US20210330349A1 - Device and Method for Needle/Catheter Location Utilizing Correlation Analysis - Google Patents

Abstract

An apparatus and method to enable clinicians to verify needle or catheter location within an anatomic site by relying upon combined sensing of two signals, such as a pressure signal and a heart rate pulse signal, in which the detection of a correlation between both signals is identified to confirm location of the needle or catheter.

Description

FIELD OF THE INVENTION
• The present invention relates generally to devices and methods for determining needle or catheter location in a patient utilizing a correlation analysis, and more particularly, but not exclusively, to correlation analysis, such as comparison of beats-per-minute or cross-correlation of waveforms, of objective pressure in the needle or catheter and the patient's heart rate pulse.
BACKGROUND OF THE INVENTION
• Currently, when measuring pressure within a needle or catheter, there is no ability to identify false-positives of a cardiac pulsewave detected in the needle or catheter as opposed to pressure changes which truly represent the cardiac pulsewave. As used herein cardiac pulsewave is defined to mean a pressure waveform which contains a signal which originates from the contraction of the heart or vessels, and therefore contains information representing, the cardiac pulse. It is conceivable that a needle or an indwelling catheter can detect a non-cardiac pulsation from a variety of non-cardiac sources within the body, including respiratory changes, muscle movements of the diaphragm, etc, and can falsely report that detected pulsation as the cardiac pulsewave. It is also conceivable that patient bodily movements, such as postural changes in position of the patient, could produce pressure changes that are measured and are misinterpreted as originating from the cardiovascular system. In particular, existing devices do not include an independent means to verify that a particular pressure waveform is from the heart, and thus cannot rule out false positives in which the detected waveform has come from a source other than the cardiovascular system. At the same time, determining the location or the patency of a needle or catheter is of great interest to the clinician, such as for delivering of a drug to a patient. Hence, the ability to ensure that the pressure being sensed is not confused with other pressure changing waves produced in the body is of great interest if one is to rely on this information as indicative of needle or catheter placement, which, in turn, will impact patient outcome.
• For example, in clinical use, after the placement of a needle or catheter it is common to deliver a dose of medication. Subsequent administrations through a needle or catheter can be compromised due to potential blockage of the needle or catheter, or by migration of a needle or catheter from the original position. Therefore, catheter assessments may be required including determining if a catheter is clogged, determining if the catheter is fully functional, and determining if the catheter has moved from the initial location. The inability to accurately differentiate a catheter's function leaves the clinician in a serious and sometime dangerous quandary: is the failure due to effectiveness of the drug, movement of the catheter, a clogged catheter from precipitate or a blood clot?
• The data also show that between 10 to 25% of all catheters need to be replaced on patients because of catheter migration after placement. Clinicians have difficulty determining the reason for the failure of a catheter. Typically it takes to 20 to 30 minutes to evaluate catheter function and placement as the clinician waits for an observation to a therapeutic drug response, because currently this is the only means to evaluate catheter function. This adds additional risks and additional costs to healthcare systems, as a non-functional catheter can require life-threatening time to assess. Thus, the difficulties and potential risks of catheter placement and monitoring are serious challenges, and therefore a predictable manner to differentiate these conditions would be of great value to patients and clinicians.
• Even so, existing devices developed to detect pulsatile waveforms can be expensive and complicated to use, requiring the use of an electro-mechanical motor to deliver the fluid to the patient. Such devices do not allow a clinician to observe an objective pressure generated while manually infusing a drug using a handheld syringe as is typically or preferably done. Existing systems are also not designed with inputs from multiple sources to separately compare and analyze both a heart-beat and pulsatile pressure waveform during use, and so do not provide two distinct physiologic sources of heart rate to determine and verify needle or catheter location. As such, the inventors, in arriving at the present invention, have recognized deficiencies in prior art devices and methods for needle or catheter placement, such as the ability to: 1) detect an input source of a cardiovascular system in which the heart-rate is used for direct comparison with needle or catheter location; 2) detect a cardiovascular response via a direct fluid path and analyze the information in the fluid path to produce beats-per-minute analyses to compare to a secondary source which is known to be detecting a heartbeat; 3) correlate and analyze more than one signal to determine that a needle or catheter is properly placed within an anatomic location; and 4) to provide a positive alert when these two signals are correlated within a range to confirm a true-positive.
• Therefore, there is a need in the art for inexpensive and simple devices and methods that are capable of eliminating false-positives when locating a needle or catheter in the body which devices and methods would be of great value to the clinician and to the treatment of patients.
SUMMARY OF THE INVENTION
• In view of the above-noted and other needs, in one of its aspects the present invention may provide devices and methods which use two or more different physiologic sources indicative of the cardiac pulse to determine needle or catheter placement prior to medication delivery or fluid aspiration. One of the sources may be the cardiac pulsewave detected as a pressure waveform in the needle or catheter, such as by an in-line pressure sensor, and a second source may be heartbeat detection from a finger pulse sensor, for example, or other location known to emit the cardiac pulsewave or heartbeat. The two physiologic sources may then be compared to verify that the pressure waveform detected in the needle or catheter is in fact the cardiac pulsewave, thus eliminating false-positive indications of the cardiac pulsewave in the needle or catheter. The comparison may be performed as a correlation analysis of signals from the two different physiologic sources to determine if the frequency of the signals from the two different physiologic sources is clinically comparable. The correlation analysis may be performed as a comparison of the numerical value of heart rate in beats-per-minute as detected at each of the two or more different physiological sources and/or by cross-correlation of waveforms detected at each of the two or more different physiological sources, for example. Thus, the present invention can perform “Needle/Catheter Location Correlation Analysis” as a comparison of two or more cardiovascular signals which may include beats-per-minute, cross-correlation of pressure waveforms, and/or objective pressure measurements, for example, to determine the location of a needle or a catheter within a mammalian body.
• Positive verification of the cardiac pulsewave in the needle or catheter may establish both the correct position of the needle or catheter and its patency. As a result, devices and methods of the present invention can allow clinicians to more easily assess in real-time proper needle or catheter placement with confidence, due to the verified detection of the cardiac pulsewave. These may be presented to the clinician as a signal or an alert confirming proper needle or catheter placement. As a result, with the verified real-time detection of the cardiac pulsewave in the needle or catheter the clinician may use a manual syringe rather than an automated mechanical pump such that the clinician can personally position the needle and control the delivery of medication or aspiration of fluid and the accompanying physical force applied to the syringe. More precise control of the physical force by the clinician can also prevent catheter movement from excessive pressures. Excessive pressure during medication delivery could cause the dislodgement of the needle or catheter from a site as uncontrolled fluid pressures produce a “jet-stream” at the tip of the catheter or needle.
• In another of its aspects, devices of the present invention may provide a clinician with an objective (i.e. measured) pressure value in the needle or catheter during the flushing stage. Knowing the objective pressure as a medication is injected can also assist the clinician in avoiding excessive force, preventing excessive pressures. For example, the present invention may alert the clinician when a pressure value has been exceeded. The alert can be audible, visual, haptic or the like.
• Exemplary uses of devices and methods of the present invention may include locating a needle within the body to a specific target site, such as that of an epidural procedure or peripheral nerve block. In particular the identification of the epidural space, the determination of needle proximity to a neurovascular bundle in regional peripheral nerve blocks, and other medical procedures which require a needle or catheter tip to be positioned at a specific location (e.g., intrathecal, intravenous, intra-arterial, organ of the body) where the cardiac pulse is present, all can benefit from devices and methods of the present invention. Accordingly, the use of devices and methods of the present invention at such exemplary target sites can with greater reliability replace the current Loss-of-Resistance technique (LOR-technique). Further to its advantages, devices and methods of the present invention may be used for all types of needles and catheters that are placed into patients at anatomic sites at locations that emit a rhythmic pulsation of the arterial system, and may be provided as an inexpensive and portable system.
• In still further of its aspects the present invention may achieve a number of objectives. For example, an objective of the invention may be to detect a pulsatile waveform of a catheter which is verified for the presence of a cardiovascular pulse by comparing a first input to a second input from the cardiovascular system, such as a heartbeat detected from a second input source. The redundant nature of these two sources may be identified and confirmed electronically and produce an alert to the operator. A further objective of the present invention may be to provide an inexpensive device to determine an objective pressure value that is generated when a drug is injected through a catheter using a manual syringe to prevent excessive pressure production at the tip of a catheter that might dislodge the catheter from a target position. Devices of the present invention can enable an audible alert to be set for a maximum pressure value to alert the operator if they have exceeded a specific pressure value. In addition, a further objective may be to detect and display a pulsatile pressure waveform corresponding to the pulse of the cardiac-vascular system to determine the position of a catheter. A further objective of the invention may be to provide a method and device that can detect the pulsatile pressure waveform that is present in the epidural space or intrathecal space of the central nervous system and detecting a pulsatile waveform or the proximity to the neurovascular bundle of nerve. A further objective may be to observe an objective pressure and graph an objective pressure value over time to monitor the response to an injection performed with a manual syringe to determine the patency of a catheter. Another objective may be to correlate an objective pressure value with a pulsatile pressure waveform to determine the patency and position of a catheter by simultaneously viewing the pressure/time graph and the pulsatile pressure waveform to determine catheter function. A further objective may be to provide a mean value of a pulsatile pressure waveform from an intravenous catheter to determine the patency of said catheter before, after and during an infusion.
• In particular, in a first exemplary configuration, the present invention may provide an apparatus for confirming placement of a hollow-bore structure at a desired treatment location in a mammalian subject. The apparatus may include a first sensor operably connected to a lumen disposed in the hollow-bore structure; the first sensor may be configured to provide a first signal in response to detection of a first property indicative of a cardiac pulse in the lumen of the hollow-bore structure. The apparatus may include a second sensor configured to provide a second signal in response to detection of a second property indicative of the cardiac pulse. A controller may be operably connected (wireles sly or wired) to the first and second sensors to receive the first and second signals, and maybe configured to compare the first and second signals to provide a comparison result, whereby the comparison result provides an indication of placement of the hollow-bore structure relative to the desired treatment location. The first and/or second physical property may be one or more of a pressure, change in fluid volume, an electrical signal, and an optical signal. The first and second properties may relate to the same physical property or different physical properties indicative of the cardiac pulse. The hollow-bore structure may include one or more of a needle and a catheter. The first sensor may include an in-line pressure sensor having a sensor lumen disposed in fluid communication with the lumen of the hollow-bore structure, and the second sensor may be a finger pulse sensor. One or more of the first and second sensors may include a memory configured to store an indication that the first or second sensor, respectively, has been used. The device may also include an identification circuit embedded within or connected to one or more of the first and second sensors, wherein the identification circuit is configured to provide a signal to the controller, the signal including one or more of: a configuration signal indicative of physical characteristics of the first or second sensor; a verification signal indicative of the first or second sensor; and a use signal so that the controller can detect the number of times or length of time the first or second sensor was previously used.
• In a second exemplary configuration the present invention may provide an apparatus for confirming placement of a hollow-bore structure at a desired treatment location in a mammalian subject having a controller configured to receive a first signal from a first detector placed at the treatment location. The first signal may be indicative of a cardiac pulse in the hollow-bore structure. The controller may also be configured to receive a second signal indicative of the cardiac pulse from a second detector placed at a second location. The controller may be programmed to compare the first and second signals to provide a comparison result, whereby the comparison result provides an indication of the placement of the hollow-bore structure relative to the desired treatment location.
• For both the first and second (or other) exemplary configurations, the first and/or second signal may represent one or more of a pressure, change in fluid volume, an electrical signal, and an optical signal. The first signal may have a first period and the second signal may have a second period, and the controller may be configured to compare the first and second periods to provide the comparison result. (In addition, the first signal may include a waveform having a first period and the second signal may include a waveform having a second period, and the controller may be configured to compare the first and second periods to provide the comparison result.) Further, the first signal may include a first numeric value indicative of a frequency of the first signal, and the second signal may include a second numeric value indicative of a frequency of the second signal, and the controller may be configured to compare the first and second numeric values. One or more of the first and second numeric values may be a cardiac pulse in beats-per-minute. The controller may also be programmed to perform a cross-correlation analysis of the first and second signals. The controller may be configured to create an alert signal when the comparison result is within a selected value. In addition, a display may be operably connected to the controller for receiving one or more of the first and second signals and the comparison result from the controller. In one desirable configuration, the controller may include the display. The display may include a first data section for displaying a pressure detected by the first sensor in the lumen disposed in the hollow-bore structure, and may include a second data section for displaying the first and second signals. The first and second signals may each include a respective waveform, and the second data section may include a graph displaying the respective waveforms of the first and second signals. The display may also include a section for displaying an alert indication when the comparison result is within a selected value. The alert may be one or more of an auditory, visual, and haptic signal.
BRIEF DESCRIPTION OF THE DRAWINGS
• The foregoing summary and the following detailed description of exemplary embodiments of the present invention may be further understood when read in conjunction with the appended drawings, in which:
• FIG. 1 schematically illustrates an exemplary configuration of a device for needle or catheter location in accordance with the present invention in which both a controller and display device are used;
• FIG. 2 schematically illustrates a further exemplary configuration of a device in accordance with the present invention in which a separate controller is not used;
• FIG. 3 schematically illustrates additional aspects of the devices ofFIGS. 1 and 2;
• FIG. 4 schematically illustrates an exemplary configuration of a display of a prototype in accordance withFIG. 1 of the present invention, in which the display shows objective pressure over time and cardiac pulsewaves and pulse detected from two independent sources, along with numerical display in real-time of clinically useful parameters of objective pressure and the numerical pulse rates of each of the two independent sources, along with an indicator showing whether or not the two independent sources are correlated in frequency (i.e., that the two independent sources both relate to the cardiac pulse);
• FIG. 5 schematically illustrates details of an exemplary operation of the devices ofFIGS. 1-3;
• FIG. 6 illustrates a circuit diagram of an exemplary configuration of the controller ofFIG. 1;
• FIG. 7 illustrates a flow chart of an exemplary method of operating the device of the present invention;
• FIG. 8 illustrates a method for performing signal correlation in accordance with the present invention; and
• FIG. 9 illustrates a further method for performing signal correlation in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
• Referring now to the figures, wherein like elements are numbered alike throughout,FIGS. 1, 2 schematically illustrate exemplary configurations ofdevices100,150 of the present invention for determining proper placement of a hollow-bore structure, such as aneedle302 and/orcatheter310, at a selected treatment location in a patient20 using at least two independent measurements of the cardiac pulse, one of which measurements is detected via the hollow-bore structure. For example, the detection of the cardiac pulse via theneedle302 and/orcatheter310 may be accomplished by sensing a physical property in the lumen of theneedle302 and/orcatheter310, such as a physical property representing the pressure or fluid volume change in the lumen, where the variation in the pressure or fluid volume change contains a signal created by, and indicative of, the cardiac rhythmic contraction, e.g. the cardiac pulsewave. In particular, an in-line pressure sensor300 may be provided in fluid communication with, and between, the needle302 (or catheter310) and a manual,handheld syringe200,FIGS. 1, 2.
• The second of the two independent measurements may be detected by a second device, such as afinger pulse sensor400, disposed at a location on the patient20 at which a physical property representing the cardiac pulse may be detected,FIG. 2. The physical property may be a pressure, an electrical signal, an optical signal, or other suitable signal, for example, that provides for independent verification of the presence of the cardiac pulse detected in theneedle302 and/orcatheter310. The physiologic location of thesecond device400 may be different from that of theneedle302 and/orcatheter310.
• Through the use of twoindependent measurement sources300,400 for the cardiac pulse,devices100,150 of the present invention can compare the signals from the twoseparate sources300,400 to confirm that the signal from theneedle302 and/orcatheter310 is indeed the cardiac pulse, which in turn will confirm that theneedle302 and/orcatheter310 is in the “correct” location for procedures in which the target tissue is one in which the cardiac pulse is expected to be present. For example, target sites for correct needle or catheter placement in which the cardiac pulse is expected to be present include the epidural space, intrathecal space, or proximate to a neurovascular bundle or other anatomic structure that emits a pulsatile wave produced by the cardiovascular system, including the heart itself.
• Once confirmation of needle or catheter placement is confirmed by thedevice100,150, an alert may be provided to the clinician, and the clinician may proceed with injection or aspiration through thesyringe200, depending on the nature of the procedure being performed. The alert may be provided in any suitable form, such as auditory, visual, or haptic, for example. Thus, devices of the present invention are capable of location guidance and confirmation during the placement of aneedle302 and/orcatheter310. Indeed, devices and methods of the present invention may confirm patency of theneedle302 and/orcatheter310.
• Turning toFIG. 1 in more detail, operation of thesensors300,400 may be provided by adedicated controller device500. Thecontroller device500 may be operably connected to thesensors300,400 viarespective cables210,410, and in certain cases anadapter212 may be provided between thecontroller device500 and arespective cable210. Alternatively, thesensors300,400 may communicate wirelessly with thecontroller device500, via any suitable communications technology such as Bluetooth® communication. Thesensor300 disposed in sensing communication with theneedle302 and/orcatheter310 may, as described above, be an in-line pressure sensor whose fluid path is continuous with theneedle302 and/orcatheter310, such as a Merit Medical, MER200. In such a case, the contraction of the heart produces propagation of an energy wave representative of the cardiac pulse into a fluid in thesensor300 and the wave may be measured through pressure or volumetric changes therein. The changes may produce a repetitive signal in the form of a pulsewave signal and may be measured from peak-to-peak or zero crossings to determine the frequency of the pulsewave signal to yield the cardiac pulse rate in beats-per-minute. Alternatively, thesensor300 could be positioned alongside thecatheter310 and/or could be interposed between an external fluid source such as an IV bag, syringe or any vessel that provides a continuous fluid line.
• In addition, the sensor300 (and/or sensor400) may be one or more of an acoustic sensor, optical sensor, infrared detector or other device which detects the cardiac pulse which has propagated within tissues from the cardiovascular system to the location of thesensor300,400. In short, any sensor type capable of detecting the cardiac pulse in the lumen of theneedle302 and/orcatheter310, whether by pressure, sound, or other physical property, may be used as thesensor300. Similarly, any sensor type capable of detecting the cardiac pulse at a physiologic source independent of the lumen of theneedle302 and/orcatheter310 may be used as thesensor400 including one based on photophelthysmography (PPG) such as a Model 3231 USB or Model 3230 Bluetooth® Low Energy from Nonin® Medical, Inc, for example. Alternatively, thesensor400 may be provided as a pneumatic inflatable cuff (such as that found in a sphygmomanometer). With a preference for using non-invasive methods for detecting the heart beat or beats-per-minute of the peripheral vascular system, it is also possible that the detection of the heart beat could be from an electronic signal that is captured with a heart-rate monitor in contact with the skin of a patient.
• One or more of thesensors300,400 may also be provided in the form of a single use sensor which may be particularly desirable in the case where thesensors300,400 come in direct contact with bodily tissues or fluids, e.g. blood, cerebrospinal fluid, or fluid filled epidural space. For example, thesensor300 may include a separate bodyfluid pressure sensor305 and a microchip in the form of aprogrammable memory320,FIG. 3, where theprogrammable memory320 may be used to track usage of thesensor300 and thereby limit thesensor300 to a single use. Information communicated with thesensor300 andmemory320 may be encrypted and coded to ensure security of the use of thesensor300. Alternatively or additionally,sensor300 can have an internal on-chip timer that allows a specified amount of time for use of the sensor, after which thesensor300 expires. These features mitigate the potential for use on multiple patients and help to control against counterfeit products. Thesensor400 may be similarly configured for single use.
• The data collected from thesensors300,400 may be transmitted to thecontroller device500 for further processing, after which the processed data may be transmitted via acable4 or wirelessly to adisplay device600, such as a computer, smart phone, tablet, or other handheld device, for viewing by the clinician,FIG. 1. Thecontroller device500 may include a circuit board, central processor unit, rechargeable battery, connectors for wired communication, and/or antennas for wireless communication via Wi-Fi, Bluetooth® or other suitable communications standard. Thecontroller device500 may both process the received data and control and provide power to thesensors300,400. Thedisplay device600 may also further process the data prior to display and may include a variety of input elements such as buttons, a touchscreen, voice activated commands, scanning, etc. to transfer information into thecontroller device500. Alternatively, thedisplay device600 may receive the data directly from thesensors300,400 and control the operation of thesensors300,400 so that aseparate controller device500 is not required,FIG. 2. In this regard, thedisplay device600 may include a software application that can collect, process and display input data received from the two or moreseparate input sources300,400 with or without use of thecontroller device500. The data to be displayed by thedisplay device600 may include, but is not limited to, anobjective pressure value630, a graph of objective pressure overtime610, and apulsatile waveform620 representative of the contractive nature of the heart or cardiovascular system,FIG. 2. A prototype of thedevice controller500 was constructed for use in thesystem100 ofFIG. 1.
Prototype Controller Circuit
• FIG. 6 illustrates a schematic of thecircuit550 used in theprototype controller500 ofFIG. 1. (Thecircuit550 also represents at the component-level implementation of block diagram elements shown inFIG. 3. Reference to corresponding elements ofFIG. 3 are provided parenthetically.) As shown inFIG. 6, two different communication options were provided, and both were tested: wireless communications via Bluetooth® transceiver U2 (e.g.,transceivers532,534,FIG. 3), and direct wire communications via the USBserial data cables210,410,FIG. 1, connected to connector J1,FIG. 6. (Specifications for all components of thecircuit550 are provided in Table 1 below.) Theprototype100 collected data from the twosensors300,400 and provided the data to thecontroller500 where the data were formatted for presentation to a user.
• In theprototype100, a Nonin Medical, Inc Xpod® 3012LP External OEM Pulse Oximeter with 8000A Reusable Finger Clip pulse oximetry sensor was used for thefinger pulse sensor400. Thefinger pulse sensor400 produced a continuous stream of serial data which were input on connector J3. The data from thefinger pulse sensor400 were provided to the unit serialinput receiver channel1 at pin38 of a microprocessor U3 (e.g.,microprocessor520,FIG. 3). A standard baud rate transmission was used which was set by resistor R16. The data were collected and assembled into a format simplified for use by thedisplay device600.
• The in-line pressure sensor300 was a piezoresistive bridge design Model MER200 from Merit Medical, Inc and was attached to connector J4,FIG. 6. The reference voltage used to power the in-line pressure sensor300 was provided directly from the lithium-ion battery BT1 in thecircuit550. The in-line pressure sensor300 was connected through anadapter212,FIG. 1. Theadapter212 had several functions: to easily connect thesensor300 to thecontroller500 through an RJ12 quick connection connector J12; to provide power turn-on by interlock connection to the battery BT1; and, to permit identification and use management of the in-line pressure sensor300 by a one-wire memory device.
• Amemory device320 may be present in the in-line pressure sensor300,FIG. 3, to identify and serialize the in-line pressure sensor300 allowing traceable data to be collected and stored by thedisplay device600. In the prototype such a memory device was in theadapter212. Use of thememory device320 could also help mitigate the potential for use of thepressure sensor300 on multiple patients. Thesensor300 andadapter212,FIG. 1, may be disposable components intended for single use on one patient.
• Since thedevice100 had a user accessible connector J4, thecircuit550 included a protection against Electro-Static Discharge (ESD) events which could be caused by the accumulation of excessive static charge. Diodes D4-D9 were used to clamp the inputs of connector J4 to protect the internal circuitry,FIG. 6. Theadapter212 internally jumpered together pins4 to5 at connector J4,FIG. 6, which provided a connection path from the internal battery BT1 negative terminal to the remainder of the components ofcircuit550. Thus, thecircuit550 was powered on when theadapter212 was attached to the connector J4, which also helped mitigate exposure leakage current to users and patient when no adapter was present. Connector J4 was also used to charge the battery BT1 using anexternal charger10 attached to J4 viacable2,FIG. 1. Thecircuit550 was not powered when thecharger10 was attached; only the battery BT1 was charged. The charge current was limited and monitored to provide protection against battery fault/fire protection.
• As shown inFIG. 6, the signal from the in-line pressure sensor300 was presented to chip U4, a high resolution 24-Bit analog-to-digital converter, (e.g., A/D converter510,FIG. 3). The analog-to-digital converter U4 used, for its reference voltages, the same battery/ground voltage that powered the in-line pressure sensor300. Hence, the analog-to-digital converter U4 made a ratiometric measurement of the signal from the in-line pressure sensor300, and no correction was needed for gain and offset. The raw output of the analog-to-digital converter U4 was multiplied by a constant that was determined by the gain of the Merit MER200, which was pre-calibrated and adjusted during manufacturing. Resistors R14 and R15 of thecircuit550 provided mitigation for possible broken sensor leads for the in-line pressure sensor300. In the event of a breakage, the pressure reading from the analog-to-digital converter U4 was driven to an upper or lower extreme and thus became invalid.
• The data from the analog-to-digital converter U4 were sent to the microprocessor U3 over a serial peripheral interface (SPI) serial channel. The data from the analog-to-digital converter U4 were assembled in 3 bytes which were re-assembled in the microprocessor U3 as a 32-Bit word representing thecatheter310/needle pressure.
• The microprocessor U3 maintained some data in non-volatile memory which included a device serial number, catheter gain correction, and general hardware settings. This data could be transferred to and changed by commands sent from thedisplay device600. This information was stored in EEPROM memory internal to the microprocessor U3.
• While gathering the in-line pressure sensor data from the analog-to-digital converter U4, the microprocessor U3 also attempted to measure the cardio-induced pulse rate, if present, in the waveform signal from the in-line pressure sensor300. An average value was calculated for the waveform signal and subtracted from the raw data to provide a zero-centered waveform. The zero-centered waveform was processed to identify zero-crossings in the zero-centered waveform from which the period of the peaks and valleys was determined. A measurement of the period from the peaks/valleys was made and converted into a beats-per-minute numeric value. The numeric value and the positive zero-crossing information was passed via a communication channel to thedisplay device600. Additional details on the operation of microprocessor U3 are discussed below in connection withFIG. 8.
• As shown inFIG. 6, crystal Y1 was the clock source for microprocessor U3. The internal timing measurements and communication rate were established from this frequency choice. The frequency was chosen to provide sufficient computational speed while reducing radiated emission from thecircuit550. The 3.7 volt battery BT1 voltage also helped mitigate emissions. Voltage dividers consisting of R1/R2 and R9/R10 scaled the voltage from battery BT1 and radio transceiver U2 to a value in the range of the analog-to-digital converter internal to microprocessor U3 and allowed measurement of the supply voltages. This design was capable of operating with battery voltages below 3.0 volts. Over 12 hours of continuous operation was possible before battery recharging was required.
• The microprocessor U3 was programmed in-circuit by attaching a standard Microchip Technologies programmer to J2. The code could be changed in-the-field as the software design included a boot-loader section. After first programming, a production jumper JP2 may have a solder connection placed across it to protect thecircuit550 from future programming. The jumper JP2 also improves protection against ESD events.
• Thecircuit550 included two options for communication with thedisplay device600. When the USB cable option was used, a Future Technologies Digital International (FTDI) serial-to-USB cable4,FIG. 1, was connected to jumper J1 on the “b”-side, i.e., pins b2-b7. This provided direct attachment of thecable4 toserial channel2 of the microprocessor U3. The USB cable option was configured as a full implementation of RS-232 (TTL) using flow control CTS/RTS. TheSmart USB cable4 was powered by thedisplay device600 to which the USB connection was made. Power was not provided through thecircuit550. At thedisplay device600, the USB port was configured as a virtual communications serial port.
• For wireless Bluetooth® communication, theFTDI cable4 was removed and jumpers were placed across pins3-8, a-to-b of jumper J1. The choice of communication baud rate was selected based on the default configuration of Bluetooth® transceiver, U3. The same baud rate was used for the FTDI USB cable. This allowed the microprocessor U3 to operate without regard to whether the information and commands were transferred from thedisplay device600 via USB or Bluetooth® communications.
• The radio transceiver module U2 was a microchip design that simulated serial communication to thedisplay device600 and was pre-certified to meet the requirements of the FCC and EU standards for RF performance. The Green LED D2 indicated the radio transceiver module U2 was powered while the Red LED D3 flashed during data transmission,FIG. 6. The mode jumper JP1 was normally shorted and was used only for debugging purposes. Supervisory circuit U1 provided power-on and low-voltage shutdown of the radio transceiver module U2. Thedisplay device600 was responsible for pairing and bonding to the transceiver antenna AE1 of the radio transceiver module U2. Operation of the transceiver U2 occurred according to the frequencies and protocols defined for Bluetooth® BLE. The radio transceiver module U2 was defined as a server device providing data to a slave. The radio transceiver module U2 wirelessly communicated with thedisplay device600, in the case of the prototype a tablet (Dell® Latitude 7200, 2-in-1 tablet), which executed the software for analyzing and displaying the signals from the twosensors300,400.

• Parts list for components shown in FIG. 6.

  Reference(s)	Part Number	Value	Description	Manf.
  AE1	—	Antenna	PWB trace Antenna	—
  BT1	LP503562JB	Lithium Ion	Battery Lithium Polymer	Jauch Quartz
  		Battery	1S1P 1250 MAH 3.7 V BATT
  			LITH POLY 1S1P 1250 MAH
  			3.7 V
  C1, C4, C6, C9,	ECA-1EM100B	10 uf	Capacitor, Aluminum, 10 UF	Panasonic
  C11, C13, C17,			20% 25 V RADIAL	Electronic
  C18, C20				Components
  C2, C3, C5,	C320C104K5R5TA7303	0.1 uf	Capacitor, Ceramic, 0.1 uf,	Kemet
  C10, C12, C14,			50 v, X7R Radial
  C15, C16, C19,
  C21
  C7, C8	C315C220K2G5TA	22 pf	Capacitor Ceramic, 22PF	Kemet
  			10% 200 V COG RADIAL
  D1, D4, D5,	1N4148	1N4148	Diode, General Purpose,	ON
  D6, D7, D8, D9			100V 200 MA DO35	Semiconductor
  D2	HLMP-CM1G-350DD	Green	LED GREEN CLEAR T-1 ¾	Broadcom
  			T/H	Limited
  D3	HLMP-1700-B0002	Red	LED RED DIFFUSED T-1 T/H	Broadcom
  				Limited
  J1	67996-416HLF	Communications	Connector, Header, Vert,	Amphenol
  		Option	16P0S 2.54 MM	ICC (FCI)
  J2	68000-406HLF	Progrm. Conn.	Connector, Header, Vert,	Amphenol
  			6POS 2.54 MM	ICC (FCI)
  J3	LX60-12S	Xpod Connector	Connector Receptacle 12P	Hirose
  			0.02 GOLD SMD R/A	Electric Co
  				Ltd
  J4	0950097667	ID Adapter Conn.	Connector, CONN MOD	Molex
  			JACK 6P6C R/A UNSHLD
  JP1	—	Mode Jumper	Solder Jumper, PWB trace	—
  JP2	—	Production	Solder Jumper, PWB trace	—
  		Jumper
  R1, R2, R8, R9,	CFR-25JB-52-47K	47.0K	Resistor 47 KOhm ¼ W 5%	Yageo
  R10			Axial
  R3, R7	CFR-25JB-52-470R	470	Resistor 470 Ohm ¼ W 5%	Yageo
  			Axial
  R4, R6, R17	CFR-25JB-52-10K	10.0K	Resistor 10 KOhm ¼ W 5%	Yageo
  			Axial
  R5	CFR-25JB-52-100K	100K	Resistor 100 KOhm ¼ W	Yageo
  			5% Axial
  R11	CFR-25JB-52-68K	68K	Resistor 68 KOhm ¼ W 5%	Yageo
  			Axial
  R12, R13	CFR-25JB-52-1K	1.0K	Resistor 1.0 KOhm ¼ W	Yageo
  			5% Axial
  R14, R15	CFR-25JB-52-10M	10M	Resistor 10 MOhm ¼ W	Yageo
  			5% Axial
  R16	CFR-25JB-52-4K3	4.3K	Resistor 4.3 KOhm ¼ W	Yageo
  			5% Axial
  R18	CFR-25JB-52-2K2	2.2K	Resistor 2.2 KOhm ¼ W	Yageo
  			5% Axial
  R19	CFR-25JB-52-10R	10	Resistor 10 Ohm ¼ W 5%	Yageo
  			Axial
  U1	MCP112T-270E/MB	MCP112T	IC SUPERVISOR 1 CHANNEL	Microchip
  			SOT89-3	Technology
  U2	RN4871-I/RM130	RN4871	Bluetooth ® BLE Module,	Microchip
  			shielded	Technology
  U3	PIC18F87K22-I/PT	PIC18F87K22-xPT	IC MCU 8 BIT 128 KB FLASH	Microchip
  			80TQFP	Technology
  U4	ADS1232IPWR	ADS1232	IC ADC 24 BIT SIGMA-DELTA	Texas
  			24TSSOP	Instruments
  Y1	ECS-160-S-5PX-TR	16 MHz	Crystal Oscillator, 16.0 MHz,	ECS Inc.
  			series resonant

Display Device
• Turning to thedisplay device600 and signal analysis in more detail, thedisplay device600, working alone or in concert with thecontroller device500, may produce useful data and alerts to the clinician to aid in the placement of theneedle302 and/orcatheter310, including providing an indication of patency of thecatheter310,FIGS. 2, 4.FIG. 4 schematically illustrates an actual screenshot provided on thedisplay device600 as used with the workingprototype100 ofFIG. 1, which included thecontroller device500 withcontroller circuit550.FIG. 4 provides but one exemplary output configuration for data in accordance with the present invention.
• With reference toFIG. 4, adisplay450 on an LCD screen of thedisplay device600 included two graphs. The upper half of the screen displayed an “Objective Pressure Graph”451 and in the lower half displayed a “Pressure Waveform Graph,”455 showingwaveforms452,453 corresponding to data collected from thesensors300,400, respectively. In addition, a Dialogue Bar was provided below the Pressure Waveform Graph. These two graphs can be shown simultaneously or can be displayed individually at different times.
• The objective pressure was displayed in both the Objective Pressure Graph showing a scrolling graph of objective pressure vs.time451 and as a real-timenumeric value401,FIG. 4. A Maximum Pressure Line was also displayed, which could be changed by the clinician. When the objective pressure exceeded this line, an audible alert was sounded, though it is understood that the audible alert could have been a visual or some other type of alert. Theobjective pressure401 corresponded to pressure generated by thehandheld syringe200 as the clinician applied a force to the plunger of thesyringe200. The graphing of the objective pressure data was performed on a continuous basis and in real-time, and the scaling could be changed by pressing the Up and Down arrows (↑, ↓) on the left-hand side bar of theObjective Pressure Graph451, which allowed scaling to be changed in real-time. If the pressure detected reached the Maximum Pressure Line without the expression of fluid, the clinician could conclude that theneedle302 and/orcatheter310 is occluded. A negative slope in the Objective Pressure Graph could indicate a dissipation of the pressure in theneedle302 and/orcatheter310, further indicating that theneedle302 and/orcatheter310 was not occluded. Thus, the real-time changes in the Objective Pressure Graph provide vital information to confirm or rule out anoccluded needle302 orcatheter310 even when the data from thewaveforms452,453 are ambiguous. Therefore, the Objective Pressure Graph provides needle or catheter patency information in addition to the information displayed inwaveforms452,453.
• As to thePressure Waveform Graph455, thewaveforms452,453 were constructed using a high resolution, high-speed sampling algorithm in which between 30 to 90 samplings per second were taken. In the prototype, average values of thewaveforms452,453 were calculated and drawn to thedisplay device600 to maintain thewaveforms452,453 centered on the Pressure Waveform Graph. Within 4 seconds (or some other programmed period of time in the software), the displayedwaveform452,453 was calculated to a mean pressure value and positioned to be centered within thegraph455 relative to the meanhorizontal line454 displayed inFIG. 4.
• Thewaveforms452,453 from the first andsecond sensors300,400 had peak-to-peak crests (and zero crossings) that were reflective of the pulsatile nature of the heart contracting and were consistent with the value of the number of heart beats-per-minute (bpm). The heart rate in beats-per-minute could also be calculated from the zero crossings. However, two zero-crossings are present per beat, so either time between successive positive-slope zero crossings or time between successive negative-slope zero crossings were indicative of heart rate. The twowaveforms452,453 could be visually compared on thedisplay450 by the clinician. In addition, a real-timenumerical value402 for the heart rate detected by thefirst sensor300 was displayed, as well as the real-timenumerical value404 for the heart rate detected by thesecond sensor400,FIG. 4. The detection of a bothwaveforms452,453 from the twoinput sources300,400 provides the clinician with an understanding as to the position of theneedle302 and/orcatheter310 within an anatomic structure that transmits a pulse wave from the cardiovascular system. Two sets of up and down arrows (↑, ↓) on the left-hand side bar of the Pressure Waveform Graph were usable to scale the heights of each of thewaveforms452,453 individually. In addition, an audible bpm beep could be provided which sounds with the same frequency as the pulse rate shown in eitherwaveform452 orwaveform453. In such a case display of thewaveforms452,453 associated with the audible bpm beep could be omitted, with the audible bpm beep filling the role of providing such information to the clinician.
• Alternatively, thewaveforms452,453 could be displayed in a variety of different formats. Exemplary formats may include,(and are not limited to): a continuous waveform which may be represented as a pressure waveform with peak-to-trough continuous line; a non-continuous line in which the peak-to-peak is displayed; or, a blinking light that is representative of the peak-to-peak pressure values that are detected by the input sources. In addition, it may be that thewaveforms452,453 are not both displayed but only a visual alert is provided confirming that the signals are coordinated with the peak-to-peak signal representative of heart beats-per-minutes from the twoindependent sources300,400. For instance it is possible that neither of thewaveforms452,453 are displayed, and that the peak-to-peak signals are represented as an audible or haptic signal. Or it is possible to rely solely upon the numeric values displayed as beats-per-minute. Further, any combination of these display techniques may be used.
• As shown inFIG. 4 the Dialogue Bar included (from left to right): 1) a “Zero” button to calibrate the in-line pressure sensor300; 2) anobjective pressure value401 for the in-line pressure sensor300; 3) heart rate beats-per-minute (bpm),402 from the in-line pressure sensor300; 4) a “Sync alert”403 indicating that the heart rate values402,404 were correlated to confirm that a single source (the heart) has produced both of these signals; 5) a heart rate beats-per-minute (bpm)404 from thefinger pulse sensor400; 6) anoxygen saturation value405 in percent; and 7) an “{circumflex over ( )}image{circumflex over ( )}” button to capture the image on the screen.
• Thedisplay device600 in the prototype performed an analysis to determine whether the twowaveforms452,453 were correlated at their fundamental frequency, which frequency corresponded to the cardiac bpm (beats-per-minute) if thewaveform452,453 represented the cardiac pulsewave. If not, the fundamental frequency would correspond to some other spurious signal not related to the cardiovascular system. Two signals were considered correlated in frequency even if a phase offset between the two signals were present, such as illustrated in thewaveforms452,453,FIG. 4. A phase offset between the signals may be present due to the fact that the cardiac pulse may travel through different tissue types and different distances to arrive at each of thesensors300,400.
• If thewaveforms452,453 were frequency-correlated, the “Sync alert”403 would flash on/off to alert the clinician that the bpm rates from each of thesensors300,400 were found to be correlated, i.e., that the frequency of signals from thesensors300,400 were sufficiently matched within a selected deviation, with an acceptable range of deviation of 2 bpm to 15 bpm. Thus, the clinician was provided with a confirmation of location of theneedle302/catheter310 at the desired location when the “Sync alert”403 was activated. In addition, an alert may optionally be sounded if the twowaveforms452,453 were not correlated, indicating that theneedle302 and/or thecatheter310 was not positioned properly. Any of these alerts may be visual, audible, haptic, or any combination thereof.
• The signals detected by thesensors300,400 may also be analyzed by a variety of correlation techniques to determine the cardiac pulse rate, including but not limited to, waveform analysis, pulse-rate comparison (heart-rate, beats-per-minute), cross-correlation, and combinations thereof. In yet another embodiment a cross-correlation analysis may be performed on the data from thesensors300,400 producing a matched frequency of the two signals with time-shift producing definitive positive correlation based on set a criteria. In this case, the cross-correlation may be the sum of the product of the two signals shifted relative to each other over a period of not less than one complete cycle of the longer period waveform. In yet another embodiment auto-correlation may be used to normalize the values for better threshold detection comparison of the cross-correlation peak value. In yet another embodiment the auto-correlation peak spacing can be used to verify the validity of the BPM measurements made of each sensor data.
• In yet another embodiment a cross-correlation analysis may be performed on the data from the twoinput sources300,400 producing a definitive positive correlation based on set criteria. Illustrated inFIG. 9 is an example of a cross-correlation technique in accordance with the present invention that may be used to objectively determine the degree of correlation of the twosignals452,453 fromsensors300,400. Exemplary details are specific to an implementation for thecontrollers500 and600. For discrete data samples as collected byexemplary devices100,150 of the present invention, the cross-correlation function may be defined as
• $\left(f*g\right)\left(\tau \right)\stackrel{\Delta }{=}\sum _{\mathrm{t0}}^{\mathrm{t0}+T}\stackrel{\_}{f\left(t-\tau \right)}g\left(t\right)\mathrm{dt},$
• where T is the period (number of samples) of the waveform being analyzed, and τ is the sliding offset between the two waveforms.
• Basically, the correlation function generates a series of sum-of-products over the entire sampled data set to come up with values of the correlation coefficient for each τ value. The correlation coefficients calculated have a maximum value at shift τ_max. Due to possible velocity propagation delays through the patient tissue, the twowaveforms452,453 may have an offset in the peak correlation coefficient position, in which is τ_max≠0. Themethod900 shown inFIG. 9 presents a representation of an exemplary method which may be used for correlation detection in accordance with the present invention. The collected data from the in-line pressure sensor300 is input atstep902. The pressure reading from the finger-sensor400 is input atstep904. The data are collected synchronously bydisplay device600, and hence the pair of data (902,904) represents a single instance in time. The sampled data are placed in circular FIFO buffers906,908. The size of thebuffers906,908 is determined by the period of thepulsewaves452,453. The longest period occurs at the lowest pulse rate which is defined to be 40 BPM. With a data sampling frequency of 75 samples/second, a minimum of 112 samples represent one complete wave form in eachbuffer906,908. In addition, the τ shift could be up to 112 samples as well. Hence, the minimum buffer size to perform a complete cross-correlation function is 224 for the combinedbuffers906,908. In this exemplary case, the buffer length may be chosen as 256, which makes circular FIFO buffer management easier and also provides some addition space in thebuffers906,908. An extra 32 buffer positions of padding (256−224=32) may be provided that allow new data to be inserted into thecircular buffers906,908 without corrupting the 224 values being processed to determine the correlation coefficients. Thebuffers906,908 may be simultaneously written and read which eases the computational burden on the microprocessor in thedisplay device600. The computation need not be completed in a single data sample time. Real word correlation is generally a serial process of mathematical operations. Each new correlation check is begun at the position of the last data written to thecircular buffers906,908 and works backwards.
• Thecorrelation algorithm902 may begin at the last data position written and work backwards through the data from this point. Based on the values of buffer size and assumed pulse rates, the complete computation must finish before 32 additional data samples are taken, that is: 32 samples/75 samples/second, or 0.43 seconds. In thistime 112 sum-of-products are calculated. The sum-of-product,step914, is the accumulation of 112 multiplications910a-910dof data in eachbuffer906,908. Each correlation coefficient calculated atsummation point914 may be temporarily stored in anarray buffer918. Each value saved is the sum-of-product for 112 offsets of the τ parameter. The τ offset is the starting from which data is read from thebuffers906,908 for each sum-of-product calculation. Thearray buffer918 results may be analyzed to determine the degree of correlation between the pulsewaves. To normalize the cross-correlation results, auto-correlation may also be performed. Numerically, the cross-correlation results inbuffer918 should be values between +1.0 and −1.0. Values near 0.0 are considered to be non-correlated and indicated as not “In-Sync” on thedisplay device600. Values greater than a determined threshold are considered significantly correlated and provide an indication to the clinician of correct placement of theneedle302 and/orcatheter310. Should the pulse rate be greater than the minimum design value, multiple correlation coefficients will be produced. For example, at 80 BPM pulse rate, there will be 2 correlation maximums. Thecorrelation algorithm920 may analyze the data for maximum peak and generally select the τ offset value closer to zero. All of the selected correlation coefficients may be output to thedisplay device600. The analysis may include consideration of the measured BPM from eachsensor300,400. BPM may also be obtained by analysis of the auto-correlation measurements made on eachwaveform452,453. Though possibly lacking in resolution detail, the separation measurement of multiple peaks in auto-correlation may be another measurement of pulse rates from eachsensor300,400 and maybe useful information for making the correlation detection indication.
Controller Device Algorithm
• In another of its aspects, devices of the present invention may use themethod850 in confirming catheter or needle placement and patency,FIG. 8. The flowchart ofFIG. 8 represents the software logic that was used in the prototype to calculate the beats-per-minute pulse rate as measured by the in-line pressure sensor300. The software executed in the microprocessor U3,FIG. 6, ofcircuit550 of thecontroller device500. The software identified the zero-crossings of thecardiac pulsewave signal452 in theneedle302 and/orcatheter310,FIG. 4. The beats-per-minute rate was determined by measuring the period of time between successive positive zero-crossings of thepulsewave signal452. The positive zero-crossings were selected, because the ascending aortic systolic pressure wave has a faster rate of change and hence provides a more accurate point of measurement than the descending slope of the negative zero-crossings. The software operated in aloop867 using a state machine to analyze thepulsewave452.
• The state machine was initialized atstep851 when software began executing,FIG. 8. The STATE variable determined which side of the mean average theloop867 was last processing. A Filter Counter variable was provided which was incremented and decremented based on whether the difference between measured value and the mean average was above or below zero. The Running Average Filter was also initialized atstep851. Atstep852, the pressure reading was obtained from the analog-to-digital converter U4 ofFIG. 6. Analog-to-digital conversions were produced by hardware events and occurred at approximately 80 samples per second. A new value of the pressure sample was obtained atstep852 and was sent to thedisplay device600. The new pressure sample was also used inmethod850. Specifically, the new pressure sample was added into the Running Average Filter by computing the running average atstep853. The Running Average Filter output a value which was the average of the last 128 pressure samples. Atstep854 the pressure sample had the average value subtracted to generate the Difference value which was stored atstep855. Next, a decision was made atstep856 to determine if last previous operation was looking for a positive (POS) or negative (NEG) zero-crossing. If the STATE atstep856 was POS, then the software branched to step862 looking for a negative crossing. The criterion for a negative crossing was that the Difference was less (more negative) than a negative threshold of −0.1 mmHg. If the Difference did not meet this criterion, then the loop passed to step866 where it waited for the next pressure sample to repeat, viastep860, the processing ofmethod850. Returning to step862, should the Difference meet the criterion, then the Filter Counter was decremented,step863. Atstep864 the count value was tested to determine if the count was less than −3. If not, control passed to step866 andmethod850 repeated by passing to step866 and waiting for the next sample. Normally the last value of the Filter Counter would be +4 following the last positive zero-crossing. Hence the Filter Counter must be decremented 8 times to reach the value −4 tested, and the STATE variable was then set to NEG indicating that a descending zero-crossing was found,step865. The Filter Counter value was forced such that it does not exceed −4. Theloop867 then returned to wait for the next pressure sample atstep866.
• Returning to step856, if the STATE atstep856 was NEG (i.e., not POS), that is looking for an ascending zero-crossing, the branch would continue to step857. At step857 a test was made to determine if the criterion for a positive zero-crossing was met. The Difference pressure must exceed +0.1 mmHg. If not, themethod850 repeated jumping to step866 and waited for another pressure sample. Should the criterion be met, control passed to step857. The Filter Counter value was incremented atstep858. Typically the counter would begin incrementing from −4 after the last descending zero-crossing. Atstep859 the count value was tested to determine if sufficient positive differences had been found to justify indication of an ascending zero-crossing of pressure, that is that the count exceeded +3. If not, control passed to step866 andmethod850 repeated by passing to step866 and waiting for the next sample. Should the Filter Counter exceed +3 atstep859, then control passed to step860. Atstep860 the STATE variable was set to POS and the Filter counter was limited to +4. At this point a valid positive zero-crossing had been determined. An algorithm measured the period of time since the last positive zero-crossing occurred. The period was measured in milliseconds by a time base maintained in microprocessor U3 using interrupts. The period measurement was dynamically adjusted to provide good BPM measurements. At fast heart rates greater than 200 BPM, up to 4 zero-crossings are counted to give a resolution better than 1.0 BPM. At low pulse rates, below 60 BPM, a single zero-crossing period measurement was performed to allow quicker updates of the measured heart rhythm. The final calculation of period was performed atstep861 and the calculated BPM value,402 inFIG. 4, was sent to theprocess controller600 for display to the user and for pulse correlation matching with theheart rate404.
• A further understanding of how thedevices100,150 of the present invention may operate with regard to generating the data for display on thedisplay device600 is seen in the block diagram800 ofFIG. 5. In this diagram, the “cardiovascular pulse sensor device” block corresponds to thesensor400 and the “pressure sensor device” block corresponds to thesensor300. Communication among the components and processes is illustrated as wireless using the conventional symbol for Bluetooth® communication, though the components and processes could communicate via other methods such as Wi-Fi or hard wired.
• Theapplication software803, which can run on thedisplay device600, can include thestep804 for writing a time/date stamp to thesensor300 to assist in ensuring that thesensor300 is used for only a single use. As part of the operation, the software also obtains the data from thesensors300,400 atstep805. Collection of data continues until complete,step806, and the Bluetooth® radio is disabled,step807. During the data collection step805 asub process808 can run which includes functions such as creating the graphical display of thepressure810; calculating theexcessive pressure alert811; displaying thenumerical pressure812; performing the correlation detection of the data received from thesensors300,400,step813; and, issuing thevarious alerts814.
• In addition, an authorization scheme of the present invention may include a computer chip, SIM, or other uniquely coded circuit in theadapter212 orsensor300, forexample chip320. The chip, SIM, or other uniquely coded circuit may be disposed in communication with thecontroller device500 and/ordisplay device600, and may be read by an authorization program or circuit in the controller and/ordisplay device500,600. If the chip, SIM, or other uniquely coded circuit is genuine, the controller and/ordisplay device500,600 will operate properly, if not, thesensor300 may be disabled and a warning such as “unauthorized adaptor detected” can be posted on thedisplay device600 and optionally a warning sound may be made, including but not limited to a vocalization of words, an alarm, or other warning signal or any combination thereof. The coded circuit may also be coded for a one-use function whereby the authorization program or circuit in controller and/ordisplay device500,600 will detect if aspecific sensor300 was previously used and, if so, again disable the controller and/ordisplay device500,600 and post a warning.
Description of an Exemplary Method
• In another of its aspects, devices of the present invention may provide the clinician with a particularly useful method of confirming catheter or needle placement and patency, such as themethod700 illustrated inFIG. 7. For example, the clinician often needs to determine if a catheter is: i) clogged or functioning and/or ii) if the catheter has moved from the target position, collectively beginning atstep702. Making such a determination may necessitate the following actions: 1) flush the catheter to determine if it is clogged or clear and then 2) infuse a bolus of drug. In making such a determination, the clinician may connect an in-line pressure sensor between the catheter and a syringe used to flush the catheter,step704, and may attach a secondary input source to detect a heartbeat, such as a photophelthysmography fingertip clamshell to detect the heartbeat. The syringe and in-line pressure sensor, and any other disposables such as a catheter, may be primed with fluid,step706. The in-line pressure sensor and secondary source may be operably connected, wired or wirelessly, to a display device for viewing by the clinician,step708. A maximum objective pressure value may also be set on the handheld device and remain stored in the handheld device for future use. The maximum pressure value may be set anywhere between 75 mm/Hg to 500 mm/Hg, for example. When the maximum pressure value is reached an alert may be sounded as an audible sound or tone. A spoken word may also be used to alert the clinician that the maximum pressure has been exceeded.
• Signals from the in-line pressure sensor and secondary source (e.g., a finger pulse sensor) may be compared and analyzed by a controller and/or display device, such as one or more of thecontroller500 anddisplay device600. If the two signals are found to be correlated in frequency (that is beats-per-minute of a heartbeat), an alert may be displayed on the display device as a flashing box and/or an audible alert sounded, indicating that the catheter is properly positioned.
• If a pulsewave is detected,step710, the clinician may proceed with flushing the catheter,step712. The clinician may again observe the response on the display device,step714. If no response is observed and no pulsewave correlation is found between the signal from the in-line pressure sensor and the secondary input source,step722, the pulsewave detected at step710 (or step732 as described below) is a false-positive finding. The clinician then concludes that the catheter is not properly positioned, and the catheter is removed,step724. Alternatively, if a response is observed atstep714, and the clinician observes that pulsewave correlation is found between the signal from the in-line pressure sensor and the secondary input source,step716, the clinician can bolus the patient with the drug,step718, and observe the therapeutic output,step720.
• Returning to the situation where no initial response is observed atstep708, the clinician may observe the objective pressure graph to determine patency of the catheter. In such a case the clinician will likely see that no pulsewave is detected at all,step726, but will still proceed with flushing the catheter,step728. Again, the clinician may observe the response on the display device,step729. The clinician may then determine if the catheter is clogged by observing an absence of a gradual reduction in the pressure;
• this may be observed by viewing an objective pressure vs. time graph in which the slope of the curve demonstrates whether fluid is flowing out of the catheter and into the tissues. If the pressure does not dissipate over time,step736, and no pulsewave correlation is found between the signal from the in-line pressure sensor and the secondary input source,step738, the clinician can conclude that the catheter is clogged and the catheter may be removed,step740. Alternatively, if a response is observed atstep729 and the response is a reduction of pressure,step730, the clinician may observe that pulsewave correlation is found between the signal from the in-line pressure sensor and the secondary input source,step732. In such a case, the clinician may proceed with flushing the catheter,step734, and may proceed withsteps714 through724 as described above. The example in the proceeding sections describe the method for use with a catheter, it is understood that a similar method could be used for placement of a needle within a patient performed with the same steps described.
• It is anticipated that themethod700 could be used for confirmation of the position of a catheter in the epidural space or the intrathecal space, for example. In addition, themethod700 could be used to determine when a needle or catheter is positioned properly in a vessel such as a vein or artery for an infusion. It is also conceivable that such a system could be used for aspiration of bodily fluids in which the needle position within a target confirmed by a pulsatile waveform is necessary prior to the removal of said fluid such as cerebral spinal fluid from the central nervous system. Themethod700 may also be used in situations where assessing the pulsatile nature of a tissue is vital. Devices and methods of the present invention may also be used to assess the perfusion status of vessels to a tissue or organ based on the quality (amplitude and cadence) of the pulsatile pressure waveform as seen in the pulse interval and amplitude of the waveform curve; for example, the perfusion status may be assessed in the extremities as it relates to diabetes, frost-bite, trauma, tissue grafting, etc.
• Thus, the above disclosure describes devices and methods that can confirm the location of a needle and/or catheter as well as the patency of properly located indwelling catheter. The devices and methods may provide essential confirmation through physiologic feedback that a needle or catheter has been positioned within an anatomic site. Devices in accordance with the present invention may detect the presence of cardiovascular signals from two separate input sources and determine if the signals are coordinated or not by analysis of the signals. A positive-correlation may be confirmed, verifying the position of a needle or catheter within the body and an alert may be provided in response. If a correlation cannot be established between the two cardiovascular signals, no alert is provided, which indicates that a needle and/or catheter is improperly positioned.
• These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. Accordingly, it will be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. For example, the apparatuses disclosed herein could incorporate a device to remotely monitor a patient, such as by Bluetooth, Wi-Fi or other device of transmitting the collected pressure data to the software loaded on a smartphone or computer workstation. The clinician would be able to assess the patient's condition related to the presence or absence of a pulsatile waveform. A communication module, optionally present in thecontroller device500 and/ordisplay device600, may relay data collected to either an on-line external communication system or directly to a specific communication target to relay this information for either real-time or retrospective review. It should therefore be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention as set forth in the claims.

Claims (32)

1. An apparatus for confirming placement of a hollow-bore structure at a desired treatment location in a mammalian subject, comprising:

a needle, a catheter or combination thereof to provide the hollow-bore structure, the hollow-bore structure having distal and proximal ends with respective openings thereat;

a first sensor disposed in fluid communication with the hollow-bore structure;

a syringe disposed in fluid communication with the first sensor, where each of the hollow-bore structure, first sensor, and syringe have a respective fluid passageway extending therethrough with all of the fluid passageways disposed in fluid communication to provide a continuous closed fluid pathway extending from the syringe through the first sensor to the opening at the distal end of the hollow-bore structure; and

a controller configured to receive a first signal in response to detection of a first property from the first sensor, the first signal indicative of a cardiac pulse in the fluid passageway of the hollow-bore structure, the first signal also indicative of an objective pressure in the fluid passageway of the hollow-bore structure, and the controller configured to receive a second signal in response to detection of a second property indicative of the cardiac pulse from a second sensor placed at a second location, the controller programmed to determine if the first and second signals are correlated to provide a comparison result, wherein controller is programmed to determine that the first and second signals are correlated at a fundamental frequency in the presence of a phase offset between the first and second signals whereby the comparison result provides an indication of placement of the hollow-bore structure relative to the desired treatment location.

2. The apparatus ofclaim 1, wherein the controller is programmed to provide an alert when the objective pressure exceeds a selected value indicative of an excess pressure in the fluid passageway of the hollow-bore structure .

3. (canceled)

4. The apparatus ofclaim 1, wherein the first sensor comprises an in-line pressure sensor disposed in fluid communication with the fluid passageway of the hollow-bore structure.

5. (canceled)

6. The apparatus ofclaim 1, wherein the second sensor comprises a finger pulse sensor.

7. The apparatus ofclaim 1, wherein the first property is one or more of a pressure, change in fluid volume, an electrical signal, and an optical signal.

8. The apparatus ofclaim 1, wherein the second property is one or more of a pressure, change in fluid volume, an electrical signal, and an optical signal.

9. The apparatus ofclaim 1, wherein the first and second properties relate to the same property.

10. The apparatus ofclaim 1, wherein the first and second properties relate to different physical properties.

11. The apparatus ofclaim 1, wherein the controller is disposed in wireless communication with one or more of the first and second sensors.

12. The apparatus ofclaim 1, wherein one or more of the first and second sensors includes a memory configured to store an indication that the first or second sensor, respectively, has been used.

13. The apparatus ofclaim 1, comprising an identification circuit embedded within or connected to one or more of the first and second sensors, wherein the identification circuit is configured to provide a signal to the controller, the signal including one or more of: a configuration signal indicative of physical characteristics of the first or second sensor; a verification signal indicative of the first or second sensor; and a use signal so that the controller can detect the number of times or length of time the first or second sensor was previously used.

14. The apparatus ofclaim 1, wherein the first signal represents one or more of a pressure, change in fluid volume, an electrical signal, and an optical signal.

15. The apparatus ofclaim 1, wherein the second signal represents one or more of a pressure, change in fluid volume, an electrical signal, and an optical signal.

16. The apparatus ofclaim 1, wherein the first signal has a first period and the second signal has a second period, and wherein the controller is configured to compare the first and second periods to provide the comparison result.

17. The apparatus ofclaim 1, wherein the first signal comprises a waveform having a first period and the second signal comprises a waveform having a second period, and wherein the controller is configured to compare the first and second periods to provide the comparison result.

18. The apparatus ofclaim 1, wherein the first signal comprises a first numeric value indicative of a frequency of the first signal, and the second signal comprises a second numeric value indicative of a frequency of the second signal, and wherein the controller is configured to compare the first and second numeric values.

19. The apparatus according toclaim 18, wherein one or more of the first and second numeric values is a cardiac pulse in beats per minute.

20. (canceled)

21. The apparatus ofclaim 1, wherein one or more of the first and second signals each comprise a respective waveform having a respective period and having a respective mean value, and wherein the controller is configured to detect zero-crossings of each of the respective waveforms through the respective mean value.

22. The apparatus ofclaim 1, wherein the controller is configured to create an alert signal when the comparison result is within a selected range.

23. The apparatus ofclaim 1, comprising a display operably connected to the controller for receiving one or more of the first and second signals and the comparison result from the controller.

24. The apparatus ofclaim 23, wherein the controller includes the display.

25. The apparatus ofclaim 23, wherein the display includes a first data section for displaying a pressure versus time in the lumen of the hollow-bore structure.

26. The apparatus ofclaim 23, wherein the display includes a second data section for displaying the first and second signals.

27. The apparatus ofclaim 26, wherein the first and second signals each include a respective waveform, and wherein the second data section includes a graph displaying as a function of time the respective waveforms of the first and second signals.

28. The apparatus ofclaim 23, wherein the display includes a section for displaying an alert indication when the comparison result is within a selected range.

29. The apparatus ofclaim 28, wherein the alert is one or more of an auditory, visual, and haptic signal.

30. The apparatus ofclaim 1, wherein the controller is programmed to perform a cross-correlation analysis of the first and second signals.

31. The apparatus ofclaim 1, wherein the comparison result does not include comparing different respective portions of the first signal.

32. The apparatus ofclaim 31, wherein controller is programmed to determine that the first and second signals are correlated by using a cross-correlation of the sum of the product of the first and second signals.

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