WO1993013818A1

WO1993013818A1 - Dual-diameter multifunction catheter

Info

Publication number: WO1993013818A1
Application number: PCT/US1992/000415
Authority: WO
Inventors: Dipankar Ganguly; Faina Pulvermakher
Original assignee: Diagnostic Devices Group, Limited
Priority date: 1990-03-15
Filing date: 1992-01-16
Publication date: 1993-07-22
Also published as: US5354220A; US5286259A; US5108369A

Abstract

A catheter (10) is disclosed having a stepped coaxial construction formed by an internal tube (12) and an external tube (14). The internal tube includes a distal pressure lumen (26), a balloon inflation lumen (28), and a sensor lumen (30). The external tube includes the first proximal pressure lumen (48), second proximal pressure lumen (50), injection lumen (52), and transducer lead lumen (54). A cylindrical transducer (16), sensor (18), and balloon (42) are supported on the internal and external tubes, which allow the transducer to be coaxially mounted thereon. The catheter has a high lumen count, large lumen cross-sectional area, is easy to construct and use, and allows cardiac output to be measured continuously, without sacrificing other currently available catheter functions.

Description

DUAL-DIAMETER MULTIFUNCTION CATHETER

Field of the Invention This invention relates generally to catheters and, more particularly, catheters having a dual-diameter construction. Background of the Invention

Catheters have long been used in the medical field to invasively obt patient information and administer treatment. A conventional catheter is elongate tube having a distal end and a proximal end. The distal end is desig for insertion into a fluid-filled passageway or cavity in the patient, such as on the various intravascular conduits. The proximal end of the catheter rem outside of the patient and is provided with a termination assembly accessible the health care provider. In this manner, the catheter provides a communicat link between the patient's fluid-filled passageway or cavity and the health c provider for diagnosis and treatment. Typically, the catheter includes one or more axial conduits known as lum extending between the distal and proximal ends of the catheter. These lum may contain, for example, electrical wires or optical fibers that transmit infor tion between sensors located at the distal end of the catheter and bedside inst ments at the proximal end of the catheter. The operation of the sensors controlled and their outputs interpreted by the bedside instruments, allowing sensor/catheter/instrument system to be used for monitoring and diagnosis.

Other lumens may extend between the termination assembly and po provided at various points along the catheter, placing the termination assembly the catheter in fluid communication with those ports. As a result, characterist of fluids in the patient passageway can be monitored and additional therapeu luids can be introduced by the health care provider.

One application in which catheters have been extensively used is the det mination of volumetric flow rate in an intravascular conduit. In that rega several catheter-based techniques have been developed to determine a patien cardiac output, i.e., the volumetric flow rate of blood in the patient's pulmona artery.

The first of these approaches is conventionally termed the "thermal dilutio method. Under this approach, a bolus of cold solution is introduced into one several lumens in a multiple-lumen catheter, via the termination assembly. T cold solution then enters the intravascular conduit through a port at the end of t lumen and on the exterior of the catheter. A thermistor located on the dist downstream end of the catheter is coupled to the termination assembly by wir positioned in another lumen. The "dilution" of, or change in, blood temperature the thermistor with time is then measured by an instrument coupled to the ter nation assembly. The resultant thermal change is electronically interpreted a cardiac output computed therefrom.

Thermal dilution techniques also typically employ an inflatable segment balloon at the distal end of the catheter. This balloon is coupled to the termin tion assembly by yet another lumen in the catheter. The balloon can, thus, controllably inflated by the health care provider and used as a flotation device f acilitate positioning of the catheter in the pulmonary artery.

The thermal dilution method does, however, have certain disadvantages. F example, this technique has proved to be of limited accuracy. In addition, cu bersome apparatus are required to provide the bolus and only intermittent info mation can be obtained.

Another approach to the measurement of cardiac output involves the use ultrasonic energy. Unlike the thermal dilution method discussed above, ultrason techniques can provide cardiac output measurements continuously. This is considerable value in the treatment of critically ill patients whose cardiac fun tions may change abruptly.

Ultrasonic techniques involve the use of a transducer positioned close to t distal end of the catheter. This transducer is connected to the terminatio assembly at the proximal end of the catheter by electrical wires threaded throu one of the catheter lumens. A bedside monitor attached to the terminatio assembly applies a high-frequency electrical signal (typically in the megaHert range) to the transducer, causing it to emit ultrasonic energy. Some of th emitted ultrasonic energy is then reflected by the blood cells flowing past th catheter and returned to the transducer.. This reflected and returned energy shi ted in frequency in accordance with the Doppler phenomenon. . The transducer converts the Doppler-shifted, returned ultrasonic energy an output electrical signal. This output electrical signal is then received by bedside monitor via the lumen wiring and is used to quantitatively detect amplitude and frequency-shifted Doppler signal associated with the ultraso energy re lected from the moving blood cells.

Existing ultrasonic measurement systems process the amplitude and f quency shift information electronically to estimate the average velocity of blood flowing through the conduit in which the transducer-carrying catheter inserted. Such systems also require that an independent estimation of the cro sectional area of the conduit be made using one of a variety of techniques tau in the literature, including, for example, the approach disclosed in U.S. Pat No. 4,802,490. Cardiac output is then computed by multiplying the average vel ity and cross-sectional area estimates.

One particular method of generating and processing ultrasonic signals for in cardiac output determination employs a cylindrical transducer. The transdu is mounted coaxially on a catheter suitable for insertion into the pulmon artery. As will be appreciated, there is, thus, a need for a catheter capable carrying a cylindrical ultrasound transducer. Furthermore, in order to enha the clinical utility of such a catheter, the catheter should retain some or all of clinical functions already available through nonultrasonic catheters. Such multifunction catheter would, however, be subject to a variety of design c straints.

Specifically, the catheter must have a small diameter for insertion into t particular conduit of interest and to minimize trauma to the patient at both t point of entry and along the inside region of the conduit in which it is insert

Furthermore, the catheter should be designed so that the transducer does significantly alter the catheter's diameter, thereby minimizing flow occlusi thrombus formation and other mechanical traumas.

The catheter should also have a high lumen count, in other words, a relati ly large number of independent lumens, so that several types of information c be collected and a variety of treatments performed. In addition, the lum should have relatively large cross sections, especially when they are employed measure pressures via a fluid connection between the distal and proximal ends the catheter. The construction of a catheter having a small diameter, however, in direct conflict with the provision of a high lumen count and large lumen cr section. The flexibility of the catheter should also be designed to provide an opti balance between the catheter's maneuverability through tortuous passageways a its tendency to kink and old. Furthermore, it is essential that the flexibility uniform over the length of the catheter to further reduce the probability of kin ing due to the forces applied on flexible sections of the catheter by other, rel tively inflexible, sections during insertion.

Finally, because catheters are used invasively, they are conventional disposed of after a single use. Thus, it is desirable to keep the catheter's unit co as low as possible. For that reason, the construction of the catheter should simple and involve a minimum expense. Further, the electrical and mechanic coupling of a transducer to the catheter should be straightforward.

In view of the preceding remarks, it would be desirable to provide a smal diameter multifunction catheter that is capable of carrying a coaxially mount ultrasound transducer that has a high lumen count and large lumen cross-section area, and that is uniformly flexible and easy to construct.

Summary of the Invention In accordance with this invention, a catheter is provided including an exte nal tube and an internal tube. The external tube has proximal and distal ends a is provided with a primary lumen and a plurality of secondary lumens. The pr mary lumen is roughly circular in cross section and each of the secondary lume roughly defines a segment of an annulus in cross section. The internal tube al has proximal and distal ends and is provided with a plurality of inner tu lumens. Each inner tube lumen roughly de ines a circular sector in cross sectio The internal tube is receivable within the primary lumen of the external tube. In accordance with another aspect of this invention, the catheter includes a ultrasound transducer attached adjacent the distal end of the external tube. coaxial cable, receivable within one of the secondary lumens, is connectable t the ultrasound transducer. The internal tube is further made of a first materi having a hardness of Shore D65 and the external tube is made of a second materi having a hardness of Shore A93. Thus, the internal tube is relatively rigid and th external tube is relatively flexible.

Brief Description of the Drawings

The invention will presently be described in greater detail, by way of exa ple, with reference to the accompanying drawings, wherein: FIGURE 1 is an isometric view of a catheter constructed in accordance wit this invention; FIGURE 2 is an isometric view of a number of segments of the catheter FIGURE 1;

FIGURES 3A and 3B are sectional views of the catheter of FIGURES 1 an along the section lines A— A' and B--B' of FIGURE 2; FIGURE 4 is a sectional view of a segment of the catheter illustrating connection of a transducer thereto;

FIGURE 5 is an exploded isometric view of a connector shown in FIGURE FIGURE 6 is a sectional view of the connector of FIGURE 5; and FIGURE 7 is a block diagram illustrating a control and processing syst used with the catheter of FIGURE 1.

Detailed Description of the Preferred Embodiment Referring now to FIGURE 1, a catheter 10 constructed in accordance w this invention is shown. As will be described in greater detail below, catheter is easy to use, durable, simply constructed, and able to perform a variety functions. In that regard, the embodiment of the catheter shown is designed intravascular use to infuse therapeutic fluids, extract blood samples, prov electrical or optical communications between ends of the catheter, determi blood pressure, and determine cardiac output by Doppler ultrasound techniques. As shown in FIGURE 1, the catheter 10 includes an internal tube 12, exter tube 14, ultrasound transducer 16, sensor 18, and termination assembly 20. T internal tube 12 and external tube 14 collectively define a catheter body t supports the other components and allows them to be positioned at desired lo tions within an intravascular conduit of a patient. The transducer 16 and s sor 18 obtain information from the patient for use in diagnosis and treatment, will be described in greater detail below. The termination assembly 20 is coupl to both the internal tube 12 and external tube 14, and provides an interfa between the catheter 10 and a control and processing system 22.

Addressing the various components of catheter 10 individually, the inter tube 12 is an elongate piece of flexible tubing having defined therein thr lumens 26, 28, and 30. Tube 12 is preferably made of a standard medical gra flexible polyure thane having a hardness of Shore D65 and is roughly 115 cen meters long and 0.117 centimeter in diameter.

Lumens 26, 28, and 30 extend to the proximal end 32 of internal tube 12 a terminate at the termination assembly 20. Lumen 26 is known as a distal pressu lumen and extends from assembly 20, through the entire length of tube 12, to distal pressure port 34. Lumen 28 is known as a balloon lumen and extends from assembly 20 thro the length of tube 12. Lumen 28 opens to the exterior of tube 12 at a ballo port 36 approximately five millimeters from the distal end 38 of tube 12. Final lumen 30 is known as a sensor lumen and also extends from assembly 20 throu the length of tube 12. Lumen 30 opens to the exterior of tube 12 at a sen port 40 about forty millimeters from the distal end 38 of tube 12.

As shown in FIGURES 3A and 3B, lumens 26, 28, and 30 each define a cir lar sector when viewed in cross section. The distal pressure lumen 26 has t largest cross-sectional area (roughly 0.5 square millimeter). In contrast, t balloon and sensor lumens 28 and 30 are smaller in cross-sectional area (roug

0.3 square millimeter each), but adequate for the assigned functions. The lume 26, 28, and 30 are defined by walls of tube 12 that are of uniform thickn (roughly 0.125 millimeter).

From the foregoing, it is clear that tube 12 is provided with a relative large number of usable lumens. Furthermore, when compared to convention lumens of circular cross section provided in a catheter of the same diameter, ea lumen 26, 28, and 30 has a relatively large cross-sectional area. For example, t distal pressure lumen 26 has a cross-sectional area comparable to that of t distal pressure lumen of a conventional eight French (2.67 millimeters in dia eter) thermodilution catheter, despite the fact that the diameter of tube 12 smaller (0.117 centimeter). This is an important advantage since it allows lume having suitable pressure measurement characteristics to be included in a cathet having a diameter that is smaller than standard eight French devices.

The external tube 14 is an elongate piece of tubing and has five lumens 4 48, 50, 52, and 54 provided therein. Tube 14, like tube 12, is made of a medic grade polyurethane, but has a hardness of Shore A93, making it relatively mo flexible than the internal tube 12. The external tube 14 is roughly 105 cent meters long and 0.264 centimeter in diameter.

Addressing the various lumens 46, 48, 50, 52, and 54 individually, the cent lumen 46 extends between the proximal end 56 and distal end 58 of tube 14 and designed to receive the internal tube 12. Thus, as shown in FIGURE 3A, t internal lumen 46 has a circular cross section and is slightly greater in diamet (roughly 0.122 centimeter) than the outer diameter of the internal tube 12. shown in FIGURE 1, internal tube 12 is longer than external tube 14 and exten from the distal end of internal lumen 46 by roughly 10 centimeters.

Lumens 48 and 50 are known as the first and second proximal pressur lumens, respectively. These lumens 48 and 50 begin at the termination assem 20 at the proximal end 56 of tube 14. The first proximal pressure lumen 48 t extends the length of tube 14 and opens to the tube's exterior at a first proxi pressure port 60 located approximately five millimeters from the distal end 58 tube 14. The second proximal pressure lumen 50 also extends the length tube 14 and is open to the exterior of tube 14 at a second proximal press port 62 located roughly 180 millimeters from the distal end 58 of tube 14.

Lumens 52 and 54 are known as the injection and transducer lead lume respectively. These lumens 52 and 54 begin at the proximal end 56 of tube 14 the termination assembly 20. The injection lumen 52 then extends the length tube 14 and is open to the exterior of tube 14 at an injection port 64 loca roughly 150 millimeters from the distal end 58 of tube 14. The transducer l lumen 54 similarly extends the length of tube 14 and is open to the tube's exter at a transducer lead port 66 located at the distal end 58 of tube 14. As shown in FIGURE 3A, lumens 48, 50, 52, and 54 each define a segment an annulus in cross section. In that regard, the cross-sectional area of lumens 50, and 52 is roughly 0.275 square millimeter each, while the cross-sectional a of lumen 54 is roughly 0.467 square millimeter to accommodate the transdu wiring. Lumens 48, 50, and 52 are spaced between the inner and outer surfaces tube 14. Lumen 54 is also evenly spaced between the inner and outer surfaces tube 14 but is approximately twice as large in cross section. As will be app ciated from FIGURE 3 A, with the internal tube 12 inserted in external tube the size and location of the various lumens result in a substantially uniform w thickness for lumens 48, 50, and 52. Addressing now the transducer 16, transducer 16 may be any one of a vari of suitable transducer types, but is preferably of a cylindrical construction. T transducer 16 is located at the intersection of the internal tube 12 and the ext nal tube 14 where it can be easily attached to tube 14 and the transducer wiri by a connector 70. As will be appreciated, the internal tube 12 can be position inside the external tube 14 before or after transducer 16 is attached with interference.

Turning now to a more detailed discussion of the construction of conne tor 70, reference is had to FIGURES 4, 5, and 6. As shown, the connector includes three components: a plastic collar 72 and a pair of flexible conducti ring clips 74 and 76. The plastic collar 72 includes a cylindrical wall 78 coupled a circular base 80. As shown in FIGURE 5, the diameter of collar 72 is roug equal to the diameter of transducer 16 and external tube 14.

The two coaxially aligned roughly cylindrical ring clips 74 and 76 ha enlarged rims 82 that are molded into the circular base 80 of collar 72. As show the ring clips 74 and 76 are spaced apart at the collar 72 by a distance correspon ing to the thickness t of the cylindrical transducer 16, but are slightly clos together at their projecting ends. Each ring clip 74 and 76 is interrupted by plurality of circumferentially spaced-apart slots 84, to define a plurality fingers 86, adding flexibility to the ring clips 74 and 76.

Because the projecting ends of the ring clips 74 and 76 are normally spac apart by a distance less than the cylindrical main element thickness t, when end of the transducer 16 is inserted between ring clips 74 and 76, they spre apart and apply a slight force to the cylindrical transducer 16 to maintain t desired electrical and mechanical interface. To further ensure this connectio some type of detent may also be used. As will be appreciated, a connector 7 constructed in this manner allows the desired mechanical and electrical conne tion to be easily and securely made to the transducer 16. Thus, the transducer 1 can be quickly removed and replaced as needed.

Addressing now the coupling of the two ring clips 74 and 76 of connector 7 to the transducer wiring 88, because a single cylindrical element 16 is employed, coaxial cable provided in lumen 54 can be conveniently used for transduc wiring. More particularly, the internal conductor of cable 88 is coupled to th internal ring clip 76 of connector 70 by solder or a conductive adhesive and, thu is coupled to the internal surface of transducer 16. Similarly, the external co ductor of cable 88, commonly known as the grounding shield, is coupled to th external ring clip 74 of connector 70 by solder or a conductive adhesive and, thu is coupled to an external surface of transducer 16. The use of coaxial cable 8 instead of conventional wires significantly enhances the overall flexibility o catheter 10.

The sensor 18 may be any one of a variety of devices including, for example a thermistor or fiber-optic cell. Sensor 18 is preferably positioned adjacent th sensor port 40 on the internal tube 12. Sensor 18 is coupled to the terminatio assembly 20 by electrical wires or an optical fiber 90 located in lumen 30.

Turning now to a discussion of termination assembly 20, assembly 20 allow the various components of control and processing system 22 to be coupled to th catheter 10. The termination assembly 20 includes a plurality of flexible tub ings 92, 94, 96, 98, and 100 coupled to the distal pressure lumen 26, balloo lumen 28, first proximal pressure lumen 48, second proximal pressure lumen and injection lumen 52. The tubings 92, 94, 96, 98, and 100, respectively, end i distal pressure connector 102, balloon connector 104, first proximal press connector 106, second proximal pressure connector 108, and thermal inject connector 110.

Tubings 92, 94, 96, 98, and 100 preferably have circular diameters and slightly oversized with respect to their respective lumens. Connections are m by forcing each tubing into the corresponding lumen and then encapsulating area. As a result, the connection is made luid tight and a strain relief is forme The termination assembly 20 also includes a transducer connector 112 sensor connector 114 connected to cable 88 and the electrical wires or opti fiber 90. As shown in FIGURE 1, these portions of the termination assembly are also encapsulated to relieve strain at the various component junctions.

The termination assembly 20 is designed to interface with the control processing system 22. In that regard, as shown in FIGURE 7, the control processing system 22 includes a distal pressure measurement system 116, ball inflation/deflation device 118, first proximal pressure measurement system 1 second proximal measurement system 122, injection device 124, ultrasonic card output processing system 126, and sensor monitoring system 128. The distal pressure measurement device 116 is fluid coupled by conn tor 102 and tubing 92 to the distal pressure lumen 26 of internal tube 12. A result, pressure in the intravascular conduit adjacent the distal pressure port 34 catheter 10 is transmitted to the distal pressure measurement device 116 wh an output is produced. Similarly, the first and second proximal pressure measu ment systems 120 and 122 are coupled by connectors 106 and 108 to tubings 96

98. Thus, the first and second proximal pressure lumens 48 and 50 within exter tube 14 are in fluid communication with the first and second proximal press measurement systems 120 and 122. As a result, fluid pressure in the intravascu conduit adjacent the first and second proximal pressure ports 60 and 62 is tra mitted to systems 120 and 122, where outputs are produced.

The balloon inflation/deflation device 118, which may, for example, b syringe, is selectably engagable with connector 104 of termination assembly 20 introduce or withdraw gaseous fluid from lumen 28. Because lumen 28 is in flui communication with balloon 42, the injection of gaseous fluid into lumen induces an expansion of balloon 42, while the withdrawal of gaseous fluid the from results in a retraction of balloon 42. In this manner, the volume of b loon 42 can be controlled by the health care provider.

As previously noted, the sensor 18 may be either a thermistor or a fibe optic cell. With a thermistor employed as sensor 18, injection lumen 52 is coupl to the injection device 124 via the connector 110 provided in the terminati assembly 20. During actual clinical use, a bolus of cold fluid is injected into t blood at port 64 via the injection lumen 52. The bolus is then swept past t thermistor 18, which produces an electrical signal in response to the changin temperature caused by the injection. This electrical signal is carried by t thermistor wires 90 in lumen 30 to the sensor-monitoring system 128. In th embodiment, system 128 is a thermal dilution cardiac output computer that mon tors the temperature change over time to calculate the instantaneous cardia output.

Alternatively, a fiber-optic cell may be employed as sensor 18 to monit physical or chemical parameters of the fluid surrounding catheter 10. Lumen 3 now carries the fiber-optic strand or strands 90 that transceive optical signa between the cell 18 and the monitoring system 128. In this embodiment, sys tem 128 is an optical computer that converts the optical signals into digital ele tronic signals that are, in turn, processed by a digital computer to produce th appropriate readouts of the physical or chemical parameters being monitored. A will be appreciated, unlike the thermal dilution application discussed above, th injection lumen 52 is now available for the infusion of therapeutic fluids.

Finally, an ultrasonic cardiac output-processing system 126 is coupled b connector 110 of termination assembly 20 to the coaxial cable 88 and, hence, th ultrasound transducer 16. The transducer responds to electrical pulses fro cable 88 by emitting ultrasonic energy. Ultrasonic energy reflected by the flow ing blood is, in turn, transformed into electrical signals by the transducer 16 These signals are transmitted by coaxial cable 88 to system 126. The ultrasoni cardiac output-processing system 126 determines the Doppler frequency shif induced by the flowing blood and uses that information to compute blood low. Addressing now the overall operation of catheter 10, the distal end of cathe ter 10 is inserted into an appropriate blood vessel and balloon 42 inflated. In thi manner, catheter 10 is advanced until it passes through the superior vena cava the right atrium, the tricuspid valve, the right ventricle, and into the main pulmo nary artery. During the advancement of the catheter 10, pressure at the dista pressure port 34, first proximal pressure port 60, and second proximal pressur port 62 may be measured via systems 116, 120, and 122 to assist in positioning o - li ¬

the catheter within the pulmonary artery. In addition, the Doppler signals p duced by transducer 16 will be analyzed by the ultrasonic cardiac outp processing system 126 to provide an output that is position dependent. catheter 10 will then be advanced until the outputs of all four systems indic that the desired position in the pulmonary artery has been reached.

At this time, the cardiac output-processing techniques described above be employed to continuously determine cardiac output. In addition, the sensor may also be used to produce an output indicative of the physical or chemi parameters it senses. The catheter 10 described above has a number of advantages over conv tional catheter designs. In that regard, catheter 10 has an extremely high lu count for its size. More particularly, catheter 10 is able to provide seven lum for intravascular applications in which the catheter 10 has an outer diameter 0.26 centimeter. The ability to achieve such a high lumen count is a function the geometry adopted for both the lumens and catheter.

In addition to having a high lumen count, catheter 10 also allows the lum to have relatively large cross-sectional areas. As will be appreciated, this particularly important in applications in which the lumens are required for fl communication without obstruction. This is especially true for lumens used communicate pressure changes for use in pressure measurement.

The stepped, dual-diameter coaxial construction of catheter 10 is a advantageous. More particularly, if catheter 10 had a uniform diameter over entire length, the transducer 16 would necessarily project from the cathe surface. With the transducer 16 projecting from the surface of catheter transducer 16 would be exposed to a greater risk of thrombus formation and wo potentially introduce variations into the flow of fluid across the catheter 10. employing the internal tube 12 and external tube 14 to produce a catheter having a stepped configuration, however, a cylindrical transducer 16 can be eas added to the end of the external tube 14, before or after the internal and exter tubes 12 and 14 are joined, overcoming these limitations. The use of connector further simplifies the attachment of transducer 16 to tube 14.

The catheter 10 is also constructed to ensure roughly uniform flexibility t entire length of the catheter 10. In that regard, internal tube 12 is made o more rigid material than external tube 14. Thus, although internal tube 12 ha comparatively small diameter, it will retain a significant portion of the rigid exhibited by the external tube 14. As a result, the internal tube 12 resists tendency to collapse upon insertion, making catheter 10 easier to introduce i the patient's vascular system.

Finally, the catheter 10 is constructed to be relatively flexible. Conv tional catheters were limited by the relatively stiff wiring used in connection w sensors carried by the catheters. As described above, however, the disclos catheter 10 employs a single cylindrical ultrasound transducer 16 allowing a sin coaxial cable 88 to be easily employed. With a braided external conductor an thin internal conductor, coaxial cable 88 is quite flexible. Thus, the overall fle bility of the catheter 10 is improved. Those skilled in the art will recognize that the embodiments of the inventi disclosed herein are exemplary in nature and that various changes can be ma therein without departing from the scope and spirit of the invention. In t regard, the invention is readily embodied for use in a variety of conduits and f use with various types of ultrasound transducers 16. Further, it will be recogniz that the applications employed for the various lumens, as well as the componen of the termination assembly 20 and control and processing system 22 can varied. Because of the above and numerous other variations and modificatio that will occur to those skilled in the art, the following claims should not limited to the embodiments illustrated and discussed herein.

Claims

The embodiments of the invention in which an exclusive property or privil is claimed are defined as follows:

1. A catheter comprising: an external tube having proximal and distal ends and being provided wit primary lumen and a plurality of secondary lumens, said primary lumen be roughly circular in cross section and each said secondary lumen roughly definin segment of an annulus in cross section; and an internal tube having proximal and distal ends and being provided wit plurality of internal tube lumens, each said internal tube lumen roughly definin circular sector in cross section, said internal tube being receivable within s primary lumen of said external tube.

2. The catheter of Claim 1, further comprising: a cylindrical ultrasound transducer attached adjacent said distal end of s external tube; and a coaxial cable, receivable within one of said secondary lumens and conne able to said ultrasound transducer.

3. The catheter of Claim 2, wherein said internal tube is longer than s external tube and said distal end of said internal tube extends from said distal of said external tube.

4. The catheter of Claim 3, wherein said internal tube is made of a fi material having a hardness of Shore D65 and wherein said external tube is made a second material having a hardness of Shore A93, said internal tube being re tively rigid and said external tube being relatively flexible.

5. The catheter of Claim 1, wherein said secondary lumens of s external tube comprise a first proximal pressure lumen, a second proximal pr sure lumen, an injection port lumen, and a wiring lumen, and wherein said inter tube lumens include a distal pressure lumen, a balloon control lumen, and a wiri lumen.

6. The catheter of Claim 5, wherein said wiring lumen of said exter tube has a larger cross-sectional area than said first proximal pressure lum second proximal pressure lumen, and injection port lumen of said external tu and wherein said distal pressure lumen of said internal tube has a larger cro sectional area than the balloon control lumen and wiring lumen of said inter tube.

7. The catheter of Claim 5, wherein said first proximal pressure lum second proximal pressure lumen and injection port lumen are radially spac roughly the same distance from said internal tube lumens as they are from t exterior of said external tube.

8. The catheter of Claim 1, further comprising: a sensor coupled to said internal tube; and communication means, receivable within one of said internal tube lume and connectable to said sensor for communication with said sensor.

9. The catheter of Claim 8, wherein said sensor comprises a thermist and said communication means comprises an electrical conductor.

10. The catheter of Claim 8, wherein said sensor comprises an optical c and said communication means comprises an optical fiber.

11. A catheter comprising: an internal tube having proximal and distal ends; an external tube having proximal and distal ends and being provided wi first and second lumens, said first lumen being for receiving said internal tube; a cylindrical ultrasound transducer mounted coaxially on said external tub adjacent said distal end; and a coaxial cable, received within said second lumen of said external tub coupled to said ultrasound transducer.

12. A catheter comprising: an internal tube, made of a first material having a hardness of Shore and an external tube, having a lumen for receiving said internal tube, made second material having a hardness of Shore A93, said internal tube being relat rigid and said external tube being relatively flexible.

13. A method of producing a catheter comprising the steps of: providing an external tube, having proximal and distal ends, a primary lu and a plurality of secondary lumens, said primary lumen being roughly circul cross section and each said secondary lumen roughly defining a segment annulus in cross section; and providing an internal tube in said primary lumen of said external tube, internal tube having a plurality of internal tube lumens, each said internal lumen roughly defining a circular section in cross section.

14. An assembly, for use with an ultrasonic transducer, comprising: connection means for providing a detachable electrical and mecha coupling with the ultrasonic transducer; and carrier means for supporting said connection means.

15. The assembly of Claim 14, wherein said connection means compri conductive clip for engaging the ultrasonic transducer.

16. The assembly of Claim 15, wherein said conductive clip includ pair of axially aligned, roughly cylindrical clip fingers for engaging the ultras transducer therebetween.

17. The assembly of Claim 16, wherein said carrier means further c prises a nonconductive holder for housing said clip.