Abstract:
The present invention presents various novel approaches to solving the problems inherent in measuring biological pressures in high pressure systems. Thus, to protect a pressure transducer exposed to fluid flows at higher pressures than its overpressure rating, a novel valve is used that closes a protected leg in which the transducer is located. The various exemplary embodiments of such valves each have a high pressure input, one or more low pressure inputs, and an output. In operation, when a high pressure fluid flow occurs at a high pressure input, such valves automatically close the low pressure inputs. Alternatively, a novel transducer system is presented, which automatically limits the effective pressure sensed by a transducer to a certain maximum.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 11/401,695, filed on Apr. 10, 2006, now U.S. Pat. No. 7,617,837, which is a continuation application of Ser. No. 10/316,147, filed on Dec. 9, 2002, now U.S. Pat. No. 7,389,788, which claims the benefit of U.S. Provisional Patent Application Ser. Nos. 60/338,859 and 60/338,883, each filed on Dec. 7, 2001, all of which are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the field of biomedical technology and, in particular, to methods, systems and apparatus for protecting biological pressure measurement devices in high fluid pressure environments. 
     BACKGROUND OF THE INVENTION 
     Certain medical procedures, such as, for example, contrast media injections during cardiological procedures, can require that liquids (such as radiographic contrast agents in, for example, angiography) be injected into a patient&#39;s system under high pressures. Such pressures are commonly as high as 1200 lb/in 2  (psi) or more than 60,000 mm Hg. While performing such procedures it is also desirable to measure the patient&#39;s biological pressures. For example, in angiography it is desirable to record the much lower intravascular and intracardiac pressures—generally falling within the range of −1 to +6 psi—between high pressure injections of the contrast media. Generally, pressure transducers that are designed for physiological measurements cannot tolerate even moderate injection pressures and therefore must be isolated from the fluid path during a high-pressure injection. One such method of isolating pressure transducers is described in U.S. Pat. No. 5,800,397 (Wilson et al.), that uses a manifold to isolate a low pressure system line—where a pressure transducer can be located—from a high pressure contrast medium injection line based on a spool valve concept. 
     Spool-type manifolds are common in industrial applications and can manage very high pressures. However, such manifolds also require close manufacturing tolerances, are generally expensive, and are designed for use in permanent installations. Also, due to its mechanical “stickiness”, the position (open/closed) of a spool-type manifold needs to be monitored by a sensor to avoid malfunction with insipation of blood during a syringe refill. In medical applications, plastic and elastomeric parts are commonly used. This is because pressures are generally low in such environments and sterile parts need to be inexpensive so that for hygienic and safety reasons they can be readily disposed of after a single use. Such polymers have a drawback; they are less conducive to a consistent fit between different parts, which tends to decrease reliability. No device currently exists that combines low cost and ease of manufacture and use with the high pressure capability of industrial valves. 
     In addition, devices adapted to measure high pressures which would, by definition, be capable of withstanding those pressures, are simply not sensitive enough to accurately measure physiological pressures. Thus, in the example discussed above, a physician performing an angiography using only a high-pressure sensor could, in fact, monitor the injection pressure while contrast material is being injected, but would have no way of monitoring the patient&#39;s blood pressure when no injection is occurring. Thus, what is needed in the art is a method of facilitating the deployment of pressure measuring devices—that is sensitive enough to measure physiological pressures—within high fluid pressure environments in a manner that either isolates or protects such devices when high pressures are present. 
     Thus, within the objects of the present invention are methods, apparatus and systems which facilitate placing devices that make accurate physiological pressure measurements within environments that are intermittently subjected to high pressure fluid flow. 
     SUMMARY OF THE INVENTION 
     The present invention presents various novel approaches to solving the problems inherent in measuring biological pressures in high pressure systems. To protect a pressure transducer exposed to fluid flows at higher pressures than its overpressure rating, a novel valve is used that closes a protected leg in which the transducer is located. The various exemplary embodiments of such valves each have a high pressure input, one or more low pressure inputs, and an output. In operation, when a high pressure fluid flow occurs at a high pressure input, the valve automatically closes the low pressure inputs. Alternatively, a novel transducer system is presented, which automatically limits the effective pressure sensed by a transducer to a certain maximum. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an expanded view of an exemplary valve assembly according the present invention; 
         FIG. 2  is a cross sectional view taken along a direction normal to fluid flow of the exemplary valve assembly of  FIG. 1  depicting the normal (low pressure) mode of operation; 
         FIG. 3  is a cross sectional view taken along a direction normal to fluid flow of the exemplary valve assembly of  FIG. 1  depicting the open (high pressure) mode of operation; 
         FIG. 4  is a frontal view of the exemplary valve assembly of  FIG. 1 ; 
         FIG. 5  is a perspective view of an exemplary valve body according to the present invention showing the saline and output ports; 
         FIG. 6  is a side view of the exemplary valve body of  FIG. 5 ; 
         FIG. 7  is a cross section taken at the position A-A of the exemplary valve body of  FIG. 6 ; 
         FIG. 8  is a detail drawing of the indicated portion (B) of  FIG. 7 ; 
         FIGS. 9(   a )-( c ) illustrate an exemplary disc holder according to the present invention; 
         FIGS. 9(   d ) and  9 ( e ) illustrate an exemplary valve disc according to the present invention; 
         FIG. 10  depicts an exemplary rotary valve manifold according to the present invention in the normal mode; 
         FIG. 11  depicts the exemplary rotary valve manifold of  FIG. 10  in the open mode; 
         FIGS. 12(   a ) and  12 ( b ) depict an alternative exemplary rotary valve manifold according to the present invention in the normal and open modes, respectively; 
         FIG. 13  depicts an exemplary plunger manifold valve according to the present invention in the normal mode; 
         FIG. 14  depicts the exemplary plunger manifold valve of  FIG. 12  in the open mode; 
         FIGS. 15(   a )- 15 ( c ) depict open, normal, and assembly views, respectively, of an alternate embodiment of the exemplary disc valve of  FIGS. 1-9  according to the present invention; 
         FIGS. 16(   a )- 16 ( d ) depict exemplary relative dimensionalities of a valve body for the exemplary disc valve of  FIG. 15 ; 
         FIGS. 17(   a )- 17 ( b ) depict exemplary relative dimensionalities of a valve disc for the exemplary disc valve of  FIG. 15 ; 
         FIGS. 18(   a )- 18 ( d ) depict exemplary relative dimensionalities of a disc holder for the exemplary disc valve of  FIG. 15 ; 
         FIG. 19  depicts an exemplary 3D rendering of the exemplary disc valve of  FIG. 15 ; 
         FIGS. 20(   a ) and  20 ( b ) depict the normal and open views, respectively of an exemplary sleeve shuttle valve according to the present invention; 
         FIGS. 21(   a ) and  21 ( b ) depict an exemplary bidirectional elastomeric valve according to the present invention; 
         FIG. 22  depicts an exemplary transducer with barrier apparatus according to the present invention; 
         FIG. 23  depicts a non-disposable portion of the exemplary transducer of  FIG. 22 ; 
         FIG. 24  depicts a disposable portion of the exemplary transducer of  FIG. 22 ; 
         FIGS. 25-26  depict an alternative exemplary transducer with barrier apparatus according to the present invention; 
         FIGS. 27(   a )- 27 ( c ) depict an exemplary embodiment of an automatic shuttle valve with manual override; and 
         FIGS. 28(   a )- 28 ( c ) depict an exemplary disc valve according to the present invention with a built-in seat for a low pressure transducer. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Disc Valve Embodiment 
     It is within the objects of the present invention to provide a valve that is inexpensive, reliable, biocompatible, non-allergenic and able to withstand pressures up to 1500 psi. Moreover, the valve must be able to withstand several modes of sterilization (gamma irradiation, ethylene oxide and e-beam) as well as have a clear housing. It must be easy to remove all bubbles when it is flushed with saline or contrast. The pressure gradients required in the valve are complex. It must have a reliable cracking pressure above 9 psi and, upon opening, ensure that an attached pressure gauge (generally, but not always, located in the saline port, as described below) is never exposed to pressures above approximately 15 psi (1 atm). To achieve this, because generally a pressure sensing connection is very ‘stiff’, parts of the valve must not project or bulge into the sensing path even at very high pressure conditions. Finally, the components of the valve must not degrade the fidelity of a physiologic pressure signal. 
     In addition to pressure measurement from a tube system through which a high pressure injection is performed, it is often desirable to infuse fluids, such as physiological saline, into a patient through the same tubing system through which the high pressure injection is made. The valve described herein allows a continuous fluid path to a low pressure infusion reservoir to tubing connected eventually to the patient&#39;s blood vessel. Injection from another fluid reservoir will passively close off the low pressure reservoir system, preventing back flow from the high pressure reservoir to the low pressure reservoir. 
     With reference to  FIG. 1 , an exemplary embodiment of a high-pressure activated valve will be described. An exemplary low and high-pressure elastomeric valve is comprised of a disc holder  101 , a middle valve disc  102  and a valve body  103 . The valve body  103  and disc holder  102  are made of a relatively rigid polymer, such as for example, polycarbonate, and the valve disc  102  is molded of an elastomer, preferably silicone rubber, with a slit in the center. 
     The elastomeric disc  102  with the slit is sandwiched between the valve body  103  and disc holder  101  and is affixed at the perimeter of the disc. Such affixation may be effected by, for example, entrapment, adhesion, mechanical or chemical welding, or any other means known in the art. The valve body  103  and disc holder  101  are bonded together, by, for example, sonic welding, UV curable adhesive, mechanical threads or snap (interference) locking, or other bonding or adhesion technologies as may be known in the art, thus entrapping the disc. 
     In an exemplary embodiment, the valve has at least two, and preferably three, ports that communicate with attached tubing. Such ports are, for example, (a) a contrast inlet port, (b) a saline inlet and pressure transducer port, and (c) a patient or outlet port. In an exemplary embodiment the disc holder  101  contains such a contrast inlet port, as is shown in more detail in  FIG. 2 , described next. 
     With reference to  FIG. 2 , a valve body  203  contains a saline/transducer  220  and a patient/outlet  221  port. Also, a disc holder inlet port hole  222  is tapered outward (in the forward flow direction, i.e., from right to left in  FIG. 2 ) to create a pocket  240  in front of an elastomeric disc  202  so that as fluid travels through the hole  222  and into the empty pocket, air is forced from the pocket (purged) through the disc slit  241  and into the valve body  203  (more precisely, into the cavity in the valve body which is adapted to fluid flow). Thus, for example, in an angiographic procedure as described above, as contrast media fills the empty pocket  240  of the disc holder  201  and pressure thus builds, the elastomeric valve disc  202  bends and eventually opens the slit  241  (which occurs at a certain pressure, known and referred to herein as the ‘cracking pressure’) to inject fluid into the valve body. The dimensions of the pocket allow for control of the cracking pressure; at a given pressure, exposing a greater surface of the disc to that pressure will increase the force upon a disc and thus lower the cracking pressure. The situation where the slit opens and fluid flows from the inlet port  222  through the slit into the valve body  203  is shown in more detail in  FIG. 3 , described below. 
     Continuing with reference to  FIG. 2 , in an exemplary embodiment a valve body  203  has two internal tapers. A narrow taper  205  closest to the disc  202  that contains the saline port, and a second wider taper  206 . In operation, the narrow taper next to the disc  202  allows the saline/transducer port  220  to be sealed as pressure builds up and before fluid passes through the disc  202 . The second, wider taper  206  and associated cavity create room for the disc to expand and allow the slit  241  to open fully. The converging angles (in the forward flow direction) also promote flushing of air from the valve so that no bubbles are left behind. 
       FIG. 3  depicts the exemplary valve of  FIG. 2  in the high pressure fluid flow state described above. With reference to  FIG. 3  contrast fluid under high pressure flows through inlet port  322 . This has caused the pressure applied to the right side of the disc  302  to exceed the ‘cracking pressure’, which caused disc  302  to expand in the direction of flow (or to the left in  FIG. 3 ), opening the disc slit  341 . As the disc expanded it covered the opening of the saline/transducer port  320  in the cavity of the valve body  303 . At the same time, the force maintained on the disc  302  by the incoming fluid keeps the saline port shut during high pressure fluid flow, such as, for example, is experienced in a contrast fluid injection. The first taper has, for example, a ring-shaped channel  350  where the saline port  320  is located, thus allowing the interior of the valve body  303  to be completely filled with saline during initial setup. In an exemplary embodiment, the rest of the valve body  303  and the corners of the channel are preferably rounded to eliminate any trapping of air bubbles during setup and. Also, such a channel helps air to be removed by a vacuum applied manually using a syringe. 
     In exemplary embodiments, the valve can be used in connection with low pressure (60 psi) to high pressure (1200 psi) medical fluid injections. It can also be used with CT, MRI and cardiology contrast media injection systems. Additionally, a two-port version of the valve with the elimination of the saline/transducer port  320  can be manufactured economically enough to act as a check valve. Such a high/low pressure valve is thus inexpensive to manufacture, having a simple design and consisting of three molded parts that can be assembled and bonded together with ease. 
     The disc holder contains the fluid inlet port and, in exemplary embodiments, can be molded or machined out of, for example, polycarbonate, PET, acrylic or any other tough polymer as may be known in the art that can withstand pressures up to 1500 psi. In exemplary embodiments of the invention the elastomeric disc  202 ,  302  is preferably circular and may be, for example, molded or cut from sheet silicone rubber or other elastomers including, for example, polyurethane and latex. In preferred exemplary embodiments, properties of an elastomeric disc material are, for example, a durometer in the range of 40-70 A, more specifically, for example, 55 A, a tensile strength of 1000-1500 psi, an elongation of 300-700%, and a tear strength 150-300 lbs./inch. In a preferred exemplary embodiment the disc may be 0.060″ thick or may have a range of 0.020″ to 0.200″ in thickness depending on the durometer, fluid and slit dimensions. In an exemplary embodiment the slit in the middle of the disc is preferably 0.125″ long, and may be 0.050″-0.30″ in length. In preferred exemplary embodiments the disc has a preferred working surface diameter of 0.580″ and may range from 0.250″ to 2.00″. 
     The valve body  203 ,  303  is molded or machined out of, for example, polycarbonate, PET, acrylic or other tough polymers that can withstand high pressures up to 1500 psi. In exemplary embodiments it contains the fluid outlet port  221 ,  321  and the saline inlet/transducer port  220 ,  320 . In exemplary embodiments the internal shape of the valve body has two tapers  205 ,  206 , the first taper being at an angle from the vertical (i.e., from a plane that is normal to the fluid flow direction, and substantially parallel to the plane the disc surface is in when the disc is non-distended as in  FIG. 2 ) of, for example, 10°-45°, and in a preferred exemplary embodiment 200, with a width of, for example, 0.020″-0.500″, and in a preferred exemplary embodiment 0.115″. In exemplary embodiments the saline inlet/transducer port  220 ,  320  is located in the first taper so that the taper enables the disc  202 ,  302  to close the saline port  220 ,  320  when fluid flows from the injection system. In exemplary embodiments the second taper may be at an angle upward from the vertical (as above), for example, 45°-90° and preferably 0.161″ deep (depth being measured along the direction of fluid flow) to create space for the disc to expand and the slit  241 ,  341  to open for passage of fluid through the disc. 
     In exemplary embodiments the valve is assembled by placing a disc  202 ,  302  in the valve body  203 ,  303 . Then the disc holder  201 ,  301  is placed into the valve body  203 ,  303  and the two parts are, for example, pressed together mechanically or threaded together and either UV-bonded, sonic welded or attached by any equivalent means as may be known in the art. The disc is thus trapped between the valve body and the disc holder all along the disc&#39;s outer edge to prevent leaks. In exemplary embodiments the three fluid ports may have, for example, male or female luer threads to conveniently attach to the injection system, patient catheter and saline/transducer system. 
     Thus, the disc valve of the current invention accommodates both high and low pressure fluid systems. Also more than one port can be provided in the valve body  203 ,  303 , and can thus be closed or opened during injection, e.g. up to 4 saline-type ports and can be used for different purposes, such as drug injection, patient fluid sampling and a separate pressure transducer. For example, during a high or low pressure injection (although high enough to exceed the cracking pressure) all such ports can be simultaneously closed, and when the injection system is OFF all such ports will be open, or “ON” and can be used simultaneously or as required. 
       FIG. 4  is a head-on view looking into the contrast fluid output port against the direction of fluid flow. With reference to  FIG. 4 , besides the contrast fluid output port  421 , there can be seen the channel  450 , which is an annular ring whose center is the center of the contrast fluid output port and which is positioned relatively close to the edge of the valve disc (unseen in  FIG. 4 ). As was described in connection with  FIG. 3 , within the channel  450  is the one or more saline/pressure transducer ports  420 . 
       FIG. 5  is a perspective view of the valve body ( 103  with respect to  FIG. 1 ) showing the contrast fluid output port  521 , as well as a saline port  520 . It is understood that numerous saline ports could be placed anywhere within the channel ( 450  with respect to  FIG. 4 ;  350  with respect to  FIG. 3 ) as shall be described below. 
       FIG. 6  is a side view of the valve body  103  and in the exemplary embodiment depicted in  FIG. 6  are shown some representative exemplary dimensions. The overall diameter of the valve body  601  is shown to be one unit, the diameter of the contrast fluid output port  621  is shown to be 0.3 units, overall depth  660  (measured herein along the direction of fluid flow) is shown to be 0.700 units, and the depth of the non-tapered portion of the valve body  661  as 0.35 units. It is understood that the dimensions in  FIG. 6  are merely exemplary, and thus show an example of a relationship between the various dimensions of this apparatus. Numerous other dimensions and relationships therebetween are possible and may in fact be desirable, depending on the context and properties of the device that are desired to be accentuated or diminished. For example, the depth of the tapered region  662  is one parameter that controls the cracking pressure. The more room there is in a cavity on the side of the valve disc, the easier it is for the valve disc to be pushed forward (there being less resistance provided by air in a cavity than other possible components), and the lower the cracking pressure. Thus, there is an inverse proportional relationship between the depth  662  and the cracking pressure (“CP”). The greater the area through which a given pressure acts on the disc, the greater the force acting on the disc. Thus CP=k/depth, for some unit determined constant k. 
       FIG. 7  depicts a cross-section along the line A-A of the exemplary valve body depicted in  FIG. 6 . With reference to  FIG. 7 , a number of exemplary design dimensions are displayed, such as the inside diameter of the contrast medium output port  701 ; the outside diameter of that output port  702 ; the diameter of the cavity at the front edge where the cavity connects into the contrast fluid output port  703 ; the diameter at the beginning of the second tapered region in the valve body cavity  704 ; the diameter at the beginning of the first tapered region in the valve body cavity  705 ; and the inside diameter of the valve body in the non-tapered region  706 , which is the diameter into which a given valve disc will fit. As described above, so as not to have any liquid leakage, the diameter of an exemplary disc designed to fit within the diameter  706  will have that same diameter to ensure a tight fit. Exemplary dimensions of  701 - 706  are, respectively, 0.149, 0.169, 0.210, 0.350, 0.580 and 0.830 units. It is also possible to make the diameter of the disc slightly larger in alternative exemplary embodiments, thus ensuring a tight fit, where liquids of very low viscosity are used which require a greater attention to leakage prevention. 
     It is noted that for the exemplary embodiment depicted in  FIG. 7 , an exemplary valve disc designed to fit therein is depicted in  FIG. 9(   d ) in horizontal top view and in  FIG. 9(   e ) in a vertical side view showing. With reference to  FIG. 9(   d ) it can be seen that the diameter of the depicted exemplary valve disc is 0.83 units, identical to the dimension depicted in  FIG. 7  element  706 . As can be seen with reference to  FIG. 7 , there is a region  750  depicted as being surrounded by a circle labeled “B.” This region is depicted in  FIG. 8 , as shall next be described. 
       FIG. 8  depicts the detailed B region in a scale magnified by a factor of 6 relative to  FIG. 7 . The area of detail depicted in  FIG. 8  is, as should be obvious to the reader, the exemplary saline port within the valve body. With reference to  FIG. 8 , it can be seen that angle  807 , representing the angle of the outer taper of the valve body is, in this exemplary embodiment, 60° off of the vertical and that the distance from the corner where the outer tapered region begins in the outer surface of the valve body to the center of the saline port is, in this exemplary embodiment, 0.192 units  801 . Also, angle  802 , which represents the angle of the inner taper or the first taper  205  (with reference to  FIG. 2 ) is shown to be 30° in this exemplary embodiment. The exemplary diameter of the saline port  810  is 0.169 units. As well, with reference to  FIG. 8 ,  803  indicates channel depth to manually purge air from the transducer side of the system (which does not require if it is auto purged),  804  a width of an indent to clamp a valve disc positively,  805  a location of an indent to clamp a valve disc positively, and  806  a height of an indent for clamping a disc. In this exemplary embodiment,  803 - 806  are, respectively, 0.025, 0.013, 0.050, and 0.015 units. 
     With reference to  FIGS. 9(   a ) through  9 ( c ), there are depicted various views of the disc holder  101  (with reference to  FIG. 1)  in the following exemplary dimensionalities. With reference to  FIG. 9(   a ), an exemplary outward diameter  901  is 0.83 units. It is noted that this dimension corresponds to element  706  in  FIG. 7 , which is precisely the exemplary dimension into which the inner diameter of the non-tapered portion of the valve body into which the disc holder is to fit. As well, index numbers  902 - 905  represent exemplary inner diameters of the depicted exemplary disc holder, which are 0.810, 0.785, 0.652 and 0.600 units, respectively. With reference to  FIG. 9(   b ),  906  shows an exemplary height of a main portion of an exemplary disc holder, 0.300 units, and  907  an exemplary height of the high pressure input port, 0.250 units. With reference to  FIG. 9(   c ),  910  shows an exemplary diameter of a main portion of an exemplary disc holder,  911  an exemplary outer diameter of the high pressure input port,  912  an exemplary inner diameter thereof,  914  an exemplary port size for creating sufficient pressure,  915  an exemplary pocket size for creating pressure, and  908  an exemplary pocket angle of 82° (from the vertical) for an exemplary pocket, and  913  an exemplary height of a protrusion for clamping within the indent shown in  FIG. 8 . In this exemplary embodiment,  910 - 915  are, respectively, 0.810, 0.300, 0.169, 0.015, 0.149 and 0.200 units. 
     With reference to  FIGS. 9(   d ) and  9 ( e ), views of and exemplary dimensions for an exemplary valve disc are shown. With reference to  FIG. 9(   d ), as discussed above, an exemplary outer diameter of the valve disc is shown as 0.83 units. The exemplary disc slit length  930  is shown as 0.15 units. It is noted that given the relationship between the disc length and the diameter of the valve disc, even when the valve disc slit is completely open, there is no concern for leakage at the perimeter of the valve disc. Thus, one or more additional saline ports could be placed anywhere within the annular ring identified as the channel  350  with respect to  FIG. 3 , which would identically and simultaneously be closed upon the currents of the configuration of the valve depicted in  FIG. 3 . With respect to  FIG. 9(   e ),  940  the thickness of the valve disc is shown and an exemplary thickness of the valve disc shown here in this exemplary embodiment having 0.06 units of thickness. 
     The design parameters are used to set a cracking pressure for the valve. In general cracking pressure is a function of disc thickness, slit length, durometer of the elastomeric disc and the primary taper of the valve body. Cracking pressure increases with increasing disc thickness and disc material durometer, and cracking pressure decreases with decreasing slit length of the disc and primary taper of the valve body. 
     Rotary Valve Manifold Embodiment 
     In an alternative exemplary embodiment, a rotary valve apparatus is utilized to switch between the high pressure and low pressure environments.  FIG. 10  depicts an exemplary rotary valve embodiment according to the present invention. With reference to  FIG. 10 , an exemplary rotary valve is a three-piece design, comprising an outer housing  1050  and an inner rotating seal  1051 . In preferred exemplary embodiments the three pieces should be molded using, for example, polycarbonate, or as a specific example, Makrolon Rx-2530. In an exemplary embodiment the internal rotating seal is preferably molded using TPE.  FIG. 10  shows the valve in a static state. There is a path from the saline port  1020  through the center of the TPE seal  1051  to the patient output port  1021 , but there is no open fluid path to the patient output port  1021  from the contrast media port  1022 . 
       FIG. 11  depicts the situation where the valve is open for contrast media. When contrast media is injected at port  1122 , fluid dynamics puts more pressure on the front of the seal cavity  1151 ( a ), thus rotating the disc counterclockwise approximately 25 degrees (this angular measure being a function of the angular arc that the inner seal must travel before a fluid path between contrast and patient is established, itself a function of the device geometries) before pressure equalizes in the chamber as a result of an open path for the contrast media through the patient output port  1121 . Thus, this rotation of the inner seal closes the saline fluid path and opens a contrast media to patient fluid path. In addition, the rotation of the inner seal stores energy in the twist or torsion in the member  1160  which protrudes from the inner seal to hold the inner seal  1151  in the housing  1150 . Such member is, in the depicted exemplary embodiment, a 3D rectangular structure whose cross section is a square whose centroid is the axis of rotation of the inner seal  1151 , but such member can be any of a variety of shapes as may be known in the art. When pressure drops at the contrast media connection, the seal rotates back to the static state, closing the contrast media port  1122  and opening the saline path  1120 . 
       FIGS. 12(   a ) and  12 ( b ) respectively depict an alternative exemplary embodiment of the rotary valve of  FIGS. 10-11 . As indicated in  FIG. 12(   a ), this exemplary embodiment utilizes an additional protrusion  1251  of the valve housing  1210  into the central rotary seal area creating an air gap  1250  that is compressed when the valve goes into the open state as depicted in  FIG. 12(   b ), thus storing potential energy in the compression of the air in the air gap  1250 . This air gap assists the rotary seal to return to the normal state of  FIG. 12(   a ) when there is no longer any high pressure flow entering the contrast input port  1222  and exiting the outlet port  1221 , as the compressed air exerts a net torque (directed into the plane of the drawing) on the rotary seal which is no longer balanced by any torque resulting from the high pressure flow. In alternative exemplary embodiments, the air gap could be replaced by a more compressible material relative to the rotary seal, or the air gap could be contained within the rotary seal without being exposed to the housing. 
     Plunger Valve Embodiment 
     With reference to  FIGS. 13 and 14 , an alternative exemplary embodiment of the invention is next discussed. These Figures depict the normal and open states, respectively, of an exemplary plunger valve. This design uses a minimum of parts (three in the depicted exemplary embodiment). With reference to  FIG. 13 , the normal state is depicted, including the saline inlet port  1320 , contrast inlet port,  1322 , and outlet port  1321 . The manifold body  1350 ,  1450  and end cap  1360  can be molded using, for example, a polycarbonate such as, for example, Makrolon Rx-2530. The internal plunger  1351  with diaphragm  1361 ,  1461  may be molded using, for example, a 70 durometer EPDM, polyisoprene or equivalent material as may be known in the art. 
       FIG. 14  shows the valve in a normal or static state. The path for saline  1420  is open and saline flows around the internal plunger  1451  by means of indentations  1470  caused by a reduced diameter of the plunger  1451  at its central portion.  FIG. 14  shows the valve open for contrast media. When the valve sees pressure on the contrast connection  1422  the internal plunger  1451  is pushed back (rightward in the diagram) towards the end cap inside face  1452  and the diaphragm  1461  stretches back (creating potential energy). This closes the saline fluid path  1420  and opens the contrast media to patient fluid path. When pressure drops at the contrast media connection  1422  the stretched diaphragm  1461  pushes the plunger  1451  back to the normal state, as depicted in  FIG. 13 . This closes the contrast media port  1422  and opens the saline path  1420 ,  1421 . 
     Alternate Disc Valve Embodiment 
     In connection with  FIGS. 15   a  through  15   c , an alternative embodiment of the disc valve will be next described.  FIGS. 15(   a ),  15 ( b ) and  15 ( c ) are alternative exemplary embodiments of the disc valve, and correspond respectively to  FIGS. 3 ,  2  and  1 , showing a variant of the exemplary disc valve depicted in those Figs. Hence, merely the differences between the exemplary embodiment of  FIGS. 1-3  and the exemplary embodiment of  FIGS. 15(   a ) through  15 ( c ) will be noted. With reference to  FIG. 15(   a ), there is a contrast fluid input port  1522 , an output port  1521 , and a saline input port  1520 . As can be seen with reference to  FIG. 15(   a ), there are the same components in this exemplary embodiment as there were in the exemplary embodiment presented above, i.e., a disc holder, a valve body, and a valve disc. What is notable about the exemplary embodiment of  FIGS. 15(   a ) through  15 ( c ) is the shape of the cavity within the valve body  1503 , as well as the differences in the shape of the taper where the contrast fluid input port  1522  contacts the valve disc  1502 . A comparison of  FIGS. 2 and 3  with  FIGS. 15(   b ) and  15 ( a ), respectively, shows that the cavity within the valve body  1503  in the exemplary embodiment depicted in  FIG. 15(   a ) is significantly larger than that of  FIG. 3 . Further, it has more the shape of a rectangle with rounded corners, rather than a trapezoid, such as is created by the first and second tapers, with reference to  FIGS. 2 and 3 . This results in a lower cracking pressure, inasmuch as there is less resistance to the forward movement of the valve disc  1502  than there is in the exemplary embodiment depicted in  FIGS. 3 and 2 , respectively. Also, one can see that the saline input port  1520  in  FIG. 15  is placed on the top, as opposed to having them placed on the bottom as in  FIGS. 2 and 3 . As described above, one or many saline ports can be provided within the channel and their placement is arbitrary and will, in general, be a function of the design context. 
     With reference to  FIG. 15(   c ) and by comparison with  FIG. 1 , it can be seen that there is some change in the exemplary embodiment depicted in  FIG. 15(   c ) relative to that of  FIG. 1  as concerns the valve disc  1502 ,  102 . In  FIG. 15(   c ) the valve disc  1502  is not purely flat but has a lip on the rearward or topward in the diagram side.  FIGS. 16(   a ) through  16 ( d ),  17 ( a ) through  17 ( b ) and  18 ( a ) through  18 ( d ) provide exemplary relative dimensions of various components of the disc valve of  FIGS. 15   a  through  15   c .  FIG. 16  collectively provide exemplary relative dimensions for the internal profile of the exemplary valve body. Exemplary dimensions in such exemplary valve body design which are useful in controlling performance are, for example, inner cavity length 0.180  1680 , inner cavity height 0.400  1681 , output port diameter 0.149  1682  and 20° taper  1685 . Such parameters are used to achieve desirable shutting of the saline/transducer port and maintain balanced fluid dynamics. 
       FIG. 17  collectively provide exemplary dimensionalities for the valve disc according to this alternative exemplary embodiment. It is noted that  FIG. 17(   b ) depicts a cross-section along the line A-A in  FIG. 17(   a ) across a diameter of the entire disc, and in the depicted orientation the slit runs vertically and is depicted as  1710  in  FIG. 17(   b ). Further, with reference to  FIG. 17(   b ), one can see the lip structure of this exemplary embodiment of the valve disc as discussed above. 
     The exemplary disc design of  FIG. 17(   b ) having a bulge on one side in the middle helps in bending the disc to close a saline/transducer port quickly. Also, this exemplary feature increases cracking pressure and prevents the disc from inverting due to any increase in back pressure. In alternative exemplary embodiments the slit in the disc  1710  may have a taper, i.e., be at an angle with the horizontal, which can increase cracking pressure by 25% and also help prevent inversion of the disc due to any increased back pressure. 
     Accordingly, the disc holder, as shown in  FIG. 18 , includes a 21° taper from the exemplary dimensions of 0.450 to 0.149 to accommodate the bulge in the disc in order to increase the cracking pressure and prevent inversion of the disc. 
     Finally,  FIGS. 18(   a ) through  18 ( d ) give exemplary relative dimensions of the disc holder  1501  in  FIG. 15(   c ). As above, these relative dimensions are merely exemplary and numerous other dimensions could be utilized changing some or all of the dimension relationships depicted in  FIGS. 16 through 18  collectively, as may be implemented by one skilled in the art. 
       FIG. 19  is a 3D rendering of the components of the disc valve of  FIGS. 15 through 18  showing the three components, the valve body  1903 , showing the saline port  1920  provided within it, the valve disc  1902  and the disc holder  1901 . 
     Spool Valve Embodiment 
     What will next be described, with reference to  FIG. 20 , is an exemplary spool valve embodiment according to the present invention.  FIG. 20(   a ) depicts the valve in the open position and  FIG. 20(   b ) depicts the valve in the closed position. With reference to  FIG. 20(   a ), there is a saline port  2020 , a output port that goes to the patient  2021 , and a contrast medium or high pressure input port  2022 . There is provided as well a spring  2050  which exerts pressure on a spool  2051 , which is a cylinder with a hollowed-out center which is accessed from the high pressure port  2022  via an orifice  2052 . When there is no high pressure on the back circular plane of the spool  2051 , the spring  2050  holds it in such manner that the saline port  2020  has a fluid pathway to the patient output port  2021 . This is the situation depicted in  FIG. 20(   a ). With reference to  FIG. 20(   b ), the situation is depicted where there is high pressure fluid flow entering the valve through the high pressure input port  2022 , which exerts pressure on the back cylindrical plane  2060  of the spool and pushes it against the spring  2050  such that it moves to the left in the diagram or in the direction of fluid flow, occluding the opening of the saline port  2022 , thus protecting it. Therefore, if a low pressure, high-sensitivity transducer can be placed within the protective saline port  2020  such that it can measure the pressure of fluid, and therefore the pressure in the patient when there is no high pressure flow, and when there is high pressure fluid flow at the high pressure input port  2022 , the protected leg and therefore the transducer within it are cut off from the fluid flow and the high pressure of the high pressure fluid flow is not exerted on the low-pressure transducer. 
     Bi-Directional Disc Valve 
     With reference to  FIGS. 21(   a ) and  21 ( b ), an additional exemplary embodiment of the disc valve is depicted. As can be seen from  FIG. 21(   b ), this is a bi-directional high pressure elastomeric valve. Port  1   2121  and Port  3   2123  could either be used as an input or an output for high pressure fluid flow. In the exemplary embodiment depicted in  FIG. 21(   b ), the valve disc  2102  is similar to the valve disc used in the prior exemplary unidirectional embodiments discussed, however the shapes of the disc holder  2101  and the valve body  2103  have changed somewhat to become more similar. This is because in order for the flow to be bi-directional there needs to be a cavity on both sides of the valve disc. Thus the two cavities tend to look similar. While saline ports can be provided on both sides, they can only be protected from high pressure flow when the saline port that is used is on the output side of the high pressure flow. For example, with reference to  FIG. 21(   b ), the depicted saline Port  2   2120  can only be protected if Port  1   2121  is the input and Port  3   2123  is the output. Although the exemplary embodiment depicted in  FIG. 21(   b ) shows an identical angle of displacement of the valve disc under high pressure flow, i.e., 30° off of the vertical in each direction, it is not necessary that these angles be identical, and designers will use variations in the sizes of the cavities on either side of the valve disc as well as the angle of full distention of the valve disc to vary the cracking pressure in each of the forward and backward directions. There are many exemplary uses which such a bi-directional high pressure elastomer valve would have, among them, for example, are using it in the forward direction as the unidirectional valve described above, and then also using it as a high pressure check valve, such that back flow is allowed at a certain high pressure which exceeds the cracking pressure in the backward direction. 
     It is thus understood that the bi-directional high pressure elastomeric valve depicted in  FIGS. 21(   a ) and  21 ( b ) will have many uses beyond simply protecting low-pressure transducers or low-pressure systems from high pressure flow in angiographic procedures. 
     Enhanced HP Transducer (No Valve Protection Required) 
     Within the objects of the present invention are methods and systems to protect low-pressure systems (such as, for example, those containing low-pressure and high sensitivity, but low over-pressure rated transducers) from high pressure flow. Thus far what has been described are various exemplary embodiments of the valves which are designed to do that. The other side of the coin, however, is to design a transducer with additional apparatus that will protect it from the pressures exerted by high pressure fluid flow, even if it is exposed to such high pressure fluid flow. What is next described with reference to  FIGS. 22 through 26  are transducer designs that do just that. Using the transducers, the exemplary embodiments of which are depicted in  FIGS. 22 through 26 , there is no need to put the transducer in a protected low-pressure line, such as, for example, the saline port as described above in the valve embodiments. Rather, the transducer can be placed within a high pressure line. When high pressure fluid flow is present in the line the transducer will be exposed to that high pressure, but a barrier apparatus will protect the transducer such that the pressure exerted against it is held at certain maximum which is below the overpressure rating for the transducer. When there is low pressure in the line the transducer is free to operate in its full dynamic range and measure, according to its high sensitivity, various intercardiac, intravenous, or interstitial pressures as may be desirous to be measured in a given patient. 
     With reference to  FIG. 22 , there is provided a transducer  2201  within a transducer housing  2202  and a transducer contact  2203  which impacts upon the transducer  2201  pressing against the impact plane  2205  of the transducer. The transducer contact  2203  is moved ultimately by the membrane contact  2210  which is within a high pressure tubing  2250  and exposed to any high pressure fluid flow, as indicated by the arrow  2290  at the bottom right of the tubing. The fluid pressure is exerted on the transducer contact  2203  via a pressure transmission rod  2204  which is connected to the plane of a membrane  2220  via a membrane contact  2210 . Thus, the pressure transmission rod, the membrane contact, the transducer contact and the transducer, are all insulated from actual contact with the fluid for hygienic purposes. The only part having contact with the actual fluid is the membrane  2220 . The fluid is not allowed to enter into the transducer housing  2202  by operation of the seal ring  2291 , which provides a means to insert the transducer housing into the high pressure tubing but seal it off from any fluid communication therewith. 
     As can be seen with reference to  FIG. 22 , a fluid flow in the high pressure tubing will exert pressure on the membrane  2220 , which will transmit it to the membrane contact  2210  and by means of a pressure transmission rod  2204  transfer the resultant force to the transducer contact  2203 . The transducer contact  2203  will then be pushed in the upward direction, exerting a pressure on the transducer  2201 . However, the transducer contact is limited as to how much pressure it can exert against a transducer by means of the transducer contact limiter  2251 , which is a ring around the outward perimeter or circumference of the transducer, which serves to stop the transducer contact from any further upward vertical motion. The transducer contact limiter is comprised of any rigid material as may be known in the art. Although it may not be absolutely rigid the transducer contact limiter will have a spring constant which is significantly more rigid than that of the transducer. Thus, in relative terms the transducer contact limiter provides much more rigid resistance to the upward motion of the transducer contact than does the transducer itself. This allows the transducer to measure any pressure between zero and a certain maximum which is governed by the stopping effect that the transducer contact limiter has on the upward motion of the transducer contact. This maximum pressure which can be measured by the transducer will, of course, be set below its overpressure rating by a significant safety margin, as may be chosen by a given designer according to criteria as may be known in the art. In an exemplary embodiment such safety margin will be 20%. 
     Such a configuration allows the transducer to measure a wide range of pressures in a very sensitive manner within the biological or physiological regime, such as, for example, pressures normally occurring in patients to which the high pressure tubing is connected; however, when there is high pressure flow within the high pressure tubing  2250 , such as in angiographic procedures as described above, the pressure reading by the transducer will be capped at the maximum pressure. 
     Also shown in  FIG. 22  is ECG contact  2280 , the functionality of which is explained in detail below with reference to  FIGS. 25 and 26 . 
       FIG. 23  illustrates the portion of the transducer depicted in  FIG. 22  which does not contact the fluid and is a non-disposable multi-use apparatus. 
       FIG. 24  depicts the disposable portion of the transducer assembly depicted in  FIG. 22 , being the membrane  2420 , the seal ring  2491 , and a stainless steel tube  2492 . It is within the hollow of the stainless steel tube that the transducer contact and the transmission rod move up or down, as determined by the pressure exerted against the membrane. As can be seen in the exemplary embodiment of the membrane depicted in  FIG. 24 , it can withstand pressures up to 1500 psi, which means that it is impervious to fluid flow up to those pressures. 
       FIGS. 25 and 26  depict an alternative exemplary embodiment of the high pressure transducer. In this embodiment the transducer probe (being the pressure transmission rod in the membrane contact, as depicted in  FIG. 22 ), does not extend downward into the high pressure tubing, but measure pressures at the tubing layer itself. This is done by screwing on the transducer housing as opposed to inserting it within the cavity of the high pressure tubing. The functionality of the alternative exemplary embodiment is equivalent, the only differences between the two exemplary embodiments being the mechanism of insertion or affixation of the transducer, pressure transmission rod, and membrane contact to the high pressure tubing in such manner that it can reliably measure pressures. In the second exemplary embodiment since there is no protrusion into the volume of the tubing, there is no need for the metallic tube  2492  of  FIG. 24 . Thus, the ECG contact needs a conductive pathway to the fluid in the tube. This is provided by the ECG metal lead  2581 , to which the circular ECG Contact  2580  connects. 
     The ECG contact is utilized in the following manner. During medical procedures, catheters are often inserted into the vasculature to measure pressure, withdraw blood or inject contrast media or other substances. In such instances the lumen of the catheter tubing is generally filled with a conductive liquid, such as, for example, saline, blood or radiographic contrast media. 
     During certain medical procedures such as, for example, angiography, it is also often desirable to obtain an electrocardiographic measurement of the heart&#39;s electrical activity. Such a measurement is usually obtained, for example, from electrodes applied to the patient&#39;s skin or from electrodes mounted on the outside of catheters. A minimum of two electrocardiographic electrode attachments to the patient are generally required and the voltage potential between the electrodes (either singly or in groups) is recorded over time. These measurements allow monitoring of the patient&#39;s condition as well as diagnosis of specific heart abnormalities, such as, for example, such as lack of blood flow. 
     In the exemplary embodiment depicted in  FIGS. 25 and 26 , the electrocardiographic (ECG) electrodes from the heart can be obtained through the conductive fluid in the lumen of the catheter in the patient. The other (return path) electrode, or combination of electrodes, can be obtained from surface electrodes attached to the patient&#39;s skin or from electrodes attached to the side of the catheter within the patient. Alternatively, two electrode leads could be obtained from the lumens of a catheter with two or more lumens filled with a conductive substance. 
     The sensing of at least one ECG electrode from the catheter lumen would allow easier ECG measurements for patients undergoing such medical procedures because it would simplify or eliminate the need for skin electrodes. It would also allow a recording of the intravascular ECG, which may have diagnostic importance or be useful for other purposes as may be known in the art. 
     Shuttle Valve with Manual Override 
       FIG. 27(   a ) through  27 ( c ) depict an exemplary embodiment of a shuttle valve with manual override. In general, in the exemplary embodiments of valves discussed so far, there have been two position/three way valves, which direct either saline or contrast to a single port connected to the patient. In such systems, it is further required to have a three position/three way stopcock distal from the valve to aspirate fluid from and administer fluid to the same patient connection. This increases cost and complexity. The exemplary embodiment shuttle valve depicted in  FIG. 27  merges these two functions in one valve by adding an additional sample/aspiration port  2723 , as shall next be described. The exemplary embodiment of  FIG. 27  also allows existing two position/three way valves to be located at the extreme distal end of a disposable set, which may in fact increase the accuracy and fidelity of biological pressure waveforms by substituting a lumen filled with contrast with one filled with less viscous saline. Moreover, a push-button style valve is generally easier to actuate than a similar rotary style valve. 
     In an exemplary embodiment of the shuttle valve shown in  FIG. 27 , the ports are configured in parallel. This facilitates the use of a side-by-side dual lumen tube. With reference to  FIG. 27(   a ), there is depicted the normal state of the valve where the saline port  2720  has an open fluid communication pathway with the patient output port  2721 . This figure also depicts the contrast port  2722  as described above, and an additional port unique to this embodiment which is the sample/aspiration port  2723 . With reference to  FIG. 27(   b ), the shuttle has moved rightward within the figure, according to the following process. The spring on the left, shown with the larger windings,  2750  has a higher spring constant. The spring on the right  2751  has a lower spring constant. In normal operation as depicted in  FIG. 27(   a ), the spring with lower force constant biases the shuttle  2750  against the spring with the higher force constant. During an injection, however, fluid pressure from the flow into the contrast port  2722  shifts the shuttle against the spring with the lower force constant  2751  closing up the saline port  2720  to the patient port  2721  and opening the contrast port  2722  to the patient port  2721 . Once the injection is complete, the low force constant spring  2751  once again biases the shuttle toward the high force constant spring  2750 , thus reopening the connection between the patient  2721  and saline  2720  ports while closing the connection between the contrast  2722  and patient  2721  ports. 
     Additionally, according to the exemplary embodiment depicted in  FIG. 27(   a ), when desired the shuttle may be manually biased further towards the high force constant spring  2750  which opens a connection between the sample aspiration port  2723  and the patient port  2721  by means of a bypass connection  2760  from bypass inlet  2761  to bypass outlet  2762  between the patient  2721  and sample  2723  ports. This situation is depicted in  FIG. 27(   c ). This opening of a connection between the sample/aspiration  2723  and patient  2721  ports closes the other two ports, namely the contrast port  2722  and the saline port  2720 . Such a configuration allows for a sample aspiration, blood aspiration, or the administration of medications. The manual biasing of spring  2750  can be implemented and released via a push button, or such other device as may be known in the art. 
       FIGS. 28(   a ) through  29 ( c ) depict an alternate exemplary embodiment of a disc valve. In this exemplary embodiment, location for a transducer is provided within the valve body itself. With reference to  FIG. 28(   a ), there is provided an output port  2821 , a saline port  2820 , and a transducer lead port  2890 , through which electric leads running out of a transducer can be run.  FIG. 28(   b ) depicts a cross section of  FIG. 28(   a ), depicting a high pressure input  2822 , an output port  2821 , a saline port  2820 , and an exemplary location for a transducer  2891 . Both the saline port and the transducer at location  2891  are sealed off from any high pressure flow by disc member  2802 , here shown in the normal position.  FIG. 28(   c ) depicts the disc in the open position, as when high pressure flow enters via high pressure input port  2822 . 
     The present invention has been described in connection with exemplary embodiments and exemplary preferred embodiments and implementations, as examples only. It will be understood by those having ordinary skill in the pertinent art that modifications to any of the embodiments or preferred embodiments may be easily made without materially departing from the scope and spirit of the present invention as defined by the appended claims.