disposed over a vent hole 16, which is in communication with vent tube Thus, the air channel formed by vent hole 16 and vent tube 30 provides a continuous ambient reference to a first side of the sensor's internal diaphragm for referencing of 13. MAR. 2002 17:01 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 18 the patient's fluid pressure meammmenw to ambient atmospheric pressure. Second chamber 13 is filled with a pressure transmissive media 15, such as silicone oil, or preferably a cross-linked poly-dimethyl sioxane, for instance a platinum cure, two pert silicone gel available from Rhone-Poulene Visalox V-191.

A disposable dome portion generally denoted by numeral 7 of the transducer assembly I consists of a clear molded portion 34, incorporating inlet and outlet fluid chamels 8 and 9, in fluid flow communication with a first chamber 10, located inside the clear molded portion, a pressure transmissive but electrically and biologically isolating gel i I disposed in a recess in said first chamber, a threaded support plate 32, and rotating luer nuts 33. The rotating luer nuts provide a means of securely ooo connecting the inlet and outlet ports to fluid transmission tubing and a fluid-filled catheter inserted in a living body. The clear molded portion 34 is preferably molded o of n clear plastic material such as polycarbonate so that any bubbles or blood located in the fluid filling said first chamber 10 or said inlet and outlet fluid channels 8 and 9 can be easily observed and removed during the fluid filling setup process, as is well known in the art.

During manufacturing of the disposable dome portion 7, the clear molded portion 34 is ultrasonically welded, or solvent or adhesive bonded to the threaded support plate 32. The lower portion of the chamber thus formed (the first chamber 10) is filled with the isolating gel in an uncured state and the gel is cured and S9 contoured to form isolating gel I I as shall be fully described in conjunction with the description of Fig The isolating gel 11 is located between said fluid and said diaphragm 12, and thus provides an electrical and biological barrier between said fluid which is in communication with an invasive catheter, and the diaphragm 12, which presents a pressure sensitive surface on the re-usable portion 2. Diaphragm 12 is sealingly attached to an annular ring which forms an upper extension of second chamber 13, spaced from re-usable portion 2. For additional mechanical ruggedness and fluid reistance, the diaphragm is preferably a pressure formed polymer or rubber sheet and further extends across the entire upper surface of the re-usable portion 2 where it contacts disposable dome portion 7. The diaphragm is preferably made of a material 13. MAR. 2002 17:02 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 19 such as 2-10 mil thick polyisoprene, but it can also be formed from 302 stairless steel, nitrile or butyl rubber, high density polyethylene, Dupont Mylar, Teflon, or polyamide sheet, such as is sold under the brand name Capton@ or Upalon*.

Alternately, two dissimilar materials may be selected for said isolating and said pressure transmitting medias such that the two materials do not bond to one another during normal periods of contact in actual use. In such case, the pressure tnsmining medium could also form an integral diaphragm means This alternate embodiment of diaphragm 12 has been demonstrated by partially filling chamber 13 with a pressure transmitting medium such as cross-linked poly dimethyl siloxane, followed by a top eoo 10 layer of a single component primerless Dow silicone adhesive; Catalog No. 3-6611.

Once cured, the silicone adhesive sticks to the pressure transmitting medium and o.o.

forms a tough outer skin which is integral membrane 12. The cured adhesive is sufficiently different in composition and hardness from isolating gel I i that it can be used to contact the isolating gel II directly. Additional surface modifications of the pressure transmitting medium are also possible, such as electron beam deposition of an evaporatable metal such as silver in a vacuum to form a hardened and dissimilar surface which nonetheless is still effective in transmitting hydraulic pressure signals, As stated, the second chamber 13 is preferably filled with a pressure transmissive medium 15 such as a silicone gel. In the event the diaphragm 12 is 20 chosen from a material that is light transmissive, the silicone gel can include a filler such as carbon black in powder form which renders the pressure transmissive medium non-light transmissive as is well known in the art. Thus, light is prevented from entering the second chamber to affect the pressure readings produced by the pressure tranducer chip 4.

In clinical use, the pressure transducer assembly I is easy to assemble from reusable portion 2 and disposable dome portion 7. The re-usable portion, with it's pressure sensitive diaphragm 12 facing forward most, is advanced into the recess formed in the lower portion of the threaded support plate 32. As the re-usable portion is advanced, rotating nut 24 engages the mating threads of the support plate. Then the rotating nut is rotated a number of turns to fully advance the diaphragm 12 into contact with the isolating medium 11. During the advancement process, any air 13. MAR. 2002 17:02 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. contained between said diaphragm and said isolating medium is allowed to escape in the crevasses formed between the mating of said re-usable and disposable dome portions. As the diaphragm 12 contacts the isolating medium II flrstly at the diaphragms' center as shall be more fully described in conjunction with Figure 5. the isolating gel medium flows and deforms back in a controlled and uniform manner into the first chamber 10 to fully eliminate any remaining air betweon said diaphragm and said isolating medium. said remaining air escaping through the crevasses between aid re-usable portion 22 and the recessed portion of support plate 32. To prevent the diaphragm 12 from rotating and possibly upsetting the smooth and uniform contact with the isolating gel 11, the interior recess in support plate 32 which accepts the ':mating re-usable portion 22 can be optionally constructed in a non-round shape, or a guide channel and mating keyway can be molded into the subject mating parts to rotationally link hub component 22 with respect to the gel 11.

In Figure 3 is shown a front view of disposable dome portion 7 of the first preferred embodiment of the invention, showing the clear molded portion 34 of the dome, the topside of threaded support plate 32, inlet port 8, outlet port 9. first chamber 10, rotating luer nuts 33, raised ribs on luer nuts 20, support lands 36, diaphragm 12 (seen through clear molded portion of dome and isolating medium 11), fluid irdet channel 37, fluid outlet channel 38, a hidden view of the threaded portion o0 20 of the support plate 38, molded land areas 39 and 40 for attachment of self-adhesive labels.

Support plate 32 is molded of a non-transparent material such as colored polycarbonate, styrene or ABS. A clear molded portion 34, containing the inlet and outlet fluid channels 37 and 38 and rotating luer nuts 33 is affixed to the top surface of the support plate, forming first chamber 10. Support lands 36 provide extra mechanical support for the clear molded lumens surrounding the inlet and outlet channels 37 and 38 as they exit the sides of the support plate. To improve the appearance of the support plate 32, the surface is preferably textured. Land areas 39 and 40 may be defined by small ridges or grooves along their borders and a smooth surface finish within. Labels may be added to these land areas during clinical setup 13. MAR. 2002 17:02 SPRUSON FERGUSON 61 292615486 NO. 4733 P. 21 of the pressure transducer assembly to designate the specific measurement function and catheter being used with the invention, and/or to place product brand name labels.

From the drawing of Figure 3, it is easy' to see that: the transucer assembly according to the present invention can be used with the inlet and outlet channels 37 and 38 in either a horizontal or vertical position with the appropriate mounting brackets. For easy filling and dc-bubbling in the ICU or Operating Room, it is often preferred to place the fluid channels in the vertical position, as is more fully described in Figure 9. However, in the catheterization laboratory, where several transducers will Be .be d ais-chained together with interconnecting stopcocks located in between each transducer to accommodate connection and filling of multiple catheters. in a too 9manifold configuration, it is often more desirable to legato the inlet and outlet 7 :channels 37, 38 in the horizontal orientation. The invention is intended to accommodate both applications.

15Figure 4 is a top view of the first preferred embodiment, showing the threaded Is support bracket 32, a re-usable portion generally denoted by the numeral 2, rotating to. .0nut 24, ribs 20, cable jacket 25, insulated electrical conductors 26 29, vent tube rotating luer nut 33, outlet port 9, and hidden views of the clear molded portion 34 of toe dome and support land portion 36 of the support bracket.

As can be seen from this illustration, the molded support bracket 32 effectively provides a physical barrier between the clear molded portions of the disposable dome 7 and the re-usable portion 2. Any sterile tubing, catheter. or flush device components are intended to be installed to the disposable dome, with the molded support bracket serving as a sterile shield placed between such components and the re-usable portion 2. The lower extension of the threaded support bracket, as seen in this Figure as extending underneath the re-usable portion 2, is intended to be secured to an IV pole using a standard pate mount manifold clamp, as is well known in the art (for example, see Figure Once the transducer assembly I has been installed on an IV polusn a suitable clamping bracket attached to rcarmost portion of the threaded support bracket 32, the tubing, flushing, anid catheter components are assembled to the disposable dome portion 7, using sterile technique, without the need to touch the rcusable portion 2. The forward surface of the threaded support bracket 32 further 13. MAR. 2002 17:02 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 22 prevents inadvertent contact with the re-usable portion during manipulation of the sterile components being attached to the disposable dome portion 7.

In Figure 5 is shown an elevational croas-sectional view of a disposable dome portion 7 according to the present invention to illustrate the process of forming the isolating medium II. During manufacturing of the disposable dome portion 7, the clear molded portion 34 is ultrasonically welded, or solvent or adhesive bonded to the threaded support plate 32. A matingly formed dust cap 41 is inserted over the bottom end of the threaded support bracket 32 to prevent escape of fluid. The dust cap 41 ;.provides a convex shape of the gel in the opening in the threaded support plate *0 designed to be contacted by the diaphragm as earlier described. The lower portion of the container thus formed is filled with silicone gel in an uncured stae and the gel is cured in a contoured shape to form isolating gel I. The isolating gel I I is a pressure transmissive but electrically and biologically isolating media, such as a cross-linked !poly-dimethyl siloxane, for instance a platinum-cure, two part silicone gel available from Rhone-Poulenc as catalog N Visalox V-191. Once the gel is cured and with the dust cap in place, the disposable dome portion 7 is placed in a package and processed to produce a sterile packaged sub-part. When un-packaged for assembly by the medical practitioner onto the reusable portion, the dust cap is removed and discarded, *leaving a sterile, external convex surface of isolating medium II piesented to engage 20 with the re-usable portion, and more specifically to engage with diaphragm 12 or other contact surface such as in an embodiment from which the diaphragm has been deleted or integrally formed.

The dust cap 41 is preferably made of prosurc formable plastic material which will not adhere to curing silicone gel, such as polyethylene or plasticized PVC. The sides of the dust cap have groves designed to make an interference fit with the threads on the support plate. To provide an even tighter seal of the dust cap to the threaded support bracket 12. the dust cap can optionally be threaded on the portions contacting the threads of the support plate.

To further improve the mating of the diaphragm 12 to the isolating medium 11, the dust cap can be removed at any time after curing of the gel, and a drop of silicone oil applied to the center of the convex gel surface. This step can be performed, for 13. MAR. 2002 17:03 SPRUSON FERGUSON 51 292615485 NO. 4733 P. 23 -17instance, by briefly removing the dust cap alter curing but before packaging for sterilisation, applying the oil to the concave surf-ace formed in the dust cap, then reattaching the dust cap and resuming the packaging and sterilisation process as described above.

In Figure 6 is shown a further preferred embodiment 1 of the present invention in a cross-section view taken along the centerlines of fluid inlet and outlet ports 8 and 9. In this drawing, insulated electrical conductors 27 and 28 are not shown, but it shall be understood that they follow the same general direction, positioning, and course as the illustrated electrical conductors 26 and 29. Also, the rotating bier nuts 33, of the first io embodiment have been replaced with fixed luer receptacles which form an integral part of the clear molded dome portion 34. Any of a variety of conventional fluid line fasteners can be used, as will be apparent to those of skill in the adt.

*The embodiment of Fig. 6 operates in a similar manner to the first preferred embodiment, except that diaphragm 12 is now provided with a generally spherical shape is over it's active, pressure responding area. Further, more space has been provided in area 35 for placement of a thick film resistor calibrating network 42 for zero and span oooecompensation of a chip 4 which does not contain it's own on-ci hnfl compensation. In this embodiment, the thick-film network acts as a carrier for the chip.

o o The carrier is adhesively bonded to form the floor or second chamber 13. A pressure :o~ooe 2 transmitting media 15 fills the chamber and transmits hydraulic pressure signals from pressure responsive diaphragm 12 which is in communication with isolating medium 11I and the fluid in first chamber 10, to a first side of a silicon chip sensor 4. In this embodiment, the isolating medium 11 is preferably U-shaped, with the legs of the "U" pointing away from the fluid path and in the direction of the reusable portion of the transducer. Vent tube 30 provides an ambient pressure reference to the second side of the chip sensor. The thick-film network 42 is preferably attached to the re-usable portion 22 using an annular ring of silicone rubber 17. The sensor housing pins 31 are attached into sensor housing 22 and smaller soldered leads or wirebonds extend from said sensor housing pins to the thick film substrate or directly to the chip. Thus, placement of undue stresses from the cable and insulated electrical conductors 26-29 is avoided on the thick film substrate or chip. Alternately, insulated electrical conductors 26-29 can be of a sufficiently fine gauge that the electrical conductors Rt\L -P L1I664gpcjedockja 13. MAR. 2602 17:03 SPRUSON FERGUSON 61 292615486 NO. 4733 P. 24 can be soldered directly to the thick film substrate. Or, alternately. the pins can farm a spring contact to the thick film substrate 42, with the insulated electrical conductors in contact with insulation penetrating contacts which Caorn a part of the pin, see for instance US Patents 4,230,391 and 4,825,876 the disclosures of which are incorporated herein by reference. Such variations in electrical contact means shall be obvious those experienced in the art.

figure 7 is a front view of an embodiment of the disposable dome portion 7 according to the present invention, where a 3-way stopcock 43 and an auxiliary fluid 44 channel 44 have been added to the fluid outlet path 38 of the disposable dome portion 10 provide for convenient manipulation of sterile fluid volume or pressures at the auxiliary outlet port 45 for more convenient zeroing, calibrating. and blood drawing as shall be now described.

Disposable dome portion 7 is typically connected at it's inlet port 8 to a flush 2 device which is a controlled flow source of sterile saline. During setup, the flush device is used to fill the fluid inlet channel 37, the first chamber 10, the fluid outlet channel 38 and then ultimately the attached tubing and catheter, By inserting 3-way socc43in said fluid outlet channel several other fucton can beperformned.

Stopcock 43 is shown in it's normal pressure measuring position with the stopcock's :port in communication with the auxiliary channel 44 tured to the "off" or blocked position. In this position, normal fluid-fluid flow communications is allowed between the catheter and the first chamber 10. A continuous slow flow of sterile flush solution for the catheter is also supplied through the inlet port by the flush device. (in an alternate configuzation, a stopcock can be placed on the inlet port 8 and the flush device can placed in series with the pressure tubing leading fronm the outlet port 9 to the catheter.) When the stopcock "off indicator" on the handle is turned in the direction of the first chamber 10, pressure monitoring and flushing of the catheter is suspended, and sterile fluid in the catheter is in communication with auxiliary fluid channel 44 and auxiliary port 45. A syringe of approximately 10 CC capacity is attached to auxiliary port 45, typically with it's handle pushed fully down so that it's internal fluid volume is minimal. By pulling up on the: syringe handle, with the stopcock off arr0w 13, MAR. 2002 17:03 SPRUSON FERGUSON 61 292615486 NO. 4733 P. pointing toward the transducer, the medical practitioner can withdraw up to 10 CC'S of fluid from the catheter and interconnecting lines, thereby drawing blood up into the catheter and cubing for the "Ineedle-less" collection of blood at a HEMOLOC TM Bile 52 just proximal to the catheter (see Figure After collection of a small blood sample at the HEMOLOC TM site, all of the remaining blood in the catheter and tube can be injected back into the patient by pushing down on the handle of the syrige.

This needle- les and non -blood-spill sampling technique thus is a great advantage for reducing the risk of infection to medical personnel from inadvertent needle ("sticks") i.e. wounds to practitioners, or blood spillage in the vicinity of the patient.

Further, if the stopcock handle is turned such that the off indicator on it's handle is turned in the direction of the outlet pant 9, then pressure monitoring and *t flushing of the catheter is suspended and the auxiliary fluid channel and syringe can be filled with sterile saline wing the flush device, for instance for use 'in t th4rmiltiULUn cardiac output injections. And by tempararily removing the syringe with the stopcock handle in this position, the fluid int chamber 10 and thus the silicon chip sensor is exposed to an atmospheric or other reference pressure for zeroing or calibrating the pressure measurement systern. Whent the auxiliary port is used for zeroing of the transducer according to the above-described method, the medical practitioner typically would locate the vertical level of the auxiliary port 45 at the mnid- *20 beant height for the most accurate calibration or the pressure measurement system to the patient's current position and posture.

Thus, addition of the stopcock 43, auxiliary fluid channel 44, and auxiliary port offers distinct advantages of an easy and an accurate method of calibrating the pressure measurement system, plus an improved method of drawing blood samples for laboratory analysis while not wasting or spilling any of the patient's blood.

Figure 8 shows an isometric view of the pants comprising yet a third preferred embodiment of the inlvention. In this embodiment, the support plate 36 is made part of the re-usable portion 2. The re-usable portion is assembled by first bonding the sensor housing 23 into a recessed area surrounded by a raised rim on the back side of the support plate 56. The second chamber portion of the sensor housing with it's raised rim and diaphragm passes through a hole in the support plate so that these 13. MAR. 2002 17:04 SPRUSON FERGUSON 61 292615485 NO. 4733 P. 26 leadihg portions are disposed on the front side of the plate in alignment wit a mtn hole 59 in clear molded Portion 34.

Insulated electrical conductors 26-29 are soldered to sensor housing pins 31, and routed through a channel in the support plowe to an external electrical cable 25 After the support plate, sensor housing, and insulated electrical conductw:: ate assembled, the recessed area in the back of the support plate is preferably potted with RTV silicone rubber or epoxy to eliminate leaks and shorts, while keeping all sealant away from vent hole 67 so that it remains exposed to ambient air pressure,

A

clamping ring 63 is then placed over raised rim 60 in a loosely fitting arrangement so 10 that it can rotate around the sensor housing center ais. The clamping ring contains ramps on it's inside walls which arc designed to be matingly engaged with the barbs; :57 on the disposable portion when the barbs are inserted into muating holes 61 and the ring is rotated clockwise, Thus the clamping ring and barbs are an engagement and :retention means to draw together and hold the re-usable and disposable portions when IS operated as described above.

Self-adhesive label 66 is then attached to rim 64 on the clamping ring, and reusable bracket 22 is then bonded to a horizontal grove in the support plate to complete the assembly of the re-usable portion.

The mating hole 59, surrounded by raised sealing edge 6713s formed in a rear portion of said first chamber in the back of the clear molded portion 34 and the rearward convex portion of the isolatig medium 11I can be seen in the mating bole 59. The clear molded dome portion, generally denoted by the numeral 34, includes two barbs 57, and three raised pads 58, As explained above the barbs form a mating and engagement means with the re-usable portion. During engagement, the raised pads 58 provide a slight displacement of the upper and bottom portions of sterile shield portion 68 away from the support plate 21. As a result, when the re-usable portions are drawn together by the engagement mechanism of the barbs 57 and clamping ring 63, a slight bending of the two mating pieces at their horizontal centers will produce a first contact in the region of hole 59 and sealing edge 67, thus assuring a firm arid repeatable seal of the hydraulic pressure signal transfer path.

13. MAR. 2062 17:04 SPRUSON FERGUSON 61 292615486 NO. 4733 P. 27 The sterile shield 68 prevents the medical practitioner frm touching there usable portion when manipulating the zeroing stopcock or when Inspecting the Seethrough portion of' the dome. For cost reasons, it is intended to be constructed of thin plastics such a s polyoarbonate, and is preferably molded in a single step molding process during the same step where the inlet and outlet fluid channels, and clear molded portion is formed.

This third preferred embodiment has an advantage over the fit two preferred embdimntsforthe minimization of plastic material wed in the disposable portion.

This feature may be of particular advantage in markets where there are restrictions and :10 high costs for hospitals and suppliers associated with excessive use of throw away plastics materials.

x: Figure 9 shows an isometric view of one form of complete pressue measurement system for monitoring arid maintenance of a single catheter according to the. present invention, including a source of pressurized flush solution 46 which 154 includes a plastic IV bag filled with solution, a pressure cuft inflation bulb, and pressue gauge, an IV administration set 47 incorporating a drip chamber, a flush device 48 connected to inlet port 8 of transducer assembly 1, a 10 CC disposable syringe 49 incorporating a sterile protection boat over it's barrel and handle which is I connected to auxiliary port 45, insulated electrical conductors in the cable 920 connecting to an electrical interface connector 54, said interface connector being in electrical communication with a pressure measurement and display systemn 55, a manifold pole mount clamp 50 attached to an IV pole and mechanically clamping a rear portion of the transducer asembly I in a groove in said clamp using clamp screws, a pressure tubing connecting the outlet port 9 to a HEMQLOC TM port 52, and said HEMOLOC TM being connected to a fluid tubing leading to the catheter 53 adapted for measuiring a physiological pressure of interest in a living body.

With reference to figure 10, there is illustrated a perspective view of a fouMt embodiment of the present invention. As shown, the fourth embodiment of the pressure transducer assembly I includes an inlet fluid port 8 and an outlet fluid port 9. This embodiment of the pressure transducer assembly I is worn by fastening bands such as velcro, straps 68 around a patient's forearm. Preferably, the patient wears the 13. MAR. 2002 17:04 SPRUSON FERGUSON 61 2 92615486 NO., 4733 P. 28 pressure transducer I in the wrist vicinity, such as in the position in which a wristwatch is normally worn.

With reference to Figures 11, 11A and IIB, there is illustrated a cross-sectional view of the fourth embodiment of th pressure transducer assembly 1. This particular embodiment utilizes a "snap-fit" mating between the disposable dome 7 and the reusable portion 2 in accordance with the present invention. In addition to the advantages of previous embodiments, this configuration preferably minimizes the amount of sterile plastic materials that must be discarded after each patient application of the pressure transducer assembly I. Furthermore, this configuration of the fourth 0@* 10 embodiment minimizes both patient and staff biocontamination risks.

Figures I1I and IA illustrat the reusable portion 2 and the disposable dome S"7 in an assembled state, specifically where the disposable dome 7 is snap-fitted to the reusable portion 2. The disposable dome 7 includes a smooth walled, and preferably ~substantially straight through fluid filling path and central fluid chamber 10, The fluid chamber O10 communicates with and is preferably defined in part by a surface of the biological isolating medium 11. One side of the isolating medium 1 I is in pressure transmitting contact with a diaphragm 12, and sealed against said diaphragm by annular sealing edge 67. Isolating medium 11 may be composed of approximately mil thick 70 Durometer medical grade silicone rubber. Desirably, silicone appears to provide adequate rupture resistance to prevent breaching of the sterile barrier and contamination or escape of the catheter fluid when the dome is removed from the transducer base 2. A silicone"0-ring structure 90 is preferably formed on the outer edge of medium 11 to provide a secure mounting means for the diaphragm. Medium 11 thus forms a part of disposable dome portion 7 and is in pressure transmitting contact with pressure transmitting medium 15, which contains an integral diaphragm 12 at its contacting surface, as previously described.

Alternatively, as shown in Figure Il B, the medium I I including 0-ring may be secured by a holding and retaining structure 91. To further improve the smoothness of the fluid path to avoid trapping air bubbles, the isolating medium 11 may include a small amnount of silicone gel which may be dripped upon and cured on top of a preformed diaphragm which is made from silicon rubber as described above, -22- 13. MAR. 2002 17:04 SPRUSON FERGUSON 61 2 92615486 NO, 4733 P. 29 Preferably, the gel 73 will advantageously form inside of all of the sharp corners around the outer diameter of the preformed diaphragm where it contacts the disposable dome 7, thus providing an extremely smooth and essentially straight through interior fluid path, while providing additional electrical biological isolation of the catheter fluid.

Being responsive to the hydraulic signal as presented by medium 11, a 10 mil thick diaphragm 12 made from nitrile rubber conv.eys -the.hydraulic pressure signal into the second chamber 13. and then via pressure transmitting media 15 to the sensor chip 4. In the embodiment of Figure lIB, the cross sectional area of the chamber 13 10 adjacent the diaphragm 12 is greater than the cross sectional area of the chamber 13 adjacent the chip 4. The pressure transmitting media 15 may comprise silicone gel.

The chip 4 is attached to the floor o[ the second chamber 13 by a silicon chip carrier 42, such as a thick-film network, and a silicone adhesive sealant 17. Wire bond leads carry the pressure signal from the chip 4 to a cable 25, and ultimately to an electrical interface connector 54 (Figure 10). The sensor vent tube 30 conveys an atmospheric reference pressure to one side of pressure sensor chip 4 via vent hole 16.

Sensor vent tube 30 is vented on its proximal end at connector 54 (See Figure 12), and at it's distal end it connects to vent hole 16 as it exits the back side of thick film substrate 42.

20 A particular advantage of this embodiment is that the transducer disposable portion 7 is quickJy and easily attached and detached from the reusable portion 2 using snap-on attachment structures 74. The attachment structures 74 preferably consist of one or more and preferably two compressible barbs 76 which are premolded into opposite sides of the disposable dome 7. A set of receiving tabs 78 are formed in the reusable portion 2. The barbs 76 are configured to mate with tabs 78 in order to removably secure the disposable dome 7 to the reusable portion 2. The user grasps and compresses the barbs 76 at locations 69 while pulling upward in order to release the disposable dome 7 from the reusable portion 2. To reafch the dome 7, the user simply pushes the dome 7 onto the reusable portion so that the barbs 76 engage with the tabs 78 and thereby lock the dome 7 in place.

13. MAR. 2002 17:05 SPRUSON FERGUSON 61 292615486 NO. 4733 P. In general, the snap interftt stnucture between the reusable portion 2 and the disposable dome 7 ca be based upon an interference fit. ratchet type structure, friction fit or other depending upon the desired product characteristics. in a typical product, at learn one interference surface 92 connected to or on the dome 7 releasbly engages at least one corresponding surface attached to or on the reusable portion 2.

In the embodiment illustrated in Figure 11, the interference surface 92 appears on the barb 16 engaged with the complementary surface on tab 78. The interference surface 92 is connected to the dame 7 by way of a flexible arn 94 which preferably biases 10 the interference surface 92 in the direction of the complementary surface on reusable 10 portion 2. Thus, overcoming the bias created by the ann 94 permits the interference surface 92 to extend through an aperture 86 on the reusable portion 2. Releasing the compression force permits the bias in the arm 94 to engage interference surface 92 with the corresponding surface on the reusable portion 2. Although a single two part locking structure having the foregoing characteristics can be used, preferably two opposing locking structures as illustrated in Figure I I will be used to securely mount the two components of the pressure transducer together.

0 Any of at variety of alternate releasble snap-fit type structures can be used as will be apparent to those of skill in the art, as Long as the structur selected provides 0 a sufficient Compression to produce an adequate propagation of the pressure signal across the interface between medias' I and In the embodiment of Figure 11, the biological isolating medium I I anid the diaphragm 12 arc both preferably made from soft elastomeric material with their thickest vertica cross sections located along their outer peripheries. The two protrusions 67 compress the two elastomeric materials as the disposable dome 7 is advanced against the reusable portion 2. The resulting compression between the protrusions 67 and the elastomeric materials preferably provides a spring force to hold the engagement surface 92 on barbs 76 firmly engaged against the complementary surface on tabs 78 of the reusable portion. This snap-type fit thus holds the disposable dome 7 firmly attacd to the reusable portion 2 with sufficient spring force to provide excellent hydraulic signal transmission between the two parts. The orientation or the tWO elaStomeric materials with their thicker outermost retaining sections -24- 13. MAR. 2002 17:05 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 31 extending away from the fluid path, provides the special benefit of an essentially straight through fluid path through the disposable dome 7 which is unique in the field of disposable domes for a reusable transducer. Heretofore, disposable domes for reusable transducers have been designed with their isolating mediums diaphragms) thickest vertical retaining portion facing upward from the pressure transmitting surface, thus necessitating a crooked or stepped flow path through the dome, which often results in the undesirable entrapment of bubbles. Thus, the novel shape of isolating medium I1 in the various embodiments of the invention as herein described provides special benefits for ease of use comparable to fully disposable transducer designs.

Figure 12 illustrates a perspective view of the fourth embodiment of the pressure transducer 1, where the reusable portion 2 and disposable dome 7 are disassembled from one another. As shown, a sterile sheath S0 has tubular shape and •is preferably made from thin polyethylene or other plastic flexible tubing. The sterile S "15 sheath 80 houses the cable 25 and electrical connector 54 during use. Certain portions of the snap-fit pressure transducer structure, including the disposable dome 7, the "velcro strap and the sheath 80 are preferably supplied sterile and made to completely shroud the reusable portion 2 of the transducer I when assembled. In 4 clinical use, the reusable portion 2 may be cleaned but need not necessarily be sterile.

Thus, this embodiment is intended for direct mounting of the transducer assembly 1 to the patient, as may be often be advantageous when transporting the patient, or when the physician desires to reduce the catheter and tubing length to obtain higher fidelity pressure recordings. As illustrated in Figure 11, the velcto strap 68 is used to securely attach the transducer assembly 1 to the patient's wrist or forearm during such use, by threading the strap ends through the outer slots in the reusable housing 2, and thence around the patient's forearm or other appendage.

Figures 13A and 13B illustrate an adaptor accessory 82 that may be used to mount one or more of the fourth embodiment of the present invention to an IV pole manifold holder assembly. As shown in Figure 13B, a plurality of accessory barbs 84 extend outward from the adaptor accesory 12. The accessory barbs 84 are preferably arranged in sets of two and are configured to mate with apertures 86 in the 13. MAR. 2002 17:05 SPRIJSON FERGUSON 61 292615486 NO. 4733 P. 32 reusable portion 2 of the transducer assembly 1. This allows the reusable portion 2 to be removably mounted to an IV pole or ozher convenient support structure through the adaptor accessory 82 in a snap-fit manner, Hence, the fourth embodiment of the invention may be quickly removed from the patient and mounted to an IV pole manifold holder assembly using the adapter accessory 82 shown in Figurs 13A and 13B.

This option may be of particular advantage when the patient reaches an, intensive care ward, where it is desired to put the transducer in a more fixed location goesadjacent to the monitoring equipment. To use this accessory, the velcro straps 68 located at the patient's wrist are disconnected and the transducer assembly I is removed front the patient's arm. During this procedure, sterile technique is preferably maintained and the transducer preferably continues to monitor the patient blood pressure sigals. The velcro strap 68 is then pulled from the back of the transducer seesassembly 1, and the remaining pieces of the transducer assembly, namely the reusable :2>15 portion 2, assembled to disposable dome 7, is snapped into a waiting adapter accessory 82, which has been pro-attached to an IV pole manifold holder 50, such as the type as illustrated in Figure 9.

Thus, the embodiment as shown in Figures 10-13 facilitates easy configurability to a variety of clinical situations based on the snap-together feature of the present invention. The present invention also provides economic savings for the hospital since the reusable portion 2 of the transducer assembly I may be easily reused by the clinical staff without resort to expensive re-sterilizatiion techniques. The cost of manufacturing the single use sterile materials that are discarded after each application is also considerably lower than the cost of manufacture of a fully disposable, single-use transducer with integral sensor chip.

While the present invention has been disclosed with respect to the preferred embodiments thereof, those of ordinary skill in the art will understand that further modifications to the invention may be made within the moape of the claims that follow hereinibelow. Accordingly, it is not intended that the scope of the invention be limited to what has been disclosed above buit, instead, should be determined entirely by reference to the claims that follow.

Claims (2)

13. MAR. 2602 17:06 SPRUSON FERGUSON 61 292615486 NO. 4733 P. 33 -27- The claims defining the invention are as follows- 1. A disposable dome for use in combination with a reusable sensor to form a reusable transducer assembly for measuring pressure in a fluid line coupled to a catheter inserted into a living body for making direct pressure measurements in areas within the body of medical interest, said disposable dome including a fastener arranged to releasably engage a complementary surface on the reusable sensor and discardable after a single use, said dome including an electrically and biologically isolating coupling media shaped in conjwnction with the dome to form a straight through fluid filling path, and wherein said media transmits hydraulic pressure signals ftom a fluid-filled chamber in to said dome to the reusable sensor. S2. The apparatus according to claim 1 wherein the coupling media comprises one or more elastomers in an interior cavity of the disposable dome, the elastomer fon-ning a smooth internal path for the flow of fluid.

0683. The apparatus according to claim 2 wherein the elastomer is at least in part a silicone gel. The apparatus according to claim 2 wherein the elastomer is cast, cured, or formed in place within the disposable dome to form. a convex pressure transmitting surface prior to assembly onto the reusable sensor. The apparatus of claim 1 wherein said isolating medium is U-shaped, with the legs of the pointing away from the fluid path and in the direction of the reusable sensor of the transducer. 06. The apparatus of claim 1 wherein said fastener consists of a snap together retaining mechanism which can be disengaged by pressing on the sides of the dome. 7. The apparatus according to claim 1, said assembly comprising: a housing; an inlet and an outlet port in the housing, having a fluid flow path extending therebetween; a cavity in the flow path, said cavity divided into a first and a second chambers by a flexible diaphragmn; said flow path in communication with said catheter and said first chamber within said housing; said first chamber further containing said isolating media; [LALIfJI]! IJd64qe-dadacAk 13. MAR. 2602 17:06 SPRUSON FERGUSON 61 292615486 NO. 4733 P. 34 -28- said second chamber containing a compensated pressure sensor spaced from said diaphragm with one side of said pressure sensor sealingly disposed in communication with a vent hole in a surface of said chamber, said vent hale providing an ambient air pressure reference to a first side of the pressure sensor; s pressure transmissive media in said second chamber for transmitting hydraulic pressure signals from said diaphragm to a second side of the pressure sensor; and an electrical conductor connected to the pressure sensor and extending from said housing. 8. The apparatus of claim 7, wherein the housing comprises first and second removably securable components with a first component containing the first chamber and said inlet and outlet ports adapted to be removable and disposable after a single use. 9. The apparatus of claim 7, wherein the outlet port is in fluid communication with an integral stopcock having an auxiliary port for zeroing and/or catheter fluid volume manipulation. 410. The apparatus of claim 7, wherein the flexible diaphragm comprises a membrane selected from the group consisting of polyisoprene, mylar, polyamide, stainless steel alloy, high density polyethylene, silicone rubber, and nitrile or butyl rubber. *11. The apparatus of claim 7, wherein the isolating media and the pressure 0*2o transmissive media comprise dissimilar materials at their contacting surfaces, such that S the isolating media and the pressure transmissive when placed in intimate sealing contact do not adhere to one another. 12. The apparatus of claim 7, wherein the diaphragm comprises a surface of the pressure transrnissive media in the second chamber. 13. The apparatus of claim 12 wherein said diaphragm is formed by curing a first type of silicone elastomer, and then curing a second elastomer in contact with the first. 14. A disposable dome for use in combination with a reusable sensor to form a reusable transducer assembly for measuring pressure in a fluid line coupled to a catheter inserted into a living body for making direct pressure measurements in areas within the body of medical interest, said disposable dome portion including a fastener arranged to releasably engage a complementary surface on the reusable sensor and discardable after a single use, said dome including an electrically and biologically isolating coupling media shaped in conjunction with the dome, said assembly comprising (RA LMLLjI106 spoccvch 13. MAR. 2062 17:06 SPRUSON FERGUSON 61 292615486 NO. 4733 P. 9 @9 9 9 9 99 99 9 -29- a housing, an inlet and an outlet port in the housing, having a fluid flow path extending therebetween, and a cavity in the flow path, said cavity being divided into a first chamber and a second chamber by a flexible diaphragm, wherein said coupling media is disposed adjacent to said diaphragm to transmit hydraulic pressure signals from said first chamber to said second chamber via said diaphragm, said coupling media not comprising a diaphragm, and comprising one or more elastomers, which form a smooth internal path for the flow of fluid. The apparatus according to claim 14, wherein said coupling media comprises a gel. 16. A method of monitoring a physiologic pressure, comprising the steps of: providing a patient having a catheter in communication with a fluid-carrying vessel within the patient; providing a one time use disposable dome having a housing, a straight flow path through the housing and a hydraulic pressure signal transmitting media disposed in the 15 housing between the flow path and a pressure signal transmitting surface exposed to the outside of the housing, said dome having at least a first snap fit engagement surface thereon; providing a pressure transducer having a pressure signal receiving surface, and at least a second snap fit engagement surface; removably placing the first snap fit engagement surface in interlocking contact with the second snap fit engagement surface, thereby retaining the pressure signal transmitting surface in pressure signal transmitting contact with the pressure signal receiving surface; placing the flow path in fluid communication with the patient by way of the catheter; and monitoring the physiological pressure detected by the transducer. 17. A method of monitoring a physiologic pressure as mn Claim 16, further comprising the steps of moving the first snap fit engagement surface out of contact with the second snap fit engagement surface, and removing the one time use disposable dome from the pressure transducer. 18. A method of making a disposable dome for a reusable transducer, said disposable dome having an essentially straight through flow path produced by constructing an isolating media consisting of at least a preformed diaphragm wherein the diaphragm has an outer mounting and retaining ring structure that is thicker in the vertical IAMLJI 1664wRci9.docakah 13. MAR. 2002 17:06 SPRUSON FERGUSON 61 2 92615486 NO. 4733 P. 36 dimension than the thickness of the diaphragm's center portion, and wherein the retaining ring structure is displaced in the direction of the resusable transducer, and wherein the counter opposed surface in contact with the disposable dome if flat or alternatively shaped to form a smooth internal flow path. 19. A disposable dome, substantially as herein described with reference to any one of the embodiments of the invention shown in the accompanying drawings. A method of monitoring a physiologic pressure said method being substantially as herein described with reference to any one of the embodiments of the invention shown in the accompanying drawings. 21. A method of making a disposable dome, substantially as herein :described with reference to any one of the embodiments of the invention shown in the accompanying drawings. Dated 13 March, 2002 Sunscope International, Inc. Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON c o •o [k \LmLL) 116640tlcdoe:keb