Abstract: A transmitter unit with an attachable energy source is provided for a sensor guidewire. The transmitter unit is adapted to be connected to a proximal end of a sensor guidewire provided, at its distal end, with a sensor to measure a physiological parameter inside a patient. In some embodiments, the transmitter unit is adapted to wirelessly communicate by a communication signal with a communication unit, arranged in connection with an external device, in order to transfer measured physiological data to the external device. The attachable energy source can be a battery pack or battery holder provided with connecting electrical connecting surfaces. Preferably, the connection is protected from penetrating fluids by a protective seal.

Abstract: A system and method for measuring fluid flow and pressure in a flexible conduit is disclosed. An embodiment of the system and method uses an ultrasound sensor for determining volume of flow and a tonometric system for determining pressure along a common length of a flexible conduit.

Abstract: An apparatus for sensing multiple parameters includes an implantable housing and a plurality of implantable sensors disposed within the implantable housing. The plurality of implantable sensors sense parameters in a patient, such as biological or physiological parameters, for example, and each responds to an analyte in the patient. The plurality of implantable sensors may include, but is not limited to, electrochemical, potentiometric, current and optical sensors.

Abstract: Disclosed are systems and methods for enabling the acquisition of physiological parameters of a mammal or other specimen using thermo-mechanical responses (e.g., temperature, pressure and alternatively acceleration, pulse, position). In accordance with one example embodiment, a monitoring device for wired and/or wireless sensors is used to acquire a series of sensor signals that are attached to achieve the physiological measurements of a mammal vital signs is provided. The device includes a Temperature-Pressure (T-P) sensor configured to attach to respiration, vascular pressure and audio points of the mammal in a manner suitable for obtaining the acquired individual sensor electrical signal. The sensor system is configured to attach to alternative locations of the specimen in a manner suitable for obtaining electrical signals in communication with a signal receiver and transmitter. Physiological parameters, such as those associated with vital signs (temperature, pulse, respiration, etc.

Abstract: Techniques for estimating a cardiac chamber or vascular pressure based upon impedance are described. A device or system may measure an impedance between at least two electrodes implanted within or proximate to a cardiovascular system. The device or system may estimate a pressure of an element of the cardiovascular system based on a relationship between impedance and volume of the element, and based on a empirical relationship between the volume and the pressure. The device or system may also estimate the dimension of the element based on the impedance-volume relationship, or other characteristics based on the impedance. Because the impedance measurements may be obtained, in some examples, by using electrodes and leads implanted within the cardiovascular system and coupled to an implantable medical device, a practical estimation of a cardiovascular pressure can be obtained on a chronic basis without requiring the use other invasive sensors, such as micronanometer transducers.

Abstract: A lacrimal drainage manometer includes a syringe having a syringe body and a piston. The syringe body defines a fluid cavity in fluid communication with a cannula configured for insertion into at least a portion of a lacrimal drainage system. The piston dispenses a fluid from the fluid cavity through the cannula. A pressure sensor is operably coupled to the syringe for measuring fluid pressure in the fluid cavity. A position sensor operably coupled to the syringe measures the position of the piston relative to the syringe body. A user feedback unit in electrical communication with the pressure sensor and the position sensor provides user feedback based on data from at least one of the pressure sensor and the position sensor indicative of a condition of the lacrimal drainage system.

Abstract: A method and apparatus for continuously measuring the absolute intracranial pressure in a non-invasive manner is described by using an ultrasonic Doppler device which detects the pulsatility indexes of the blood flow inside the eye artery for both intracranial and extracranial eye artery portions. The eye in which the blood flow is monitored is subjected to a small pressure, sufficient to equalize the pulsatility index measurements of the internal and external portions of the eye artery. The pressure at which such equalization occurs is used as a reference for autocalibration of the apparatus so that continuous absolute intracranial pressure measurements may be taken over a particular sampling period.

Abstract: Methods and structures for detecting a physiologic parameter of a target anatomical environment. The device including a housing with a distal portion first port couplable to a probe and a proximal portion; and a sensing unit, a processing unit, and an output unit carried by the housing, the output unit configured to output a reporting signal based on the determined physiologic parameter value such as pressure; the sensing unit, processing unit, and output unit being disposed substantially between the first port and the proximal portion of the housing.

Abstract: An implantable device system is disclosed. The implantable device system comprises, a first energy transceiver system, a second energy transceiver system at least partially implanted within an organic tissue and capable of being interrogated by the first energy transceiver system, and a sensing system, wherein a state of the sensing system is available at the second energy transceiver system.

Abstract: An implantable polymer-based pressure sensor featuring an electrical LC-tank resonant circuit for passive wireless sensing without power consumption on the implanted site. The sensor is microfabricated with parylene to create a flexible coil substrate that can be folded for smaller physical form factor during implantation, and can be stretched back without damage for enhanced inductive sensor-reader coil coupling. Data received from the sensor can be enhanced to provide improved pressure measurements at increased distances.

Abstract: A transducer interface system/method allowing conversion from an analog sensor input to a standardized analog output interface is disclosed. In some preferred embodiments the system/method permits a fiber optic pressure sensor to be interfaced to a standard patient care monitor (PCM) system using standardized Wheatstone Bridge analog interface inputs. Within this context the Wheatstone Bridge sensed output is defined by stimulus from the PCM and modulation of bridge element values by the conditioned output of an analog pressure sensor. The use of analog-to-digital-to-analog conversion in this transducer interface permits retrofitting of PCM devices having analog Wheatstone Bridge inputs with advanced patient monitoring sensors without the need for specialized modifications to the baseline PCM data collection framework. Methods disclosed herein include techniques to connect arbitrary types/numbers of analog sensors to traditional PCM systems without the need for PCM system hardware/software modifications.

Abstract: Described herein is a device for glaucoma treatment and monitoring that comprises a combination of an intraocular pressure (IOP) sensor and a glaucoma drainage device. The device comprises an IOP sensor and an inductive antenna mounted within a porous biocompatible material that forms the drainage path. The IOP sensor is mounted in a footplate portion of the device and is mountable in the anterior chamber of an eye. The footplate portion is connected to a body portion that houses the spiral antenna by a neck portion which retains the footplate portion in a suitable position within the anterior chamber. Due to its size, the footplate portion housing the IOP sensor can readily be inserted into the anterior chamber with the body portion housing the spiral antenna located outside of the anterior chamber in a sub-scleral space to disperse the aqueous humour.

Abstract: An anti-fouling sleeve for an endotracheal tube, a method of placement, and the tools for placement. The anti-fouling sleeve occupies the entire length of endotracheal tube, and can be installed permanently or made removable and disposable. The sleeve may be instrumented with sensors and/or a UV light source to reduce and potentially eliminate biofilm formation. Once placed inside the endotracheal tube the sleeve expands to conform to the inner diameter of the tube. After use, any accumulated biofilm on the inner portion of the sleeve is removed leaving the inner portion of the endotracheal tube essentially sterile.

Abstract: An implantable pressure sensor arrangement is disclosed. The arrangement includes a substrate, a coil positioned on the substrate, a flexible membrane positioned proximate to the coil and configured to be moveable with respect to the coil, thereby forming a fluid chamber, fluidly sealed from outside of the implantable pressure sensor arrangement, a porous membrane positioned on the flexible membrane and configured to transfer pressure from outside of the implantable pressure sensor arrangement onto the flexible membrane wherein a differential pressure is generated on the two sides of the flexible membrane thereby causing the flexible membrane to deflect towards and away from the coil, and an electrode coupled to the flexible membrane.

Abstract: The present invention relates to a probe and a device for detecting abnormality of an intervertebral disc. More particularly, the present invention relates to a probe and a device for detecting abnormality of an intervertebral disc that gives vibration stimulation to the inner part of the intervertebral disc and obtains an ultrasonic image in order to sense the abnormality of the intervertebral disc causing discogenic pains and inspects whether the intervertebral disc is abnormal by measuring impedance in the intervertebral disc. The present invention provides a probe for detecting abnormality of an intervertebral disc including: a shaft connector; a vibration generator connected to the shaft connector; and an inspector connected to the vibration generator, wherein the vibration generator vibrates the inspector by using a piezoelectric element and a device for detecting abnormality of an intervertebral disc.

Abstract: A pressure measuring device for measuring the internal pressure of the affected part under the fixing member includes a plurality of flexible pressure meters (or called as manometers) and a processor connected to each of the flexible pressure meters. The flexible pressure meters are configured at the inner surface of the fixing member and pasted on the affected part to measure the surface pressure of the affected part, and generate measuring signals according to the measured pressure. The processor is capable of receiving the measuring signals and displaying the surface pressure of the affected part according to the measuring signals, furthermore, by analyzing the measuring signals, the internal pressure corresponded to each of the compartments of the affected part can be found. Accordingly, the pressure measuring device assists to judge if compartment syndrome occurs in the affected part.

Abstract: An apparatus and method are provided for use in studying a patient's bowel which combines recording and analysis of physiologic parameters and patient sensory perception. A pain input detector, a pain transducer, and a processor are provided. A gas pressure transducer and flow meter may also be provided. Output data may be generated to reflect perceived patient pain, volume of gas delivered to the patient's bowel, and bowel pressure. An indication of perceived patient pain is processed by the processor to generate data that may used to validate a scan of a patient or may be used as a diagnostic tool.

Abstract: Parameters extracted from high definition manometric measurements of the pharynx and upper esophagus at preidentified locations and times are applied to a supervised learning machine trained using x-ray fluoroscopy data to provide diagnostic information comparable to that of x-ray fluoroscopy without radiation exposure.

Abstract: A system and methods that provide for visualization and/or characterization of manometry data. Visual representations of pressure information represent pressure information measured over time by sensors positioned within an organism. Markers may be provided on the visual representations. Using the system and methods described herein, various characteristics of an organism and/or events that occur within the organism may be determined.

Abstract: An air management system is described for removing and reintroducing a desired amount of air into an air passage of a pressure measurement catheter. More specifically, the system includes a cylindrical housing, check valves in communication with the housing and an moveable shaft with multiple sealing members along its length. As the shaft is moved within the housing, a piston member causes the residual air in the catheter air passage to be evacuated to a defined negative pressure. Further movement of the shaft causes a piston member to inject a predetermined volume of air into the catheter air passage. In this respect, periodic adjustments of the piston member returns the volume of air in a variable volume chamber to one that is unaffected by residual volume in the chamber and that provides an optimum volume of air to maximize the time the sensor can function accurately between recharging events.

Abstract: Apparatus (20) is provided for use in a gastrointestinal tract (40) of a patient, including an inflatable device (22) configured to be moved through the gastrointestinal tract (40) to a treatment site in response to a difference between fluid pressure proximal to the inflatable device (22) and fluid pressure distal to the inflatable device (22). An optical system (24) coupled to the inflatable device (22) configured to image the gastrointestinal tract (40). A working channel (32) coupled to the inflatable device (22) and shaped to define a channel lumen therein to provide access from outside of the patient to the treatment site. A tool (34) configured to be passed through the channel lumen and to emerge from a distal end of the working channel (32). The tool (34) comprises a tool steering mechanism (44) to facilitate steering of the tool (34) from outside of the patient. Other embodiments are also described.

Abstract: Devices, computer readable programs and methods determine a patient parameter, including volume and/or flow rate of a fluid draining through a drain tube from a chest cavity of a patient, by using at least one pressure value at an end of the drain tube associated with a fluid collection canister and at least one pressure value within the drain tube at a location distant from the collection canister. The pressure values are processed with a non-linear solver to determine the patient parameter.

Abstract: A ventricular shunt systems and methods of preventing hydrocephalus are described herein. In one aspect, the ventricular shunt system has at least one pressure sensor that is configured to be selectively electromagnetically coupled to an ex-vivo source of RF energy and is variable in response to the pressure in a patient's ventricle.

Abstract: Devices and methods useful for non-invasively measuring and indicating a rate of fluid flow are disclosed. In one embodiment, a sensor housing adapted to received fluid flow therethrough is provided. A radio frequency tag and a masking element can be disposed in the sensor housing. The masking element and the radio frequency tag can be configured to move relative to one another. The relative positions or movement can alter the response of the radio frequency tag to a wireless signal (which can be emitted from an external reading device, for example) and thereby indicate a rate of fluid flowing through the housing. For example, in some embodiments, the masking element can selectively cover at least part of the radio frequency tag in correspondence to the flow rate, which can change a characteristic of the radio frequency tag's response to the wireless signal.

Abstract: A probe (1) for enteral nutrition includes a tubular element (2) of elongated shape and flexible, with a first extremity (2a) having a supply mouth (4) for the introduction of nutritional substances or the like and a second extremity (2b) positionable inside the stomach of a patient and having at least a dispensing hole (6) for dispensing the nutritional substances, the tubular element (2) having a main channel (7) of communication between the supply mouth (4) and the dispensing hole (6). The probe (1) includes at least a first and a second reading element (8, 9) for reading the pressure inside the digestive system of the patient at two distinct sections of the tubular element (2).

Abstract: The present invention relates to the diagnosis and treatment of urinary incontinence. The diagnosis and treatment involves the use of a multiple sensor-enabled catheter capable of providing real-time data regarding the patient's physiology, such as urinary flow and muscular function of the bladder of the bladder sphincter, as well as the position and movement of the catheter within the patient.

Abstract: Measurement of a patient's leak point pressure in the bladder can be taken by a processor in communication with a pressure catheter in the bladder. When leakage occurs pressure data points can be recorded. In some embodiments, the peak pressure can be determined based on pressure data points measured during a set time just before receiving a clinician input indicative that leakage has occurred.

Abstract: A method is provided for internally monitoring pressure of a patient by transmitting an external light source to an implantable microsensor device. The implantable microsensor device has a microlens, a deflectable membrane responsive to a change in pressure of a surrounding environment within the patient, and an array structure disposed between the microlens and the membrane. The array structure includes a first layer that emits a first wavelength of light and a second layer that emits a second wavelength of light responsive to an external light source, where the first and second wavelengths of light are respectively transmissive through the surrounding environment and distinct from one another. Either the array structure or the microlens translates with the membrane in response to the change in pressure of the surrounding environment. The implantable microsensor is compatible with medical imaging devices and does not require an internal or external power supply.

Abstract: An implantable restriction device is configured to provide a restriction in a patient. A pressure sensor implanted in the patient is configured to sense pressure associated with the restriction device. A remote input device is configured to wirelessly receive pressure measurements from the pressure sensor and transmit the pressure measurements to a display device. The display device is configured to plot the pressure measurements as a function of time. The remote input device also includes buttons that may be used to annotate the pressure measurements, such as to indicate physical events associated with the patient (e.g., coughing, sneezing, etc.). The display device is also configured to display the annotations on or near the plot of pressure measurements. A viewer may thus take the annotations into account when evaluating the pressure measurements, such as by ignoring pressure measurements associated with certain types of annotations.

Abstract: In an implantable pressure measuring device, in particular for measuring an intracranial pressure, is provided. In order to simplify production, it is proposed that the pressure measuring device comprises an implant housing and a pressure measuring sensor, which is arranged in the implant housing, with one or more load cell(s). The implant housing has an opening. The pressure measuring sensor is provided with a coating applied directly to the load cell(s). The pressure measuring sensor is arranged in the implant housing in such a way that the opening provides direct access to the load cell(s) for a fluid surrounding the pressure measuring device and therefore the surrounding pressure acts directly on the coated load cell(s) of the pressure measuring sensor. The coating is produced from a para-xylylene-based polymer material.

Abstract: Certain pressure sensor devices are much smaller than prior art devices, yet are at least as sensitive as the prior art devices. A capacitive pressure sensor can include a flexible substrate that permits bending of a pressure sensing region without significantly affecting operation thereof. The pressure sensor can include a flexible membrane in which an electrode is sandwiched between two layers of polymeric material. The sandwiched electrode can be extremely close to a reference electrode so as to provide for highly sensitive capacitance readings, yet the membrane can be restricted from contacting the reference electrode under high pressure conditions.

Abstract: A ventricular shunt systems and methods of preventing hydrocephalus are described herein. In one aspect, the ventricular shunt system has at least one pressure sensor that is configured to be selectively electromagnetically coupled to an ex-vivo source of RF energy and is variable in response to the pressure in a patient's ventricle.

Abstract: Provided are devices and methods suitable for immobilizing tissue and for use in non-invasive methods of assessing lower urinary tract symptoms as well as in surgical application.

Abstract: A pressure sensing catheter may include an elongate tubular catheter body having a first lumen extending longitudinally within the catheter body, and a second lumen extending longitudinally within the catheter body adjacent to the first lumen. Each of the first and second lumens may include proximal and distal end openings positioned at proximal and distal ends, respectively, of the catheter body. A tip portion may extend distally from the distal end of the catheter body and may include an outer wall and a tip lumen. The tip lumen may include a first and second end openings coupled to the distal end openings of the first and second lumens, respectively. The first lumen and the second lumen may be in fluid communication with one another through the tip lumen. The tip portion may be deformable in response to an external pressure applied to the outer wall of the tip portion.

Abstract: A resuscitator has a patient airway interface device, a bag, a flow passage coupled between the bag and patient airway interface device, and a sensor assembly. The patient airway interface device may be a mask or an endotracheal tube. The sensor assembly has a display, at least one sensor coupled to the flow passage and configured to provide a measurement of at least one parameter, and a processor coupled to the display and the at least one sensor. The processor is configured to receive the measurement from the sensor and provide information on the display based on the received measurement. The information may include a current breath rate, a pressure-vs-time curve, and guidance to the user to assist in achieving a target breath rate.

Abstract: A device and method for measuring the structural integrity and structural health of the female pelvic floor, or other lumenal organ, is disclosed. Said device comprises an insertable probe with a pressure chamber capable of distending the walls of said lumenal organ. The invention also comprises means for positioning the pressure chamber and adjusting its location along the lumen. Said device also comprises means for changing and recording the volume and pressure of a balloon which is part of the pressure chamber, and means for determining and recording the location of the walls of the balloon. Said device also comprises a means for integrating information obtained to determine important biomechanical information, such as stress-strain curves, which a medical clinician can use for diagnostic purposes. Said method comprises the insertion of said probe, the expansion and contraction of the pressure chamber under desired condition, and means for analyzing obtained data for increased usefulness to the clinician.

Abstract: The systems, devices, and methods described herein provide for the estimation and monitoring of cerebrovascular system properties and intracranial pressure (ICP) from one or more measurements or measured signals. These measured signals may include central or peripheral arterial blood pressure (ABP), and cerebral blood flow (CBF) or cerebral blood flow velocity (CBFV). The measured signals may be acquired noninvasively or minimally-invasively. The measured signals may be used to estimate parameters and variables of a computational model that is representative of the physiological relationships among the cerebral flows and pressures. The computational model may include at least one resistive element, at least one compliance element, and a representation of ICP.

Abstract: Systems and methods are described for noninvasively assessing an intracranial pressure of a patient. Some embodiments include providing a simulation model with a measured arterial blood pressure of the patient. Some embodiments further include providing the simulation model with a measured cerebral blood flow velocity of the patient. The simulation model correlates arterial blood pressure values, cerebral blood flow velocity values, and intracranial pressure values. Some embodiments further includes determining an intracranial pressure of the patient based on the simulation model. Some embodiments further includes creating an output data set indicative of the determined intracranial pressure.

Abstract: A hermetically sealed biocompatible pressure sensor module configured for implant at a desired site at which a pressure is to be measured. Anodic bonding of the pressure module package components which have similar thermal coefficients of expansion provides low stress bonding and maintains long term reliability, dependability and accuracy. The pressure sensor module includes a pressure sensitive membrane which is in direct contact with the environment at which a pressure is to be measured. The pressure sensor module forms a part of a pressure measuring system which uses a telemetry link between the pressure sensor module and an external controller for data transmission and transfer. Operating power for the pressure sensor module is provided by the external controller and an internal rechargeable energy storage component. Accordingly, the pressure measuring system provides a dual stage power and data transfer capability for use with an implantable system.

Abstract: Embodiments of the invention provide such an improved system and method. In particular, embodiments relate to systems, methods and apparatuses which use acoustic data in the detection of coronary artery disease. Embodiments can enable fast, non-invasive identification of clinically relevant coronary artery disease, which can ultimately save lives. The non-invasive nature is one example of a multitude of convenient aspects of embodiments that can be used to meet a large, as yet unmet need in a cost-effective and accurate manner. Results can be provided in real-time and with clarity, providing quick and easily understandable indications that can shorten the path to intervention for patients, making embodiments suitable for a wide range of environments, purposes, users and patients.

Abstract: Methods and devices for detecting positioning of a probe in a tissue of a patient. A method can include providing a detection device; advancing a device coupled probe through the tissue of the patient and toward the patient's spinal canal; detecting a change in pressure about the distal portion of the coupled probe during advancing, where the detected pressure change indicates probe positioning in the patient's spinal canal; outputting the detected pressure change or indication of probe positioning to a visual display.

Abstract: A device comprising a kit and a method for using the kit are disclosed that warn a surgeon that the maximal grafting capacity of a recipient tissue has been reached. The increase in interstitial pressure is measured at the recipient site using any of several pressure sensor devices during the grafting process to alert the surgeon to stop grafting once a critical level has been reached, or a sudden increase in pressure is detected, indicative of a maximum graft size.

Abstract: A nasogastric/orogastric (Ng/Og) device includes a main lumen configured for at least one of gastric decompression, enteral feeding and enteral medication administration. An expandable esophageal cuff is carried by the device body and configured in a normally expanded position such that when inserted within the esophagus, the esophageal cuff conforms to the interior surface of the esophagus and emesis and/or reflux is blocked from passing out of the stomach and past the esophageal cuff. A vacuum lumen is carried by the device body and connected to the expandable esophageal cuff. When vacuum is applied, the esophageal cuff is contracted against the device body to permit the device to be inserted and placed within the esophagus. When the vacuum is released, the esophageal cuff expands against the interior surface of the esophagus.

Abstract: Measurement device and method for noninvasive determination of at least one physiological parameter, the device comprising a diagnostic sensor unit (1) for generating measurement signals, and an evaluation unit for processing the measurement signals. The diagnostic sensor unit (1) comprises at least one pressure sensor (3) which detects the pressure exerted locally onto the pressure sensor (3) by a body tissue which is to be examined. The evaluation unit is configured to derive at least one physiological parameter from the measurement signal of the pressure sensor (3).

Abstract: Improved wiring arrangements for sensor catheters are provided to reduce wire-to-wire cross-talk wherein wires connecting the sensor of the sensor catheter to a processing unit are divided into a plurality of wire bundles contained within respective sheaths, with the wires in wire bundle twisted together reduce electromagnetic signal interference among the individual wires, or between wire bundles.

Abstract: A system and methods that provide for visualization and/or characterization of manometry data. Visual representations of pressure information represent pressure information measured over time by sensors positioned within an organism. Markers may be provided on the visual representations. Using the system and methods described herein, various characteristics of an organism and/or events that occur within the organism may be determined.

Abstract: An arthroscopic surgery sheath system having: a body for insertion of an instrument; an insertion portion coupled to the body; a valve coupled to the insertion portion; a tube coupled to the valve; and a microelectromechanical sensor positioned inside the valve or the tube for measurement of at least one characteristic of a fluid inside of the tube; wherein the sensor is configured to transmit measurement information.

Abstract: The present invention relates to a method and a device for determining the hydro-dynamic properties of the fluid system surrounding the brain and the spinal cord, the so called cerebrospinal fluid system, whereby the method comprises continuous pressure measurement through a fluid contact passage and active infusion of artificial cerebrospinal fluid through another fluid contact passage to a number of pressure-flow levels, and analysis of the connections between the measured pressures and flows. The method uses an adaptive way of procedure which on each pressure-flow level takes account for the measure time and the patient's fluctuations in physiologic signals for calculating in real time when the relation between the measure time and measure accuracy in pressure and flow on the actual pressure-flow level is sufficient and at an optimum, whereupon the investigation or examination is automatically proceeding to the next level according to a predetermined protocol.

Abstract: A system for measuring and converting to an observer intelligible form an internal physiological parameter of a patient. The invention allows transcutaneous telemetry of intracranial pressure via a system which includes a patient implanted sensor module and an external processing module, optically coupled to the sensor module via an external coupling module. A sensor within the sensor module transduces the measured pressure and a near infrared emitter transmits the telemetry when interrogated by the external coupling module. A set of tuned inductor-crystal circuits comprised in part of a cylindrical crystal oscillator whose resonant frequency is sensed by a dipper circuit arrangement is provided. Power for the sensor module is derived inductively through rectification of a transcutaneously-applied high-frequency alternating electromagnetic field generated within the external coupling module.

Abstract: Methods and devices for measuring the size of a body lumen and a method for ablating tissue that uses the measurement to normalize delivery of ablational energy from an expandable operative element to a luminal target of varying circumference are provided. The method includes inserting into the lumen an expandable operative element having circuitry with resistivity or inductance that varies according to the circumference of the operative element, varying the expansion of the operative element with an expansion medium, measuring the resistivity of the circuitry, and relating the resistivity or inductance to a value for the circumference of the operative element. In some embodiments the sizing circuit includes a conductive elastomer wrapped around the operative element.