Patent Description:
Conventional pressure catheters may require a supplemental source of gas to refill the balloon due to gas diffusion out of the balloon during the procedure. The use of supplemental gas allows the balloon to continue to sense pressure changes within the body of the patient. In addition, dead space within the lumen reduces the ability of the pressure sensor to take accurate measurements over small discrete intervals. <CIT> describes a device for continuously measuring intra-abdominal pressure, the device comprising a lumen configured to connect to a pressure transducer, and a compensation chamber in fluid communication with the lumen and a urinary catheter. <CIT> describes a pressure sensing catheter which includes, in its proximal end, a transducer base or housing that is permanently attached to the catheter shaft. The base includes, inserted thereinto, one or more miniaturized pressure transducer assemblies, which are in fluid communication with corresponding pressure lumens that extend down the shaft and are in communication with one or more predetermined balloons by discrete channels or ports, which provide a fluid passage between the interior space of the balloon and the corresponding pressure lumen. <CIT> describes a gas column pressure-measuring catheter which is insertable into a mammalian body for purposes of transmitting pressure changes from a location within the mammalian body to a pressure sensor which is either incorporated into, or connected to, the catheter. The gas column pressure-measuring catheter comprises an elongate catheter body having a gas-filled lumen extending longitudinally therethrough, and a gas-filled membrane-walled chamber positioned on the catheter body in communication with the gas-filled lumen such that pressure changes exerted against the outer surface of the membrane-walled chamber will result in the transmission of pressure changes through the gas-filled catheter lumen. The gas-filled membrane-walled chamber may be located on the side wall of the catheter body or on the distal end of the catheter body. <CIT> describes a catheter including a distal distension balloon and circumferentially arranged motility measurement balloons proximal of the distension balloon, a manifold including balloon ports each configured to fluidly couple to a motility measurement balloon, pressure transducer ports, and a priming port. A port selector is coupled to the manifold and movable between different positions. Each port selector position causes the manifold to establish different fluidic couplings between the respective motility balloon, pressure transducer, and priming ports. A pressure sensing device includes pressure transducers each fluidly coupled to one of the pressure transducer ports. The pressure sensing device is configured to coordinate calibration of the pressure transducers at atmospheric pressure with the port selector in a first position and motility balloon pressure measurements with the port selector in a third position. Priming of the motility measurement balloons is implemented by moving the port selector to a second position.

The scope of the present invention is defined by the scope of the appended claims. All embodiments which do not fall under the scope of the appended claims are examples which are useful to understand the invention, but do not form a part of the present invention.

In one aspect, this disclosure provides a pressure-sensing catheter for detecting pressure changes within a cavity of a patient. The pressure-sensing catheter comprises an elongate member comprising a proximal end, a distal end and a central lumen extending from the proximal end to the distal end. Further, the pressure-sensing catheter comprises a monitor lumen positioned within the elongate member and extending from the proximal end to the distal end, the monitor lumen having a volume of <NUM> microliters to <NUM> microliters. The pressure-sensing catheter may have a hollow pressure-compliant member defining an interior chamber in fluid communication with the monitor lumen. The pressure-compliant member can be disposed about an exterior of the elongate member, wherein the monitor lumen and the interior chamber of the pressure-compliant member define a fluid column. A connector apparatus can be disposed about the proximal end and be in fluid communication with the monitor lumen, and can comprise a first complementary connector and a second complementary connector, at least one of which can be fluidly coupled to the fluid column, defined by the pressure-compliant member. Further, one of the first complementary connector and the second complementary connector can have a pressurizing device and the other of the first complementary connector and the second complementary connector can have a bore. The pressurizing device can displace a volume of fluid located within the bore into the fluid column, wherein the ratio of the volume of displaced fluid to the volume of the fluid column ranges from about <NUM>:<NUM> to less than about <NUM>:<NUM>.

In another aspect, the pressure catheter can comprise a radio-opaque band circumscribing the exterior of the elongate member and being disposed within the interior chamber of the pressure-compliant member.

In a further aspect, a method of detecting pressure changes within a cavity of a patient, comprises the step of advancing a catheter such as those disclosed according to any embodiment herein within the cavity of a patient. The method can involve the step of displacing a volume of fluid within the connector apparatus to the fluid column, wherein the ratio of the volume of displaced fluid to the volume of the fluid column ranges from approximately <NUM>:<NUM> to less than about <NUM>:<NUM> (e.g., about <NUM>:<NUM>). Further, the method can comprise measuring changes to the pressure within the fluid column resulting from the contraction of tissue about the pressure compliant member.

For purposes of illustrating the various aspects of the methods and systems claimed herein, the discussion below will be directed to describing exemplary embodiments used in urodynamic pressure sensing. It should be noted, however, that the elements and principles discussed herein are applicable to other applications. For example, the exemplary embodiments described herein are contemplated for use with any type of catheter wherein measurement of pressure within the body of a patient is desired. Further, discussion of methods and systems herein can be interchangeable with respect to specific aspects. In other words, specific discussion of one method or system (or components thereof) herein is equally applicable to other aspects as they relate to the system or method, and vice versa.

<FIG> is a perspective view of a catheter in accordance with a non-limiting exemplary embodiment. As shown in <FIG>, a pressure monitoring catheter <NUM> is disclosed comprising an elongate flexible fluid column catheter that is connectable to a pressure sensing apparatus by way of connector <NUM>. An elongate center arm <NUM> extends from the proximal end <NUM> of the catheter <NUM> to a connector <NUM>. The connector <NUM> in turn can be used to attach a syringe or other device used for the collection (e.g. aspiration) or delivery (e.g. infusion) of fluids to or from the cavity of the patient through holes <NUM> at the distal end <NUM> of the catheter <NUM>. A data/power cable or wireless transmitter (not shown) connects the pressure sensing apparatus to a processor and monitor and/or database.

The catheter <NUM> can be detachably attached to a cable assembly which is structured to be coupled (either wired or wirelessly) to a processor and monitor. In one aspect where the cable assembly comprises a wired reusable assembly, the reusable interface cable assembly has, at its proximal end, an electrical connector configured to be connected to a processor and a monitor. In the aspect where the cable assembly is wirelessly coupled to a processor and/or monitor, the proximal end of the cable assembly comprises a wireless transmitter.

With reference to <FIG>, the distal end <NUM> of the catheter <NUM> comprises a soft, pliant tip <NUM>, which facilitates insertion of the catheter <NUM> into the patient. The soft tip <NUM> may preferably be formed of a material pliant enough to deflect or give as the tip <NUM> encounters a resistive force, such as the wall of the bladder. A low durometer plastic or elastomer, such as polyvinyl chloride (PVC) or polyurethane, is suitable, though other materials having a suitable rigidity/pliancy and are safe for use inside a patient can be used. The tip <NUM> can be formed from an elongated hollow tube <NUM> which extends from the tip <NUM> at its distal end <NUM> to one or more connector <NUM> on its proximal end <NUM>.

With continued reference to <FIG>, the hollow tube <NUM> can be formed of flexible, biocompatible material, such as PVC or a polyolefin, with sufficient properties, such as wall thickness, to resist collapse under normal conditions, and sized in length to extend from within a cavity (e.g., the alimentary canal or urinary tract) of a patient to outside the body of the patient. Thus, for example, the hollow tube <NUM> may range in length from <NUM> to <NUM>.

<FIG> is a portion of the catheter of <FIG> to illustrate details thereof. As shown in <FIG>, a plurality of holes or apertures <NUM> are formed through the wall of the hollow tube <NUM> immediately behind the tip <NUM>. The number of holes <NUM> may vary, however. The holes <NUM> are distributed about the circumference of the outer hollow tube <NUM> and longitudinally about a distal end <NUM> of the catheter <NUM> to allow fluid to be aspirated or otherwise collected from the patient or infused or delivered into the patient during a procedure. A plurality of holes <NUM> is provided so that if any one or more holes <NUM> should become clogged or blocked, other holes <NUM> will be available for allowing passage of fluid. In an alternative aspect, slits, such as slit valves may be formed through the wall of the outer hollow tube <NUM> to provide for infusion and/or aspiration of fluids.

With continued reference to <FIG> and referring now to <FIG> and <FIG>, the catheter comprises a central lumen <NUM> and one or more secondary lumens <NUM> that are disposed within the hollow tube <NUM>. The central lumen <NUM> can be in fluid communication with holes <NUM>. Additionally, the central lumen <NUM> can also be in fluid communication with a lumen of the elongate center arm <NUM> (best seen in <FIG>). In some examples, the central lumen <NUM> has a hydraulic diameter ranging from about <NUM> to about <NUM> millimeters with a non-limiting exemplary diameter of <NUM> millimeters.

The secondary lumen <NUM> may be interchangeably referred to as "monitor lumen. " Returning to <FIG> and <FIG>, each monitor lumen <NUM> comprises one or more flexible, biocompatible materials, such as polyurethane and is integrally formed from or with the sidewall of the hollow tube <NUM>. The secondary lumen <NUM> is sized in diameter to fit within the hollow tube <NUM> and to leave adequate space for passage of fluids through central lumen <NUM>. Referring now to <FIG>, the secondary lumen <NUM> extends from the connector <NUM>, (and sealed therewith), to the distal end <NUM> of the catheter <NUM>. As seen from <FIG>, the secondary lumen <NUM> extends from the hollow tube <NUM> of the catheter <NUM> body to the connector <NUM> by way of a flexible extension arm <NUM> which is integrally formed with the elongate hollow tube <NUM>.

Referring back to <FIG> and <FIG>, a flaccid, pressure-compliant member (e.g., a balloon) <NUM> can be in fluid communication with the secondary lumen <NUM> and is positioned about the relatively non-compliant hollow tube <NUM>. The pressure-compliant member <NUM>, which is fluid-filled in one aspect, is structured to deflect or deform upon application of a force thereto, (e.g. an increase in pressure within the body cavity from the contraction of tissues within the body), and to expand again upon removal of the force therefrom (e.g. a subsequent decrease in pressure after a relaxation of the contracting tissues). Therefore, a particularly suitable pressure-compliant member <NUM> may be a medical grade balloon <NUM> formed of a thin-walled, flexible, low durometer material such as C-Flex® elastomer, which is relatively easily deformed with a small increase in pressure.

With reference to <FIG> and <FIG>, the balloon <NUM> may be formed as a substantially circular body disposed about and/or attached to an opening <NUM> of a secondary (or monitor) lumen <NUM> and/or heat-sealed at the ends <NUM> of the balloon <NUM>. While a circular shape is illustrated, other shapes may be used. Fluid (e.g., air) may occupy the interior of the secondary lumen <NUM>. In such cases, fluid may be at atmospheric pressure prior to use of the catheter <NUM>. The secondary lumen <NUM> and the balloon <NUM> attached to the secondary lumen <NUM> (including any portion of the secondary lumen <NUM> that extends within the connector <NUM>) may, therefore, form or define a fluid column which extends from inside the connector <NUM> to near the tip <NUM> of the catheter <NUM>. When the catheter <NUM> is attached to complementary connector, as explained further below, the fluid column becomes filled, or "charged," with an additional quantity of fluid. The additional fluid charged into the fluid column partially fills the balloon <NUM> to a selected volume.

The material of the balloon <NUM> can be substantially pliant due to its thin wall and the low durometer material used in its construction, and the balloon <NUM> deforms easily and substantially with a given change in pressure external to the balloon <NUM>. Further, the balloon material may not introduce any artifacts during pressure measurements. The material of the balloon <NUM> may, for example, have a Shore durometer hardness of about <NUM> A. Examples of materials for the secondary lumen <NUM> may be C-Flex® synthetic elastomer of <NUM>-<NUM> millimeters wall thickness, or any other similar material having similar durability and flexibility or other material having characteristics suitable for the designs and use specified herein. Regardless of the material employed, in some examples, less than <NUM> millimeters of mercury (Hg) of maximum external pressure may collapse the balloon <NUM> when its interior is vented to atmospheric pressure, though the balloon <NUM> can be designed to be operable at pressure ranges ranging from <NUM> millimeters Hg to <NUM> millimeters Hg. The collapse of balloon <NUM>, before charging the fluid column as described, provides an accurate pressure signal.

With reference to <FIG>, the balloon <NUM> may be attached to an end of the secondary or monitor lumen <NUM> in any appropriate manner. However, as illustrated in <FIG>, the balloon <NUM> can be attached to the secondary lumen <NUM> by positioning the balloon <NUM> over opening <NUM> of the secondary lumen <NUM> and securing the balloon <NUM> about the circumference of the opposing ends <NUM> of the balloon <NUM>. The balloon may be secured by laser welding, adhesive bonding, RF welding, induction welding, hot air welding, or other suitable methods for securing balloon <NUM> to the catheter <NUM>.

As seen from <FIG> and <FIG>, the balloon <NUM> can be positioned about the exterior of the hollow tube <NUM> so that the interior volume of the balloon <NUM> is substantially laterally aligned with the apertures or opening <NUM> formed through the hollow tube <NUM> so as to be in fluid communication with the secondary (or monitor) lumen <NUM>. Thus, the balloon is in fluid communication with the secondary lumen <NUM> and the charge-volume of fluid from the connector apparatus. While a single opening <NUM> is shown as providing fluid communication with the secondary lumen <NUM>, in other aspects of the disclosure more than one opening may be present within a single balloon <NUM> corresponding to a single secondary lumen <NUM>. In certain exemplary embodiments, more than one secondary lumen <NUM> (as shown more fully in <FIG>) is used as more than one sensor balloon <NUM> is disposed about the catheter <NUM>.

As may be appreciated, too high an internal fluid column pressure can reduce the sensitivity of the device for measuring pressure changes and may increase the susceptibility of the pressure monitoring to temperature-induced artifacts. Balloon <NUM> may burst due to its relatively fragile construction if over-pressurized. Accordingly, some such exemplary embodiments provide optimal balloon diameter and fluid column pressure. Further, some exemplary embodiments of the current disclosure balance total volume of the fluid column according to the volume of fluid within the secondary (or monitor) lumen <NUM>, the total volume available within the balloon <NUM>, and the balloon charge volume.

In accordance with one aspect of the disclosure, prior to placement on the catheter <NUM>, the balloon <NUM> has a length ranging from about <NUM> millimeters to about <NUM> millimeters with one non-limiting exemplary length of about <NUM> millimeters. After the top and bottom portions of the balloon <NUM> are secured to the outside of the hollow tube <NUM> (e.g., through laser welding or other suitable method), the length of the inflatable portion of the balloon <NUM> can range from about <NUM> millimeters to about <NUM> millimeters with one non-limiting exemplary length of about <NUM> millimeters.

In some such aspects, the diameter of the balloon <NUM> can range from about <NUM> millimeters to about <NUM> millimeters with one non-limiting exemplary length of about <NUM> millimeters and the hollow tube <NUM> has an outer diameter ranging from about <NUM> millimeters to about <NUM> millimeters with one non-limiting exemplary diameter of about <NUM> millimeters. A balloon diameter that is too small may not provide enough space between the inner wall of the balloon <NUM> and the outer wall of outer tube <NUM> to create a sufficient amount of deflectable volume to accurately measure a patient-induced pressure event (e.g., coughing, flexing of alimentary canal tissues, etc.) before the balloon <NUM> "bottoms out" (e.g., touches) against the outer wall of the hollow tube <NUM>.

In some examples, life, maximum pressure, and accuracy of the balloon may be a function of the separation distance between the inflated balloon <NUM> and the outer wall of hollow body <NUM> the catheter <NUM>. As the pressure differential between the inside and outside of the balloon <NUM> increases, the balloon <NUM> may collapse and "wrinkle" toward the catheter <NUM>. Under pressure, the collapsing balloon <NUM> may wrinkle and bear upon the hollow body <NUM>, thus counteracting the external pressure with both internal pressure created from shrinking volume, and force applied against the hollow body <NUM>. As more force is transmitted from the balloon <NUM> to the hollow body <NUM>, the remaining internal force, as measured by the pressure transducer, becomes significantly lower than the actual external pressure.

In accordance with aspects of the present disclosure, a larger balloon diameter and a smaller catheter body create a larger "gap" between the wall of the balloon <NUM> and outside wall of the hollow tube <NUM>. As the inflated balloon <NUM> is subjected to the oxygen-poor urine, or other body fluid, oxygen molecules immediately begin permeation and diffusion across the balloon membrane, reducing the volume of the charged balloon immediately. While nitrogen molecules diffuse slower, and are contemplated for use as an inflation fluid herein, they too can also migrate across the balloon membrane. A larger gap, in such cases, may not slow loss of gas, but may provide a more tolerable level of loss, thus increasing balloon life. Even without loss of gas, the balloon <NUM> has a maximum measurable pressure where wrinkles (i.e., collapsing surface of the balloon <NUM>) touch the catheter <NUM>. A measure of this maximum pressure correlates with the catheter life due to loss of gas over time.

Some examples of the present disclosure minimize dead space within the system which affects system accuracy and balloon life. In one aspect, a minimum of about <NUM>% to <NUM>% of the total closed system volume needs to be "working volume" while the other <NUM>% to <NUM>% of the total close system volume comprises "nonworking volume. " The "working volume" comprises the volume of fluid within the balloon while the "nonworking volume" comprises the volume of fluid within the monitor lumen and the interstitial spaces in the connector mechanism. The collapsing balloon <NUM> may wrinkle inward to accommodate both the collapsing balloon volume and the densifying of the fluid in the nonworking volume. In one aspect of the disclosure, the ratio of working volume to nonworking volume is greater than <NUM>:<NUM> in an effort to optimize maximum balloon pressure, high-end pressure accuracy, and balloon life. Advantageously, the balloon geometry described herein optimizes the inward "wrinkle" of the balloon <NUM> so that it may not collapse on itself which may negatively affect balloon performance.

While a smaller catheter diameter (e.g., <NUM>-<NUM> Fr) and a slightly larger diameter for the balloon <NUM> are certain aspects of the present disclosure, a smaller catheter may put constraints on the diameter of the infusion lumen. In addition, too large a balloon <NUM> may be over constrained (e.g., pre-pressurized simply by its relative size within the patient) when inflated within the a body cavity (e.g., the urethra), causing overstated "resting tones" sensed without the patient "squeezing", but in a relaxed state. Accordingly, the ratios presented herein may be considered illustrative, and balanced during practical use.

In one aspect of the disclosure, the internal volume of the balloon <NUM> ranges from about <NUM> microliters to about <NUM> microliters with one non-limiting exemplary volume of <NUM> microliters. In one aspect, the diameter of the secondary (or monitor) lumen <NUM> ranges from about <NUM> millimeters to about <NUM> millimeters with one non-limiting exemplary diameter of <NUM> millimeters. Based on an exemplary total length of the secondary lumen <NUM> of <NUM> centimeters to <NUM> centimeters, the total volume of fluid within the secondary lumen <NUM> ranges from about <NUM> microliters to about <NUM> microliters with one non-limiting exemplary volume being <NUM> microliters. A charge volume (which may correspond to the amount of fluid introduced into the fluid column) can range from about <NUM> microliters to about <NUM> microliters with a non-limiting exemplary volume of about <NUM> microliters. The total volume of the fluid (e.g., air) column may be defined by the volume of the secondary (or monitor) lumen <NUM> and the interior chamber defined by the balloon <NUM> (e.g., the balloon volume). Accordingly, in one aspect of the disclosure, the volume of the fluid column can range from about <NUM> microliters to about <NUM> microliters with a non-limiting exemplary volume being about <NUM> microliters. As noted herein, the charge volume can refer to the total amount of fluid that is introduced into the fluid (e.g., air) column to "charge" or ready the catheter <NUM> for pressure measurement.

<FIG> illustrate various portions of the catheter and a complementary connector. While <FIG> illustrates details of a first complementary connector <NUM>, <FIG> illustrates details of a second complementary connector <NUM> that can receive the first complementary connector <NUM>. <FIG> illustrates a sectional view of the second complementary connector <NUM> while <FIG> is a front view of a connected orientation of the first complementary connector and the second complementary connector. Referring to <FIG>, the first complementary connector can be fixedly attached to the proximal end of the elongate member and comprises an internal lumen in fluid communication with the monitor lumen.

Referring to <FIG> and <FIG>, the second complementary connector can be removably connected to the first complementary connector. Referring to <FIG> and <FIG>, the second complementary connector <NUM> has an internal bore or cavity <NUM> that is sized in internal diameter and length to frictionally receive the first complementary connector <NUM> (shown in <FIG>) of the catheter <NUM>. Upon insertion of the first complementary connector <NUM> in the bore <NUM> of the second complementary connector <NUM>, the O-ring <NUM> becomes seated against an inner wall of the internal bore <NUM> to form a fluid-tight fit.

As seen in <FIG>, the bore <NUM> and charging section <NUM> lying between the engagement section <NUM> of the second complementary connector <NUM> and the enclosure <NUM> of the proximal coupler <NUM> define an internal space <NUM> which contains a predetermined or selected volume of fluid (e.g., the charge volume) prior to insertion of the first complementary connector <NUM> into the bore <NUM> of second complementary connector <NUM>. Thus, in an example, as the first complementary connector <NUM> is inserted so as to act like a pressurizing device (e.g., piston or plunger) into the bore <NUM> of second complementary connector <NUM>, part of the volume of fluid contained within the internal space <NUM> of the bore <NUM> is displaced by first complementary connector <NUM> through the end <NUM> of monitor lumen <NUM> adding the volume of fluid to the fluid column. The displaced volume of fluid may be sufficient to "charge" or partially fill the balloon <NUM> with an appropriate amount of fluid to expand the balloon <NUM> to function with desired sensitivity responsive to a given range of pressure values. In other words, the effective fluid volume trapped in the fluid column is defined by the inward stroke or travel of first complementary connector <NUM>, and its related components, from the point at which O-ring <NUM> passes flutes <NUM> until first complementary connector <NUM> is fully inserted in second complementary connector <NUM>.

Referring again to <FIG>, at the distal end of the cable is a pressure detection device <NUM> which, when coupled to the catheter <NUM> by way of connector <NUM> (illustrated in <FIG>), interfaces with the fluid column of the catheter <NUM> to detect changes in pressure (e.g., urodynamic pressure). With continued reference to <FIG>, a proximal extremity <NUM> of the enclosure <NUM> and the open proximal end <NUM> of the monitor lumen <NUM> are positioned in close proximity to the pressure detection device <NUM> housed within the enclosure <NUM>, minimizing dead space in the system. The pressure detection device <NUM> may be, in a non-limiting example, a pressure transducer having a deformable diaphragm positioned toward the engagement section <NUM> of the second complementary connector <NUM>. Wiring <NUM> extends from the pressure transducer through the enclosure <NUM> and to the proximal end of the cable <NUM> for communication to a processor.

With reference to <FIG>, the pressure detection device <NUM> is operable with a proximal coupler <NUM> structured within a second complementary connector <NUM>, the proximal coupler <NUM> being sized to receive a first complementary connector <NUM> (illustrated in <FIG>) from connector <NUM> of the catheter <NUM>. The second complementary connector <NUM> has an enclosure <NUM> for housing the pressure detection device therein and an end cap <NUM> for capping the enclosure <NUM> and attaching the pressure detection device <NUM> to a tubular cable <NUM> of the reusable interface cable assembly. A protective cover <NUM> may also be provided on the reusable interface cable assembly sized to fit over the second complementary connector <NUM>.

Upon insertion of the catheter <NUM> into the body cavity, the balloon <NUM> may be in a substantially deflated state. With charging, the balloon <NUM> becomes at least partially filled with fluid (e.g., air). Thus, depending on how much fluid is in the balloon <NUM> prior to charging, the balloon <NUM> may be anywhere from <NUM>% to <NUM>% filled to capacity with fluid following charging. In some examples, the balloon <NUM> may not be overfilled so as to reduce the chances of the structure of the balloon <NUM> being introduced into the signal. In other words, the flaccidity of the partially-filled working volume of balloon <NUM> can reduce the occurrence of aberrant effects in pressure detection due to temperature changes (for instance, from Charles's Law), or undesirable effects that may introduce signal artifacts due to the balloon wall internal forces, or external balloon compression from debris.

The low durometer material of the balloon <NUM> allows the surface of the balloon <NUM> to deform with an increase in pressure. Therefore, a minimum of <NUM> millimeter Hg increase in body cavity pressure may cause deformation of the balloon <NUM> and, in turn, modify the pressure in the fluid column within the balloon <NUM> and secondary lumen <NUM>. The change in pressure is translated down the fluid column to the diaphragm of the pressure detection device (best seen in <FIG>). Deflection of the diaphragm resulting from an increase in pressure can be converted to an electrical signal by the transducer and is relayed to the monitor through the cable <NUM> or wirelessly. Similarly, a subsequent decrease in body cavity pressure can also be relayed by subsequent expansion of the balloon <NUM>. While a pressure transducer has been specifically described, other means of detecting pressure changes known in the art are contemplated for use herein.

Advantageously, aspects of the present disclosure provide for wider pressure ranges. The larger diameter balloon <NUM> and outer tube <NUM> combination allows the catheter <NUM> to measure a larger pressure range before "bottoming" out against the outside wall of the outer tube <NUM>. Moreover, the balanced ratio of charge volume, secondary or monitor lumen volume, and balloon volume/geometry may optimize the sensitivity of the system to better measure cavity pressure. In addition, the balancing of these elements may minimize damping of the pressure signal which increases the speed and resolution of the pressure measurements within the patient.

In accordance with an aspect of the disclosure, the ratio of the volume of fluid displaced (e.g., charge volume) to the volume of the fluid (e.g., air) column ranges from about <NUM>:<NUM> to about <NUM>:<NUM> with a non-limiting exemplary range of <NUM>:<NUM> to <NUM>:<NUM>. In other words, in an aspect of the disclosure, the charge volume of the catheter <NUM> is approximately ½ to ¾ of the volume of the fluid column. Advantageously, such embodiments maximize space (and/or volume of fluid) available for charging while also increasing the range of pressure measurements.

In another aspect, the ratio of the longitudinal length of the balloon <NUM> to diameter of the balloon <NUM> ranges from about <NUM>:<NUM> to about <NUM>:<NUM>. In another aspect of the disclosure, however, the ratio of the longitudinal length of the balloon <NUM> to the diameter of the balloon <NUM> ranges from about <NUM>:<NUM> to about <NUM>:<NUM>. The ratio of the diameter of the balloon <NUM> to the diameter of the outer tube <NUM> may also be a factor in precision operation of aspects of the disclosure. In still another aspect of the disclosure, the ratio of the diameter of the outer tube <NUM> and the diameter of the balloon <NUM> ranges from <NUM>:<NUM> to <NUM>:<NUM>.

<FIG> and <FIG> show examples of improvements of the present disclosure over prior art catheters. <FIG> illustrates the test results of the operational frequency of signals detected by the pressure detection device located in the second complementary connector <NUM> over a course of tests. The test results demonstrate a significantly higher operational frequency of measurements. The higher operational frequency yields significantly more precise measurements of pressure as well as higher granularity or finer measurements of pressure changes. For example, a coughing event that creates contraction of tissues within the body is a "high-frequency" event that cannot be adequately detected with prior art devices.

<FIG> illustrates a plot of actual pressures applied to a pressure-compliant member plotted against a comparison of measured pressure and applied pressure. The test results demonstrate the improved ability of aspects of the disclosure to measure actual pressure applied to the pressure-compliant members particularly as the amount of pressure applied increases. Advantageously, the disclosure allows for greater amounts of beginning pressures within the balloon <NUM> which results in a longer lasting testing time.

In accordance with an aspect of the disclosure, and as best seen in <FIG>, a catheter marker band <NUM> can be provided on the catheter shaft. The marker band <NUM> can be a short, thin-wall tube or wire made from gold, tungsten, platinum or other dense metal and is placed on the a catheter shaft to provide high levels of visibility under fluoroscopy (radio-opacity). This can allow medical practitioners to precisely locate the catheter features deep within the body. In some examples, the marker band <NUM> can be made from compounding tungsten powder into a biocompatible polymer. Non-limiting examples of useable polymers include high-density polyethylene, polyamides, fluoropolymers (e.g., polytetrafluoroethylene), polyolefin, and PVC. While specific reference to tungsten is made herein, it is understood that other radiopaque materials are contemplated for use, including, but without limitation, platinum iridium, gold, tantalum, platinum, tungsten carbide, and the like. Such examples advantageously eliminate multi-step forming processes used in conventional devices to create seamless small diameter tubes or wire bundles and/or specialized manufacturing equipment to secure metal bands to the polymer catheter tip so that they do not fall off during use (e.g., a medical procedure). Accordingly, such examples of the present disclosure are less costly and time consuming relative to conventional devices whereby a metal band is provided on the catheter shaft.

In accordance with an aspect of the disclosure, tungsten is cryogenically ground to a powder having a particle size ranging from <NUM> to <NUM>. The tungsten powder is then placed in a batch mixer with polymer beads where it is heated and mixed together to form a polymer-tungsten composition. The resulting composition is formed into an elongate hollow tube from which the bands <NUM> are cut or otherwise created. Tungsten creates a dense band that is radiopaque in a fluid of radiopaque contrast media such as iodine or barium. In accordance with an aspect of the disclosure, bands <NUM> are customized using the same polymer specified for the catheter <NUM> shaft to allow heat bonding of the band <NUM> to the outer wall of hollow tube <NUM> for a more secure assembly.

In some examples, tungsten loadings within the thermoplastic polymer range from <NUM>% to <NUM>% by weight to meet radio-opacity requirements. The compounded, heated material is extruded into tubes that can be easily applied to the catheter <NUM>. For instance, the tungsten-polymer tube can be placed over the exterior of the catheter <NUM> so that it is frictionally fit (or otherwise secured) about the exterior of the outer tube <NUM>.

In some such examples, the interior diameter of the tungsten-polymer tube can be configured to approximate the outer diameter of the outer tube <NUM> of catheter <NUM>. Further, in certain aspects, the tungsten-polymer tube can be placed over the outer diameter of the outer tube <NUM> but within the balloon <NUM> (e.g., centrally within the balloon <NUM>). In some such aspects, the opening being surrounded by the hollow pressure compliant member, the radio opaque band <NUM> is circumscribed on the hollow tube <NUM> such that the radio opaque band does not cover the opening <NUM> on the monitor lumen <NUM>. In this manner, the precise location of each "sensor" (i.e., balloon <NUM>) is known to the practitioner. In this instance, the longitudinal length of the tungsten-polymer tube can be sized to be less than the longitudinal length of the balloon <NUM> as it is disposed on the catheter <NUM>. For example, in the instance where the longitudinal length of the functioning balloon is <NUM> millimeters, the longitudinal length of the marker band <NUM> formed from the tungsten-polymer tube is less than <NUM> millimeters and, in one non-limiting example, has a longitudinal length of <NUM> millimeters.

In another aspect of the disclosure, a plurality of marker bands <NUM> are laser welded or otherwise secured to the outside wall of the catheter <NUM> on opposing sides of balloon <NUM> and, for example, placed over the portion of the balloon <NUM> that is welded to the outside wall of catheter <NUM>. In this manner, the location of the balloon <NUM> within the patient is located between the two radio-opaque markers <NUM>. In this aspect, the marker bands <NUM> have a longitudinal length that ranges from <NUM> millimeters to <NUM> millimeters. In yet another aspect of the disclosure, a radiopaque cap or blunt end is formed from the composition referenced above and disposed about a distal end of the catheter <NUM>. The distal end of the catheter <NUM> is spaced a known distance from a balloon <NUM> on catheter <NUM> and therefore provides a marker within the body of the patient.

Claim 1:
A pressure-sensing catheter (<NUM>) for detecting pressure changes within a cavity of a patient, comprising:
an elongate member (<NUM>) comprising a proximal end (<NUM>), a distal end (<NUM>) and a central lumen (<NUM>) extending from the proximal end (<NUM>) to the distal end (<NUM>);
a first monitor lumen (<NUM>) positioned within the elongate member (<NUM>) between the central lumen (<NUM>) and a wall of the elongate member (<NUM>), the first monitor lumen (<NUM>) extending from the proximal end (<NUM>) to the distal end (<NUM>); and,
a first pressure-compliant member (<NUM>) defining an interior chamber, the first pressure-compliant member (<NUM>) being hollow and in fluid communication with the first monitor lumen (<NUM>), the first pressure-compliant member (<NUM>) being disposed about an exterior of the elongate member (<NUM>), wherein the first monitor lumen (<NUM>) and the interior chamber of the first pressure-compliant member (<NUM>) define a fluid column,
characterized in that the first monitor lumen (<NUM>) has a volume of <NUM> microliters to <NUM> microliters; and the pressure sensing catheter (<NUM>) further comprises:
a connector apparatus (<NUM>) disposed about the proximal end and in fluid communication with the first monitor lumen (<NUM>), the connector apparatus comprising a first complementary connector (<NUM>) and a second complementary connector (<NUM>), the first complementary connector (<NUM>) and the second complementary connector (<NUM>) being connectable to each other in a complementary fashion, at least one of the first complementary connector and the second complementary connector (<NUM>, <NUM>) being fluidly coupled to the fluid column,
one of the first complementary connector and the second complementary connector (<NUM>, <NUM>) comprising a pressurizing device (<NUM>) and the other of the first complementary connector and the second complementary connector (<NUM>, <NUM>) comprising a bore (<NUM>, <NUM>),
wherein coupling the first complementary connector and the second complementary connector causes the pressurizing device (<NUM>) to displace a volume of fluid located within the bore (<NUM>, <NUM>) into the fluid column, wherein a ratio of a volume of displaced fluid to the volume of the fluid column is at least about <NUM>:<NUM> and less than about <NUM>:<NUM>.