Injection needle / catheter positioning device using correlation analysis

Abstract

The present invention relates to an apparatus and method that allows a clinician to confirm the position of an injection needle or catheter within an anatomical site by relying on the combined sensing of two signals, such as a pressure signal and a cardiac pulse signal, and by identifying the correlation between the two signals to confirm the position of the injection needle or catheter.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for determining the position of a needle or catheter in a patient using correlation analysis. More specifically, it relates to correlation analysis such as comparison per beat or cross-correlation of waveforms between the objective pressure within the needle or catheter and the patient's heartbeat, but is not limited thereto.

Background Art

[0002] Currently, when measuring the pressure within an injection needle or catheter, there is no function to distinguish between the heartbeat wave detected within the injection needle or catheter and the pressure change that truly represents the heartbeat wave. The heartbeat wave is a pressure waveform that includes signals derived from the contraction of the heart and blood vessels and is defined as including information representing the heartbeat. It is conceivable that an injection needle or indwelling catheter may detect various non-cardiac pulsation sources within the body, such as respiratory changes and muscle movements of the diaphragm, and erroneously report the detected pulsation as a heartbeat wave. Also, patient body movements such as changes in the patient's body position may cause the measured pressure change and be misrecognized as being derived from the cardiovascular system. In particular, existing devices do not have an independent means to confirm that a specific pressure waveform is from the heart, so false detections where the detected waveform is from outside the cardiovascular system cannot be eliminated. On the other hand, determining the position and patency of an injection needle or catheter is a major concern for clinicians, such as when administering drugs to a patient. Therefore, when using this information as an indicator for the placement of an injection needle or catheter, it is very important to prevent the perceived pressure from being confused with other pressure change waves generated within the body, which will ultimately affect the patient's outcome.

[0003] For example, in clinical practice, it is common to administer medication after inserting a needle or catheter. However, blockage of the needle or catheter, or displacement from its original position, can make subsequent administration via the needle or catheter difficult. Therefore, it may be necessary to evaluate the catheter, determining whether it is blocked, functioning properly, or has moved from its initial location. Because it is difficult to accurately distinguish catheter function, clinicians face serious and sometimes dangerous problems, including the effectiveness of medications, catheter movement, catheter blockage due to deposits, and malfunctions caused by blood clots.

[0004] Furthermore, data shows that 10–25% of all catheters require replacement due to migration after placement. Clinicians have difficulty determining the cause of these catheter malfunctions. Typically, evaluating catheter function and placement takes 20–30 minutes, and since this is currently the only way to assess catheter function, clinicians wait while observing the patient's response to medication. Consequently, if a catheter malfunctions, evaluation can take a life-threatening amount of time, creating further risks and additional costs for the healthcare system. Thus, the difficulties and potential risks of catheter placement and monitoring are serious challenges, and therefore, predictable methods for distinguishing these conditions are of great value to both patients and clinicians.

[0005] Nevertheless, existing devices developed to detect pulsating waveforms are expensive, complex to use, and sometimes require the use of an electromechanical motor to deliver fluids to the patient. With such devices, clinicians cannot observe the objective pressure generated while manually injecting medication using a handheld syringe, as is commonly or preferred. Furthermore, existing systems do not provide two different physiological sources of heartbeat for determining and confirming the position of the injection needle or catheter, as they are not designed with input from multiple sources to separately compare and analyze heartbeat and pulsating pressure waveforms during use. Thus, in arriving at the present invention, the inventors recognized the shortcomings of prior art devices and methods for needle or catheter placement, such as: 1) detecting a cardiovascular input source used to directly compare heart rate with the location of the needle or catheter; 2) detecting a cardiovascular response directly via a fluid pathway and generating a pulse / min analysis for comparison with a secondary source known to detect heart rate by analyzing the information from the fluid pathway; 3) correlating and analyzing multiple signals to determine whether the needle or catheter is properly positioned in an anatomical location; and 4) providing a positive alert when these two signals are correlated to a degree that can be verified as true or false.

[0006] Therefore, there is a need in the art for inexpensive and simple devices and methods that can eliminate false detections when locating injection needles or catheters within the body, and such devices and methods would be of great value to clinicians and patients. The following are prior art documents related to the invention of this application (including documents cited in the international phase after the international filing date and documents cited when the application entered the national phase in other countries): (Prior art document) (Patent Document) (Patent Document 1) U.S. Patent Application Publication No. 2018 / 0116551 (Patent Document 2) International Publication No. 1996 / 005768 (Patent Document 3) U.S. Patent Application Publication No. 2018 / 0064870 (Patent Document 4) U.S. Patent Application Publication No. 2016 / 0135712 (Patent Document 5) U.S. Patent No. 5,727,553 [Overview of the Initiative]

[0007] In view of the above-mentioned and other needs, the present invention can, in one embodiment, provide an apparatus and method for using two or more different physiological sources indicating heart rate to determine the position of an injection needle or catheter before drug delivery or fluid aspiration. One of the sources may be a heart wave detected as a pressure waveform within the injection needle or catheter, such as an in-line pressure sensor, and the second source may be heart rate detection from a location known to emit heart waves or heart sounds, such as a fingertip pulse sensor. The two physiological sources can then be compared to confirm that the pressure waveform detected at the injection needle or catheter is indeed a heart wave, thereby eliminating false detections of heart waves at the injection needle or catheter. The comparison can be performed as a correlation analysis of signals from the two different physiological sources to determine whether the frequencies of the signals from the two different physiological sources are clinically equivalent. The correlation analysis can be performed, for example, as a comparison of the numerical values ​​of beats / minute of heart rate detected at each of the two or more different physiological sources, and / or by the cross-correlation of the waveforms detected at each of the two or more different physiological sources. Therefore, the present invention can perform a "needle / catheter position correlation analysis" as a comparison of two or more cardiovascular signals, which may include pulse rate / min, cross-correlation of pressure waveforms, and / or measurement of target pressure, for example, to determine the position of a needle or catheter in the body of a mammal.

[0008] Positive verification of the heart rate in a needle or catheter can establish both the correct position and patency of the needle or catheter. As a result, the apparatus and method of the present invention, through verified detection of the heart rate, can enable clinicians to more easily and confidently assess the proper placement of the needle or catheter in real time. These may be presented to the clinician as signals or warnings confirming proper placement of the needle or catheter. Consequently, verified real-time detection of the heart rate in a needle or catheter allows clinicians to use a manual syringe rather than an automated mechanical pump, enabling them to position the needle themselves and control the physical forces applied to the syringe for drug delivery or fluid aspiration. By more precisely controlling the physical forces, clinicians can also prevent catheter displacement due to excessive pressure. Excessive pressure during drug delivery can cause the needle or catheter to dislodge from the site because uncontrollable fluid pressure generates a "jet stream" at the tip of the catheter or needle.

[0009] In another embodiment, the apparatus of the present invention can provide the clinician with a target (i.e., measured) pressure value in the injection needle or catheter during the flushing phase. Knowing the objective pressure when the drug is injected can also help the clinician avoid excessive force and prevent excessive pressure. For example, the present invention can issue a warning to the clinician if the pressure value is exceeded. The warning can be audible, visual, tactile, etc.

[0010] Exemplary applications of the apparatus and methods of the present invention may include positioning an intracellular needle to a specific target site in the body, such as in epidural procedures or peripheral nerve blocks. In particular, the identification of the epidural space, the determination of the proximity of the needle to a neurovascular bundle in a local peripheral nerve block, and other medical procedures that require the placement of a needle or catheter tip to a specific location where a heartbeat is present (e.g., intrathecal cavity, intravenous, intraarterial, or organ of the body) can all benefit from the apparatus and methods of the present invention. Thus, the use of the apparatus and methods of the present invention at such exemplary target sites can replace current loss-of-resistance (LOR-TECHNIQUE) methods with greater reliability. Further advantages of the present invention, the apparatus and methods can be used with all types of needles and catheters placed in a patient at anatomical sites where rhythmic pulsations of the arterial system originate, and can be provided as an inexpensive and portable system.

[0011] In further embodiments, the present invention can achieve a number of objectives. For example, an objective of the present invention may be to detect a catheter pulsation waveform that confirms the presence of a cardiovascular pulse by comparing a first input with a second input from the cardiovascular system, such as a heartbeat detected from a second input source. The redundancy of these two input sources can be electronically identified and confirmed, and a warning can be generated for the operator. A further objective of the present invention would be to provide an inexpensive device for determining an objective pressure value generated when a drug is injected from a catheter using a manual syringe, in order to prevent the generation of excessive pressure at the catheter tip that could cause the catheter to deviate from its target position. The device of the present invention may allow the operator to set an audible warning for a maximum pressure value to warn if a certain pressure value is exceeded. Furthermore, a further objective may be to detect and display a pulsation pressure waveform corresponding to a cardiovascular pulse in order to determine the position of the catheter. A further objective of the present invention would be to provide a method and apparatus that can detect a pulsation pressure waveform present in the supradural space or spinal cavity of the central nervous system, and can detect the vicinity of a pulsation waveform or neurovascular bundle. Furthermore, in order to determine the patency of the catheter, objective pressure can be observed and graphed over time to observe the response when injection is performed using a manual syringe. Additionally, by simultaneously viewing the pressure / time graph and the pulsating pressure waveform, the objective pressure value and the pulsating pressure waveform can be correlated to determine the patency and position of the catheter, and to determine the function of the catheter. Moreover, the average value of the pulsating pressure waveform from the intravenous catheter can be provided to determine the patency of the catheter before, after, and during injection.

[0012] In particular, in a first exemplary configuration, the present invention can provide an apparatus for confirming the placement of a hollow structure at a desired treatment site in a mammalian subject. The apparatus may include a first sensor operably connected to a lumen located within the hollow structure, the first sensor being configured to provide a first signal in response to the detection of a first characteristic indicating heart rate in the lumen of the hollow structure. The apparatus may include a second sensor being configured to provide a second signal in response to the detection of a second characteristic indicating the heart rate. A control device may be operably connected (wirelessly or wired) to the first and second sensors to receive the first and second signals, and may be configured to compare the first and second signals and provide a comparison result, thereby providing an indication of the placement of the hollow structure to the desired treatment site. The first and / or second physical characteristics may be one or more of pressure, fluid volume changes, electrical signals, and optical signals. The first and second characteristics may relate to the same or different physical characteristics indicating the heart rate. The hollow structure may include one or more of an injection needle and a catheter. The first sensor may include a series pressure sensor having a sensor lumen arranged in fluid communication with the lumen of the hollow structure, and the second sensor may be a fingertip pulse sensor. One or more of the first and second sensors may each include a memory configured to store an indication that the first or second sensor has been used. The device may include an identification circuit embedded in or connected to one or more of the first and second sensors, the identification circuit configured to provide a signal to the control device, the signal including one or more of a configuration signal indicating the physical characteristics of the first or second sensor, a verification signal indicating the first or second sensor, and a usage signal so that the control device can detect the number of times or the length of time the first or second sensor has been used previously.

[0013] In a second exemplary configuration, the present invention can provide an apparatus for determining the placement of a hollow structure at a desired treatment site in a mammalian subject, comprising a control device configured to receive a first signal from a first detector located at the treatment site. The first signal may indicate a heartbeat within the hollow structure. The control device may also be configured to receive a second signal indicating the heartbeat from a second detector located at a second position. The control device may be programmed to compare the first and second signals and provide a comparison result, thereby providing an indicator of the placement of the hollow structure at the desired treatment site.

[0014] In both the first and second (or other) exemplary configurations, the first and / or second signals may represent one or more of pressure, fluid volume changes, electrical signals, and optical signals. The first signal may have a first period, and the second signal may have a second period, and the control device may be configured to compare the first and second periods to provide the comparison result. (Furthermore, 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 control device may be configured to compare the first and second periods to provide the comparison result.) Furthermore, the first signal may include a first numerical value indicating the frequency of the first signal, and the second signal may include a second numerical value indicating the frequency of the second signal, and the control device may be configured to compare the first numerical value and the second numerical value. One or more of the first and second numerical values ​​may be heart rate in beats / min. The control device may also be programmed to perform a cross-correlation analysis of the first and second signals. The control device may be configured to generate a warning signal if the comparison result falls within a selected range of values. Furthermore, a display may be operably connected to the control device to receive one or more of the first and second signals and the comparison result from the control device. In one preferred configuration, the control device may include the display. The display may include a first data section for displaying the pressure detected by the first sensor in the lumen located within the hollow structure, and a second data section for displaying the first and second signals. The first and second signals may each include their respective waveforms, 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 a warning when the comparison result falls within a selected range of values. The warning may be one or more of the auditory, visual, and tactile signals. [Brief explanation of the drawing]

[0015] The foregoing summary and the following detailed description of exemplary embodiments of the present invention can be further understood when read in conjunction with the accompanying drawings. [Figure 1] FIG. 1 is a diagram schematically showing an exemplary configuration of an apparatus for positioning a syringe needle or catheter according to the present invention, in which both a control device and a display device are used. [Figure 2] FIG. 2 is a diagram schematically showing a further exemplary configuration of the apparatus according to the present invention in which a separate control device is not used. [Figure 3] FIG. 3 is a diagram schematically showing additional aspects of the apparatuses of FIGS. 1 and 2. [Figure 4] FIG. 4 is a diagram schematically showing an exemplary configuration of a display of a prototype according to FIG. 1 of the present invention. On the display, objective pressure over time, heartbeat waves and pulse detected from two independent sources, together with clinically useful parameters of each of the two independent sources and real-time display of numerical pulse rate, are shown together with an indicator showing whether there is a correlation at that frequency (i.e., whether the two independent sources are both related to the heartbeat). [Figure 5] FIG. 5 is a diagram schematically showing details of an exemplary operation of the foregoing apparatuses of FIGS. 1 to 3. [Figure 6] FIG. 6 is a circuit diagram showing an exemplary configuration of the control device of FIG. 1. [Figure 7] FIG. 7 is a diagram showing a flowchart of an exemplary method of operating the apparatus of the present invention. [Figure 8] FIG. 8 is a diagram showing a method for performing signal correlation according to the present invention. [Figure 9] FIG. 9 is a diagram showing a further method for performing signal correlation according to the present invention. [[ID=三十二]] [[ID=三十三]] [[ID=三十四]]

Embodiments for Carrying Out the Invention

[0016] [[ID=三十八]] Referring now to the figures, like elements are numbered alike throughout, and FIGS. 1 and 2 illustrate exemplary configurations of devices 100, 150 of the present invention for determining an appropriate placement of a hollow structure, such as injection needle 302 and / or catheter 310, at a selected treatment site of patient 20, using at least two independent measurements of the heart pulse, one of which is detected through the hollow structure. For example, detection of the heart pulse through the injection needle 302 and / or catheter 310 may be accomplished by sensing a physical property in the lumen of the injection 302 and / or catheter 310, such as a physical property representative of a change in pressure or fluid volume in the lumen, the variation of the pressure or fluid volume change being caused by a cardiac systole, such as a heart pulse wave, and including a signal indicative thereof. In particular, a series pressure sensor 300 may be provided in fluid communication between the injection needle 302 (or catheter 310) and a manually held syringe 200, FIGS. 1 and 2.

[0017] The second of the two independent measurements may be detected by a second device, such as a fingertip pulse sensor 400, disposed at a location on the patient 20 where a physical property representative of the heart pulse can be detected (FIG. 2). The physical property may be, for example, pressure, an electrical signal, an optical signal, or any other suitable signal that provides an independent verification of the presence of the cardiac pulse detected by the injection needle 302 and / or catheter 310. The physiological location of the second device 400 may be different from the location of the injection needle 302 and / or catheter 310.

[0018] Through the use of two independent measurement sources 300, 400 for the heartbeat, the devices 100, 150 of the present invention can compare signals from the two separate measurement sources 300, 400 to confirm that the signal from the injection needle 302 and / or catheter 310 is indeed a heartbeat, which allows for confirmation that the injection needle 302 and / or catheter 310 is in the "correct" location for a procedure in which the target tissue is expected to have a heartbeat. For example, target sites for the correct placement of the injection needle or catheter where a heartbeat can be expected include the epidural space, the intrathecal cavity, or the vicinity of other anatomical structures that emit pulsating waves generated by the cardiovascular system, including neurovascular bundles or the heart itself.

[0019] Once the placement of the injection needle or catheter is confirmed by the devices 100, 150, a warning is provided to the clinician, who can then proceed with injection or aspiration via the syringe 200, depending on the nature of the procedure being performed. The warning may be provided in any appropriate form, such as auditory, visual, or tactile. Thus, the devices of the present invention enable positional guidance and confirmation during the placement of the injection needle 302 and / or catheter 310. In fact, the devices and methods of the present invention can confirm the patency of the injection needle 302 and / or catheter 310.

[0020] Looking at Figure 1 in more detail, the operation of the sensors 300 and 400 may be provided by a dedicated control device 500. The control device 500 may be operably connected to the sensors 300 and 400 via their respective cables 210 and 410, and in certain cases, an adapter 212 may be provided between the control device 500 and the respective cables 210. Alternatively, the sensors 300 and 400 may communicate wirelessly with the control device 500 via any suitable communication technology such as Bluetooth® communication. The sensor 300, which is arranged to communicate with the injection needle 302 and / or catheter 310, may be a series pressure sensor, such as Merit Medical, MER200, in which the fluid path is continuous with the injection needle 302 and / or catheter 310, as described above. In such a case, cardiac contraction results in the propagation of an energy wave representative of the heartbeat into the fluid within the sensor 300, and the energy wave may be measured through pressure or volume changes therein. The aforementioned changes may generate a repeating signal in the form of a pulse wave signal, and the frequency of the pulse wave signal can be determined by measuring from the maximum amplitude or zero crossing to obtain the heart rate of beats / minute. Alternatively, the sensor 300 can be positioned alongside the catheter 310 and / or interposed between it and an external fluid source such as an IV bag, syringe, or any container providing a continuous fluid line.

[0021] Furthermore, the sensor 300 (and / or sensor 400) may be one or more of the following: an acoustic sensor, an optical sensor, an infrared detector, or other devices that detect heartbeats propagating through tissue from the cardiovascular system to the location of the sensors 300, 400. In short, any type of sensor capable of detecting heartbeats within the lumen of the injection needle 302 and / or catheter 310 by pressure, acoustics, or other physical properties can be used as the sensor 300. Similarly, any type of sensor capable of detecting heartbeats from a physiological source independent of the lumen of the injection needle 302 and / or catheter 310 may be used as the sensor 400, including, for example, those based on photoplethysmography (PPG), such as Model 3231USB or Model 3230Bluetooth® Low Energy from Nonin® Medical, Inc. Alternatively, the sensor 400 may also be provided as a pneumatically inflatable blood pressure band (as found in blood pressure monitors). Since it is preferable to use a non-invasive method to detect the heart rate or pulses per minute of the peripheral vascular system, the detection of the heart rate may also be from an electronic signal captured by a heart rate monitor in contact with the patient's skin.

[0022] One or more of the sensors 300, 400 may also be provided in the form of a single-use sensor, which is considered particularly desirable when the sensors 300, 400 are in direct contact with body tissue or fluid, such as blood, cerebrospinal fluid, or an epidural space filled with fluid. For example, the sensor 300 may include a separate body fluid pressure sensor 305 and a microchip in the form of a programmable memory 320, Figure 3, the programmable memory 320 may be used to track the usage of the sensor 300 and thereby limit the sensor 300 to single use. Information communicated with the sensor 300 and memory 320 may be encrypted and coded to ensure the security of the use of the sensor 300. Alternatively or additionally, the sensor 300 may have an internal on-chip timer that allows for a specified time for the use of the sensor, after which the sensor 300 expires. These features help mitigate the possibility of use on multiple patients and help control against counterfeit products. The sensor 400 may be similarly configured for single use.

[0023] The data collected from the sensors 300 and 400 may be transmitted to the control device 500 for further processing, and the processed data may then be transmitted via cable 4 or wirelessly to a display device 600, such as a computer, smartphone, tablet, or other mobile terminal, for display by a clinician (Figure 1). The control device 500 may include a circuit board, a central processing unit, a rechargeable battery, a connector for wired communication, and / or an antenna for wireless communication by Wi-Fi, Bluetooth® or other suitable communication standard. The control device 500 may both process the received data, control the sensors 300 and 400, and supply power to them. The display device 600 may further process the data before display and may include various input elements such as buttons, touchscreens, voice activation commands, and scans to transfer information to the control device 500. Alternatively, the display device 600 may receive the data directly from the sensors 300 and 400 and control the operation of the sensors 300 and 400 so that a separate control device 500 is not required (Figure 2). In this regard, the display device 600 may include a software application that can collect, process, and display input data received from two or more separate input sources 300, 400, with or without using the control device 500. The data displayed by the display device 600 may include, but are not limited to, objective pressure values ​​630, a time-course graph of objective pressure 610, and a pulsation waveform 620 representing the contractility of the heart or cardiovascular system, as shown in Figure 2. A prototype of the control device 500 was built for use in the system 100 shown in Figure 1.

[0024] Prototype control device circuit Figure 6 is a schematic diagram of the circuit 550 used in the prototype control device 500 of Figure 1 (the circuit 550 also represents the implementation of the block diagram elements shown in Figure 3 at the component level; references to the corresponding elements in Figure 3 are provided in parentheses). As shown in Figure 6, two communication options are available and tested: wireless communication via Bluetooth® transceiver U2 (e.g., transceivers 532, 534, Figure 3) and direct wired communication via USB serial data cables 210, 410, Figure 1 connected to connector J1 in Figure 6 (the specifications of all components of the circuit 550 are listed in Table 1 below). The prototype 100 collects data from the two sensors 300, 400 and provides the data to the control device 500, which is formatted for presentation to the user.

[0025] In the prototype 100, the fingertip pulse sensor 400 used a Nonin® Medical, Inc. Xpod® 3012LP External OEM Pulse Oximeter with 8000A Reusable Finger Clip pulse oximetry sensor. The fingertip pulse sensor 400 generated a continuous stream of serial data input to connector J3. The data from the fingertip pulse sensor 400 was provided to unit serial input receiver channel 1 at pin 38 of microprocessor U3 (e.g., microprocessor 520, Figure 3). Standard baud rate transmission, set by resistor R16, was used. The data was collected and assembled into a simplified format for use by the display device 600.

[0026] The series pressure sensor 300 was a model MER200 of Merit Medical, Inc.'s piezoresistive bridge design and was mounted on connector J4 in Figure 6. The reference voltage used to power the series pressure sensor 300 was supplied directly from the lithium-ion battery BT1 of the circuit 550. The series pressure sensor 300 was connected via adapter 212 (Figure 1). The adapter 212 had the function of easily connecting the sensor 300 to the control device 500 via an RJ12 quick connector J12, a power-on function by interlocking connection to the battery BT1, and a function of identifying and managing the use of the series pressure sensor 300 by one-wire memory.

[0027] A memory device 320 may be present in the series pressure sensor 300 in Figure 3 to identify and serialize the series pressure sensor 300, enabling the display device 600 to collect and store traceable data. In the prototype, such a memory device was located in the adapter 212. The use of the memory device 320 also helps mitigate the possibility of using the pressure sensor 300 for multiple patients. The sensor 3003 and adapter 212 in Figure 1 may be disposable components intended for single use on one patient.

[0028] Since the device 100 had a user-accessible connector J4, the circuit 550 included protection against electrostatic discharge (ESD) events caused by excessive static charge accumulation. Diodes D4-D9 were used to clamp the input of connector J4 and protect the internal circuit (Figure 6). The adapter 212 internally jumper-coupled pins 4-5 at connector J4 in Figure 6, providing a connection path from the negative terminal of the internal battery BT1 to the remaining components of circuit 550. Thus, when the adapter 212 was attached to the connector J4, power was supplied to the circuit 550, thus reducing the leakage current exposure to the user or patient that would occur without the adapter. The connector J4 was also used to charge the battery BT1 using an external charger 10 attached to J4 via cable 2 (Figure 1). When the charger 10 was attached, power was not supplied to the circuit 550, and only the battery BT1 was charged. Protection against battery failure / fire was provided by limiting and monitoring the charging current.

[0029] As shown in Figure 6, the signal from the series pressure sensor 300 was presented to a chip U4 (e.g., A / D converter 510, Figure 3), which is a high-resolution 24-bit analog-to-digital converter. The analog-to-digital converter U4 used the same battery / ground voltage that powered the series pressure sensor 300 for its reference voltage. Thus, the analog-to-digital converter U4 performed measurements proportional to the supply voltage of the signal from the series pressure sensor 300, and no correction for gain and offset was required. The raw output of the analog-to-digital converter U4 was multiplied by a constant determined by the gain of the Merit MER200, which was pre-calibrated and adjusted at the time of manufacture. Resistors R14 and R15 of the circuit 550 provided mitigation against possible breakage of the sensor leads for the series pressure sensor 300. In the event of a break, the pressure measurement from the analog-to-digital converter U4 would be driven to the upper or lower limit and thus invalid.

[0030] The data from the analog-to-digital converter U4 was transmitted to the microprocessor U3 via a serial peripheral interface (SPI) serial channel. The data from the analog-to-digital converter U4 was assembled into 3 bytes, which were then reassembled in the microprocessor U3 as a 32-bit word representing the catheter 310 / needle pressure.

[0031] The microprocessor U3 stored several pieces of data, including the device serial number, catheter gain correction, and general hardware settings, in non-volatile memory. This data was transferred and modified by commands sent from the display device 600. This information was stored in the EEPROM memory built into the microprocessor U3.

[0032] While collecting the series pressure sensor data from the analog-to-digital converter U4, the microprocessor U3 also attempts to measure the electrocardiogram lead pulse rate if it is present in the waveform signal from the series pressure sensor 300. The average value of the waveform signal is calculated and subtracted from the raw data to obtain a zero-core waveform. The zero-core waveform is processed to identify the zero crossings of the zero-core waveform and to determine the periods of the peaks and troughs. The periods from the maximum and minimum are measured and converted into a numerical value of pulses per minute. The numerical value and the positive zero crossing information are transmitted to the display device 600 via a communication channel. Additional details regarding the operation of the microprocessor U3 will be described later in relation to Figure 8.

[0033] As shown in Figure 6, the clock source for the microprocessor U3 was a crystal oscillator Y1. The selection of the frequency established the internal timing measurement and communication speed. The frequency was chosen to obtain sufficient processing speed while suppressing radiated interference from the circuit 550. The voltage of the 3.7V battery BT1 also helped to reduce radiation. The voltage divider consisting of R1 / R2 and R9 / R10 scaled the voltages from the battery BT1 and the wireless transceiver U2 to a value within the range of the analog-to-digital converter built into the microprocessor U3, enabling measurement of the power supply voltage. This design was capable of operation with a battery voltage of 3.0 volts or less. Continuous operation for more than 12 hours was possible before the battery needed to be recharged.

[0034] The microprocessor U3 was programmed in-circuit using a standard programmer from Microchip Technologies mounted on J2. The software design includes a bootloader portion, allowing the code to be modified in the field. After the initial programming, the production jumper JP2 allows solder connections to be placed across the circuit 550 to protect it from future programming. The jumper JP2 also improves protection against ESD events.

[0035] The circuit 550 included two options for communication with the display device 600. When the USB cable option was used, a Future Technologies Digital International (FTDI) serial-to-USB cable 4, Figure 1, was connected to the "b" side, i.e., jumper J1 on pins b2-b7. This connected the cable 4 directly to serial channel 2 of the microprocessor U3. The USB cable option was configured as a full implementation of RS-232 (TTL) using flow-controlled CTS / RTS. The smart USB cable 4 was powered by the display device 600, to which the USB connection was made. Power was not supplied via the circuit 550. In the display device 600, the USB port was configured as a virtual communication serial port.

[0036] Bluetooth® wireless communication was implemented by removing the FTDI cable 4 and placing a jumper between pins 3-8 and ab of jumper J1. The communication baud rate was selected based on the initial settings of the Bluetooth® transceiver U3. The same baud rate was used for the FTDI USB cable. This allowed the microprocessor U3 to operate regardless of whether information or commands were transferred from the display device 600 via USB communication or Bluetooth® communication.

[0037] The wireless transceiver module U2 was a microchip design that simulated serial communication with the display device 600 and was pre-certified to meet FCC and EU standards requirements for RF performance. The green LED D2 indicated that the wireless transceiver module U2 was powered, and the red LED D3 blinked during data transmission (Figure 6). The mode jumper JP1 was normally shorted and used only for debugging. The monitoring circuit U1 powered on and shut off the wireless transceiver module U2 during low-voltage operation. The display device 600 was responsible for pairing and connecting the wireless transceiver module U2 with the transceiver antenna AE1. The operation of the transceiver U2 was performed according to the frequencies and protocols defined for Bluetooth® BLE. The wireless transceiver module U2 was defined as a server device that provided data to slaves. The wireless transceiver module U2 communicated wirelessly with the display device 600, or in the case of the prototype, a tablet (Dell® Latitude 7200, a 2-in-1 tablet), and ran software to analyze and display signals from the two sensors 300 and 400.

[0038] [Table 1]

[0039] display device More specifically, regarding the display device 600 and signal analysis, the display device 600 can generate data and warnings useful to clinicians to assist in the placement of the injection needle 302 and / or catheter 310, either alone or in cooperation with the control device 500, including providing an indication of the patency of the catheter 310 (Figures 2, 4). Figure 4 schematically shows an actual screenshot of what the display device 600 provides as used in a working-level prototype 100 of Figure 1, which includes the control device 500 having a control device circuit 550. Figure 4 simply provides one exemplary data output configuration according to the present invention.

[0040] Referring to Figure 4, the display 450 on the liquid crystal screen of the display device 600 contained two graphs. The upper half of the screen displayed an "objective pressure graph" 451, and the lower half displayed a "pressure waveform graph" 455, displaying waveforms 452 and 453 corresponding to the data collected from the sensors 300 and 400, respectively. Furthermore, a dialog bar was provided below the pressure waveform graph. These two graphs could be displayed simultaneously or individually with a time delay.

[0041] The objective pressure was displayed in Figure 4 both as an objective pressure graph showing objective pressure versus time in a scroll graph 451 and as a real-time numerical value 401. A maximum pressure line was also displayed, which could be modified by the clinician. If the objective pressure exceeded this line, an alarm sounded, although the alarm could have been visual or of other types. The objective pressure 401 corresponds to the pressure generated by the handheld syringe 200 when the clinician applies force to the plunger of the syringe 200. The graphing of the objective pressure data was performed continuously in real time, and the scaling could be changed in real time by pressing the up and down arrows (↑, ↓) in the left sidebar of the objective pressure graph 451. If it was detected that the pressure had reached the maximum pressure line without fluid flow, the clinician could conclude that the injection needle 302 and / or catheter 310 were occluded. A negative slope in the objective pressure graph indicates pressure dissipation in the injection needle 302 and / or catheter 310, and further indicates that the injection needle 302 and / or catheter 310 are not occluded. Thus, even when the data of the waveforms 452 and 453 are ambiguous, the real-time changes in the objective pressure graph provide important information for confirming or ruling out occlusion of the injection needle 302 or catheter 310. Therefore, the objective pressure graph provides information on the patency of the injection needle or catheter in addition to the information displayed in the waveforms 452 and 453.

[0042] The pressure waveform graph 455 was constructed using a high-resolution, high-speed sampling algorithm that performs sampling 30 to 90 times per second. In the prototype, the average value of the waveforms 452 and 453 was calculated and displayed on the display device 600, and the waveforms 452 and 453 were kept in the center of the pressure waveform graph. Within 4 seconds (or other periods programmed by the software), the waveforms 452 and 453 were calculated to be the average pressure values ​​and positioned in the center of the graph 455 relative to the average horizontal line 454 displayed in Figure 4.

[0043] The waveforms 452 and 453 from the first and second sensors 300 and 400 had peaks (and zero crossings) of maximum amplitude that reflected the pulsity of cardiac contraction and were consistent with the beats per minute (bpm) value. It is also possible to calculate the heart rate from the zero crossings in beats per minute. However, since there are two zero crossings for each heartbeat, either the time between consecutive positive slope zero crossings or the time between consecutive negative slope zero crossings will represent the heart rate. The two waveforms 452 and 453 are visually compared by the clinician on the display 450. In addition, the real-time value 402 of the heart rate detected by the first sensor 300 and the real-time value 404 of the heart rate detected by the second sensor 400 were displayed (Figure 4). Detection of both waveforms 452 and 453 from the two input sources 300 and 400 provides the clinician with an understanding of the location of the injection needle 302 and / or catheter 310 within anatomical structures that transmit pulse waves from the cardiovascular system. Two sets of up and down arrows (↑, ↓) in the left sidebar of the pressure waveform graph could be used to individually scale the height of each of the waveforms 452 and 453. Furthermore, it was possible to provide a bpm beep sound that sounds at the same frequency as the pulse rate shown in either waveform 452 or waveform 453. In such a case, it is also possible to omit the display of the waveforms 452 and 453 associated with the audible bpm beep sound, and the audible bpm beep sound may serve to provide such information to the clinician.

[0044] Alternatively, the waveforms 452 and 453 can be displayed in a variety of different formats. Exemplary formats include (but are not limited to) a continuous waveform where the maximum amplitude is represented as a continuous pressure waveform, a discontinuous line where the maximum amplitude is displayed, or a flashing light representing the maximum amplitude pressure value detected by the input source. Furthermore, instead of both waveforms 452 and 453 being displayed, only a visual warning is provided to confirm that the signal is being adjusted with the maximum amplitude signal representing the pulses / minute from the two independent sources 300 and 400. For example, neither waveform 452 nor 453 can be displayed, and the maximum amplitude signal can be represented as an audible or tactile signal. Alternatively, it is possible to rely solely on the numerical value displayed as pulses / minute. Furthermore, any combination of these display techniques can be used.

[0045] As shown in Figure 4, the dialog bar includes (from left to right) 1) a "Zero" button for calibrating the series pressure sensor 300, 2) an objective pressure value 401 for the series pressure sensor 300, 3) a heart rate beats per minute (bpm) 402 from the series pressure sensor 300, 4) a "Sync alert" 403 indicating that the heart rate values ​​402 and 404 have been correlated to confirm that a single source (heart) produced both of these signals, 5) a heart rate beats per minute (bpm) 404 from the fingertip pulse sensor 400, 6) an oxygen saturation value 405 in percent, and 7) an "image" button for capturing an image on the screen.

[0046] The display device 600 of the prototype performs an analysis to determine whether the two waveforms 452 and 453 are correlated at a fundamental frequency corresponding to the heart rate bpm (beats / minute) when the waveforms 452 and 453 represent the heart rate. Otherwise, the fundamental frequency would correspond to other spurious signals unrelated to the cardiovascular system. The two signals were considered to be correlated in frequency even if there was a phase offset between the two signals, as shown in the waveforms 452 and 453 of Figure 4. A phase offset between the signals may exist because the heart rate may travel through different tissue types and over different distances to reach each of the sensors 300 and 400.

[0047] If the waveforms 452 and 453 are frequency correlated, the "Sync alert" 403 flashes on / off to alert the clinician that the bpm rates from each of the sensors 300 and 400 have been found to be correlated, i.e., that the frequencies of the signals from the sensors 300 and 400 have matched sufficiently within a selected range of deviation, with an acceptable range of deviation being 2 bpm to 15 bpm. Thus, when the "Sync alert" 403 is activated, the clinician is provided with confirmation that the injection needle 302 / catheter 310 is positioned in the desired location. Furthermore, if the two waveforms 452 and 453 are not correlated, a warning may optionally be sounded indicating that the injection needle 302 / catheter 310 is not properly positioned. Any of these warnings may be visual, auditory, tactile, or any combination thereof.

[0048] Furthermore, the signals detected by the sensors 300 and 400 can be analyzed by various correlation techniques, including but not limited to waveform analysis, pulse rate comparison (heart rate, beats / minute), cross-correlation, and combinations thereof, to determine the heart rate. In yet another embodiment, cross-correlation analysis can be performed on the data from the sensors 300 and 400 to generate matched frequencies of the two signals with time shifts that produce a clear positive correlation based on a set criterion. In this case, the cross-correlation may be the sum of the products of the two signals that have been shifted relatively over a period of one or more full cycles of the waveform of the longer period. In yet another embodiment, autocorrelation is used to normalize the cross-correlation peak values ​​for better threshold detection comparison. In yet another embodiment, the autocorrelation peak interval is used to validate the BPM measurements made for each sensor data.

[0049] In yet another embodiment, cross-correlation analysis may be performed on the data from the two input sources 300, 400 that produce a definitive positive correlation based on a set criterion. Figure 9 shows an example of the cross-correlation technique according to the present invention, used to objectively determine the degree of correlation between the two signals 452, 453 from sensors 300, 400. Exemplary details are specific to the implementation for the control devices 500 and 600. For discontinuous data samples such as those collected by the exemplary devices 100, 150 of the present invention, the cross-correlation function is defined as follows:

[0050]

number

[0051] Here, T is the period (number of samples) of the waveform being analyzed, and τ is the sliding offset between the two waveforms.

[0052] Essentially, the correlation function generates a series of sums of products over the entire sampled dataset to calculate the value of the correlation coefficient for each τ value. The calculated correlation coefficient has a maximum value at shift τmax. Due to possible velocity propagation delays through patient tissue, the two waveforms 452, 453 may have an offset in the peak correlation coefficient position where τmax ≠ 0. Method 900 shown in Figure 9 represents an exemplary method used for correlation detection according to the present invention. Data collected from the series pressure sensor 300 is input in step 902. The pressure measurements from the fingertip pulse sensor 400 are input in step 904. The data is collected synchronously by the display device 600, and therefore the set of data (902, 904) represents a single process in time. The sampled data is placed in circulating FIFO buffers 906, 908. The size of the buffers 906, 908 is determined by the period of the pulse waves 452, 453. The longest period occurs at the lowest pulse rate, defined as 40 BPM. With a data sampling frequency of 75 samples / second, a minimum of 112 samples represent one complete waveform in each buffer 906, 908. Furthermore, the τ shift is similarly limited to a maximum of 112 samples. Therefore, the minimum buffer size for performing the complete cross-correlation function is 224 for the combined buffers 906, 908. In this exemplary case, the buffer length may be chosen as 256, which facilitates cyclic FIFO buffer management and also provides some additional space for the buffers 906, 908. An extra 32 buffer positions (256-224=32) may be provided to allow new data to be inserted into the cyclic buffers 906, 908 without destroying the 224 value being processed to determine the correlation coefficient. The buffers 906, 908 can be written to and read simultaneously, easing the computational burden on the microprocessor in the display device 600. The calculations do not need to be completed within a single data sample time. Word correlation is generally a serial process of mathematical operations. Each new correlation check starts at the position of the last data written to the aforementioned circular buffers 906, 908 and operates in reverse.

[0053] The correlation algorithm 902 may start from the last data position written and work backward through the data from this point. Based on the buffer size and assumed pulse rate, the complete calculation must be completed before 32 additional data samples are taken, i.e., 32 samples / 75 samples / second, or 0.43 seconds. During this time, 112 multiply-accumulate operations are performed. The multiply-accumulate operation step 914 multiplies the 112 multiplication values ​​910a to 910d of the data in each buffer 906, 908. Each correlation coefficient calculated at the multiply-accumulate operation point 914 may be temporarily stored in an array buffer 918. Each value stored is the sum of products of the τ parameter over 112 offsets. The τ offset is the starting point from which data is read from the buffers 906, 908 for each multiply-accumulate operation. The results in the array buffer 918 may be analyzed to determine the degree of the correlation between the pulse waves. Autocorrelation may also be performed to normalize the results of the cross-correlation. Numerically, the cross-correlation result of buffer 918 is preferably between +1.0 and -1.0. Values ​​close to 0.0 are considered uncorrelated and are displayed as "Not In-Sync" on the display device 600. Values ​​greater than the determined threshold are considered significantly correlated and provide the clinician with instructions for the correct placement of the injection needle 302 and / or catheter 310. The pulse rate should be greater than the minimum design value, and multiple correlation coefficients will be generated. For example, at a pulse rate of 80 BPM, there will be two maximum correlation values. The correlation algorithm 920 may analyze the data for the maximum peak and generally select a τ offset value close to zero. All of the selected correlation coefficients may be output to the display device 600. The analysis may include considering the measured BPM from each sensor 300, 400. The BPM may also be obtained by analyzing the autocorrelation measurements performed for each waveform 452, 453. While it may lack resolution detail, the separate measurement of the multiple peaks of the autocorrelation, which is another measurement of pulse rate from each sensor 300, 400, may provide useful information for performing the correlation detection display.

[0054] Control system algorithm In another embodiment, the apparatus of the present invention can be used to verify the placement and patency of a catheter or injection needle (Figure 8). The flowchart in Figure 8 represents the software logic used in the prototype to calculate the pulse rate per minute measured by the serial pressure sensor 300. The software was executed in the microprocessor U3 (Figure 6) of the circuit 550 of the control device 500. The software identified the zero crossings of the cardiac pulse wave signal 452 in the injection needle 302 and / or catheter 310 (Figure 40). The pulse rate per minute was determined by measuring the period between consecutive positive zero crossings of the pulse wave signal 452. The positive zero crossings were selected because the ascending aortic systolic pressure wave has a faster rate of change and therefore provides a more accurate measurement point than the downward slope of the negative zero crossings. The software operated in loop 867 with a state machine to analyze the pulse wave 452.

[0055] The state machine was initialized in step 851, which initiated the execution of the software (Figure 8). The STATE variable determined which side of the mean the loop 867 had processed last. A filter counter variable was provided, which was increased and decreased based on whether the difference between the measured value and the mean was greater than or equal to zero or less than or equal to zero. Also in step 851, the moving average filter was initialized. In step 852, the pressure measured value was obtained from the analog-to-digital converter U4 in Figure 6. The analog-to-digital conversion was generated by a hardware event and occurred at approximately 80 samples / second. The new value of the pressure sample was obtained in step 852 and sent to the display device 600. The new pressure sample was also used in method 850. Specifically, the new pressure sample was added to the moving average filter by calculating the moving average in step 853. The moving average filter output the average value of the past 128 pressure samples. In step 854, the pressure sample was subtracted from the average value to generate the difference value saved in step 855. Next, in step 856, a determination was made to determine whether the previous operation was looking for a positive (POS) or negative (NEG) zero crossover. If the STATE in step 856 was POS, the software branched to step 862 to look for a negative crossover. The criterion for a negative crossover was that the difference was less than (more negative than) -0.1 mmHg, which is a negative threshold. If the difference did not meet this criterion, the loop passed to step 866, where it waited for the next pressure sample and repeated the process of method 850 through step 860. Returning to step 862, if the difference met the criterion, the filter counter was decremented to step 863. In step 864, the calculated value was tested to determine whether the calculation was less than -3. If not, control passed to step 866, and method 850 was repeated by passing to step 866 and waiting for the next sample. Typically, the final value of the filter counter is +4 following the last positive zero crossover. Therefore, the filter counter must be decreased eight times to reach the tested value -4, and then the STATE variable is set to NEG, indicating that a descending zero crossing has been found, and the process proceeds to step 865.The filter counter value was forced not to exceed 4. The loop 867 was then returned to await the next pressure sample in step 866.

[0056] Returning to step 856, if the STATE in step 856 is NEG (i.e., not POS), i.e., looking for a rising zero crossing, the branch would continue to step 857. In step 857, a test was performed to determine whether the criterion for a positive zero crossing was met. The differential pressure must exceed +0.1 mmHg. If not, method 850 jumps to step 866 and repeats, waiting for another pressure sample. The criterion should be met, and control is passed to step 857. The filter counter value was incremented in step 858. Typically, the counter starts increasing from -4 after the last falling zero crossing. In step 859, the count value was tested to determine whether a sufficient positive difference was found to justify the display of a rising zero crossing of pressure, i.e., whether the count exceeded +3. If not, control is passed to step 866, and method 850 is passed to step 866 and repeated by waiting for the next sample. If the filter counter exceeds +3 in step 859, control is passed to step 860. In step 860, the STATE variable is set to POS, and the filter counter is limited to +4. At this point, a valid positive zero crossing is determined. The algorithm measures the period since the last positive zero crossing occurred. The period is measured in milliseconds by a time reference maintained by the microprocessor U3 using interrupts. The period measurement is dynamically adjusted to provide good BPM measurement. For fast heart rates of 200 BPM or more, up to four zero crossings are counted to achieve a resolution better than 1.0 BPM. For low pulse rates of 60 BPM or less, a single zero crossing period measurement is performed to allow for rapid updating of the measured heart rhythm. The final calculation of the period is performed in step 861, and the calculated BPM value, 402 in Figure 4, is sent to the process control unit 600 for display to the user and pulse correlation matching with the heart rate 404.

[0057] Further understanding of how the devices 100 and 150 of the present invention may operate in relation to generating the data to be displayed on the display device 600 can be seen in block diagram 800 of Figure 5. In this diagram, the "cardiovascular pulse sensor device" block corresponds to the sensor 400, and the "pressure sensor device" block corresponds to the sensor 300. Furthermore, while the communication between the components and processes is illustrated using wireless communication with conventional Bluetooth® communication symbols, communication by other methods such as Wi-Fi or wired connections is also possible.

[0058] Application software 803 that can run on the display device 600 may include the step 804 for writing a time / date stamp on the sensor 300 to help ensure that the sensor 300 is used only once. As part of the operation, the software also acquires the data from the sensors 300, 400 in step 805. Data acquisition continues until completion (step 806), and the Bluetooth® radio is disabled (step 807). During the data acquisition step 805, subprocess 808 is an executable process that includes functions such as creating a graph display of the pressure 810, calculating an overpressure warning 811, displaying a numerical pressure 812, performing correlation detection of the data received from the sensors 300, 400 in step 813, and issuing various warnings 814.

[0059] Furthermore, the authentication method of the present invention may include a computer chip, SIM, or other uniquely coded circuit, such as chip 320, in the adapter 212 or sensor 300. The chip, SIM, or other uniquely coded circuit may be located in communication with the control device 500 and / or display device 600 and can be read by an authentication program or circuit within the control device and / or display device 500, 600. If the chip, SIM, or other uniquely coded circuit is authentic, the control device and / or display device 500, 600 will operate properly; otherwise, it will disable the sensor 300 and display a warning on the display device 600 such as "Unauthorized Adapter Detected," and optionally emit a warning sound, but not limited to a spoken word, an alarm, or other warning signal or any combination thereof. The coded circuit may also be coded for a one-time function in which the authentication program or circuit within the control and / or display device 500,600 detects whether a particular sensor 300 has been used previously, and if so, disables the control and / or display device 500,600 again and posts a warning.

[0060] Exemplary Method Description In another embodiment, the apparatus of the present invention can provide a clinician with a particularly useful method for verifying the position and patency of a catheter or injection needle, such as method 700 illustrated in Figure 7. For example, a clinician often needs to determine, collectively starting from step 702, whether a catheter is i) clogged or functioning, and / or iii) whether the catheter has moved from its target position. To make such a determination, the following actions may be required: 1) flush the catheter to determine whether it is clogged or not, and then 2) inject a bolus of medication. When making such a determination, the clinician may connect a series pressure sensor between the catheter and a syringe used to flush the catheter, and, in step 704, attach a secondary input source, such as a photoelectric fingertip opening / closing mechanism, to detect a heartbeat. The syringe and series pressure sensor, as well as other disposable instruments such as the catheter, may be prepared with fluid (step 706). The series pressure sensor and secondary source may be wired or wirelessly operable to a display device for the clinician to view (step 708). The maximum objective pressure value may also be set in the handheld device and stored in the handheld device for future use. The maximum pressure value may be set to any value between, for example, 75 mm / Hg and 500 mm / Hg. When the maximum pressure value is reached, a warning may be sounded as an audible sound or tone. Spoken language may also be used to inform the clinician that the maximum pressure has been exceeded.

[0061] The signals from the series pressure sensor and the secondary source (e.g., a fingertip pulse sensor) may be compared and analyzed by a control and / or display device, such as one or more of the control device 500 and the display device 600. If the two signals are found to be correlated in frequency (i.e., heartbeats / minute), a warning box indicating that the catheter is properly positioned may be displayed on the display device as a flashing box and / or an audible warning may sound.

[0062] If a pulse wave is detected (step 710), the clinician may proceed to clean the catheter (step 712). The clinician may again observe the response on the display device (step 714). If no response is observed and no pulse wave correlation is found between the signal from the series pressure sensor and the secondary input source, step 722, the pulse wave detected in step 710 (or step 732 described below) is a false positive. The clinician then concludes that the catheter is not properly positioned and removes the catheter (step 724). Alternatively, if a response is observed in step 714 and the clinician observes a pulse wave correlation between the signal from the series pressure sensor and the secondary input source, step 716, the clinician may administer a bolus of drug to the patient, step 718, and observe the therapeutic output, step 720.

[0063] Returning to the situation in step 708 where no initial response is observed, the clinician can observe an objective pressure graph to determine the patency of the catheter. In such a case, the clinician is likely to see no pulse wave detected at all, but will still proceed with flushing the catheter (step 728). In this case as well, the clinician can observe the response on the display device (step 729). Next, the clinician can determine whether the catheter is clogged by observing that there is no decrease in the pressure, which can be observed by looking at an objective pressure-for-time graph where the slope of the curve demonstrates whether fluid is flowing out of the catheter into the tissue. If the pressure does not dissipate over time, step 736, and if no pulse wave correlation is found between the signal from the series pressure sensor and the secondary input source, step 738, the clinician can conclude that the catheter is clogged and can be removed, step 740. Alternatively, if a response is observed in step 729 and the response is a pressure drop, in step 730, the clinician may observe that a pulse wave correlation is found between the signal from the pressure sensor and the secondary input source, in step 732. In such a case, the clinician may proceed with rinsing the catheter, in step 734, proceeding with steps 714 through 724 as described above. Although the examples in the following sections describe a method for use with a catheter, it will be understood that similar methods can be used for the placement of an injection needle in a patient, which is performed in the same procedure as described.

[0064] Method 700 is expected to be used, for example, to confirm the position of a catheter in the epidural space or intrathecal cavity. Furthermore, Method 700 can be used to determine if an injection needle or catheter is properly positioned for infusion within a blood vessel such as a vein or artery. Such a system could also be used for aspirating bodily fluids where the position of the injection needle within a target, confirmed by a pulsation waveform, is required prior to the removal of the fluid, such as cerebrospinal fluid, from the central nervous system. Method 700 can also be used in situations where it is essential to evaluate the pulsatility of tissue. The apparatus and method of the present invention can also be used to evaluate the perfusion state of blood vessels to tissues or organs based on the quality (amplitude and frequency) of the pulsation pressure waveform, such as the pulse interval and amplitude of the waveform curve, for example, to evaluate the perfusion state in limbs associated with diabetes, frostbite, trauma, tissue transplantation, etc.

[0065] Accordingly, the above disclosure describes an apparatus and method that can confirm the location of an injection needle and / or catheter, as well as the patency of a properly positioned indwelling catheter. The apparatus and method can essentially confirm, by physiological feedback, that the injection needle or catheter is positioned within an anatomical site. The apparatus according to the present invention can detect the presence of cardiovascular signals from two separate input sources and determine whether the signals are coordinated by analysis of the signals. If a positive correlation is confirmed, the location of the injection needle or catheter in the body can be confirmed, and a warning may be provided accordingly. If a correlation cannot be established between the two cardiovascular signals, no warning is provided, which indicates that the injection needle and / or catheter is improperly positioned.

[0066] 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 to those skilled in the art that changes or modifications can be made to the embodiments described above without departing from the broader concept of the invention. For example, the apparatus disclosed herein can incorporate a device for remotely monitoring a patient by Bluetooth, Wi-Fi, or other device that transmits the collected pressure data to software loaded on a smartphone or computer workstation. A clinician could then assess the patient's condition in relation to the presence or absence of pulsation waveforms. A communication module optionally present in the control device 500 and / or the display device 600 can relay the collected data to either an online external communication system or a specific communication target for relaying this information for either immediate or retrospective review. Accordingly, it should be understood that the present invention is not limited to the specific embodiments described herein, but is intended to include all changes and modifications that fall within the scope and spirit of the invention as defined in the claims.

Claims

1. A device (100, 150) for confirming that a hollow tubular structure (302, 310) is located at a desired treatment site on a mammalian subject, A first sensor (300) is operably connected to the lumen of the hollow tubular structure, the first sensor being configured to provide a first signal in response to the detection of a first characteristic indicating a heartbeat within the lumen of the hollow tubular structure, the hollow tubular structure having one or more of an injection needle and a catheter, the first sensor and A second sensor (400) configured to provide a second signal in response to the detection of a second characteristic indicating a heart rate, wherein the second sensor has a fingertip pulse sensor, and the second sensor Control devices (500, 600) that are operably connected to the first and second sensors (210, 212, 410) and receive the first and second signals, It has, The control device is configured to compare the signal waveforms of the first and second signals, calculate their correlation, and indicate that the hollow tubular structure is located at the desired treatment location if the correlation is higher than a predetermined threshold. A device characterized by the following features.

2. The apparatus according to claim 1, wherein the first sensor is arranged in fluid communication with the lumen of the hollow tubular structure, and the first sensor has an in-line pressure sensor (300).

3. The apparatus according to claim 1, wherein the first and / or second physical characteristic is one or more of pressure, fluid volume change, electrical signal, and optical signal.

4. The apparatus according to claim 1, wherein the first and second characteristics relate to either the same physical characteristic or to different physical characteristics.

5. The apparatus according to claim 1, further comprising an identification circuit (550) incorporated into or connected to one or more of the first and second sensors, wherein the identification circuit is configured to provide a signal to the control device, the signal including one or more of a setting signal indicating the physical characteristics of the first or second sensor, a verification signal indicating the first or second sensor, and a usage signal for enabling the control device to detect the number of times or the length of time the first or second sensor has been previously used, and each of the first or second sensors includes a memory (320) configured to store an indication that the first or second sensor has been used.

6. The apparatus according to claim 1, wherein the first signal has a first period, the second signal has a second period, and the control device is configured to provide the correlation by comparing the first and second periods.

7. The apparatus according to claim 1, wherein the first signal consists of a waveform (452) having a first period, the second signal consists of a waveform (453) having a second period, and the control device is configured to provide the correlation by comparing the first and second periods.

8. The apparatus according to claim 1, wherein the control device is configured to determine whether the first and second signals are correlated and to provide the correlation degree.

9. The apparatus according to claim 1, wherein one or more of the first and second signals each have waveforms (452, 453) each having their respective period and respective average values, and the control device is configured to detect the zero core of each waveform passing through the respective average values.

10. The apparatus according to claim 1, wherein the control device is configured to generate a warning signal (403) when the correlation is within a predetermined threshold.

11. The apparatus according to claim 1, comprising a display (450, 600) operably connected to the control device and receiving one or more of the first and second signals and the correlation from the control device, the display including a first data section for displaying pressure versus time (610) in the lumen of the hollow tubular structure, and / or a second data section for displaying the first and second signals, the second data section including a graph displaying the respective waveforms of the first and second signals as a function of time, the display including a section for displaying a warning when the correlation is within a predetermined value, the warning (814) including one or more of the auditory signal, visual signal, and tactile signal.

12. The apparatus according to claim 1, wherein the control device is programmed to perform a cross-correlation analysis (900) of the first and second signals.

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