Patent Description:
Pulmonary artery catheters, also known as Swan-Ganz catheters, can be advanced into the pulmonary artery of a patient to continuously monitor hemodynamic variables. Pulmonary artery catheters allow for the continuous sensing of flow, pressure, and oxygenation delivery and consumption. Specifically, pulmonary artery catheters can be used to determine the following hemodynamic variables: cardiac output (the volume of blood being pumped by the heart per unit of time), mixed venous oxygen saturation (measure of the relationship between oxygen delivery and oxygen consumption), stroke volume (the volume of blood ejected from the ventricle in each beat), systemic vascular resistance (the resistance that must be overcome to push blood through the circulatory system), right ventricular ejection fraction (the percentage of blood ejected from the ventricle with each beat), right ventricular end diastolic volume (the volume of blood in the ventricle at the end of the diastole), right atrial pressure (the blood pressure in the right atrium of the heart), pulmonary artery pressure (the blood pressure in the pulmonary artery), pulmonary artery occlusion pressure (an estimate of the blood pressure in the left atrium) (also known as the pulmonary wedge pressure), and diastolic pulmonary artery pressure (the blood pressure in the pulmonary artery at the end of the diastole).

The hemodynamic variables that are determined with pulmonary artery catheters can help in the diagnosis, monitoring, and treatment of the following: acute heart failure, severe hypovolemia, complex circulatory situations, medical emergencies, acute respiratory distress syndrome, gram negative sepsis, drug intoxication, acute renal failure, hemorrhagic pancreatitis, intra and post-operative management of high risk patients, history of pulmonary or cardiac disease, fluid shifts, management of high-risk obstetrical patients, diagnosed cardiac disease, toxemia, premature separation of placenta, cardiac output determinations, differential diagnosis of mitral regurgitation and ventricular septal rupture, and diagnosis of cardiac tamponade. Pulmonary artery catheters can also be used to monitor hemodynamic variables during the following procedures: coronary artery bypass graft, aortic valve replacement/repair, mitral valve replacement/repair, aortic valve conduit, aortic arch replacement, cardiogenic shock, acute mitral regurgitation, ventricular septal rupture, and pulmonary artery hypertension.

Pulmonary artery catheters are advanced to a patient's right atrium and an inflatable balloon at a distal end of the pulmonary artery catheter is inflated in the right atrium. The inflatable balloon then floats through the patient's right atrium and right ventricle and will wedge in the pulmonary artery. One of the risks associated with advancing a catheter into the pulmonary artery is looping and knotting of the catheter inside the body. Patients with low blood flow are more susceptible to knotting of the catheter because the catheter is less able to follow the expected trajectory of blood flow through the right atrium and right ventricle into the pulmonary artery. When the catheter does not follow the expected trajectory, it can start coiling and forming one or more loops (most likely in the right atrium or right ventricle of the patient). Eventually, knotting can occur when the catheter is pulled. When knotting does occur, a procedure is needed to undo the knot or surgically remove the catheter from the patient.

<CIT> describes an endoscopic form detection device including a sensor tentative position detecting section configured to detect a tentative position of each sensor unit on the assumption that a portion between the respective sensor units is a linear tentative link whose dimension is equal to an inter-sensor dimension. The endoscopic form detection device includes a sensor position correcting section configured to correct a position of each sensor unit from the tentative position to a final position based on an absolute value of a difference between an arc length of each tentative arc and the inter-sensor dimension, and a final curve form detecting section configured to perform curve interpolation between the final positions of the respective sensor units by using a final arc to detect a final curve form of an inserting section.

<CIT> describes a method comprising measuring, with a sensor, a shape of a section of an elongated flexible instrument and comparing the measured shape of the section of the elongated flexible instrument to an expected shape. The method also comprises determining whether the measured shape of the section of the elongated flexible instrument differs from the expected shape by a predefined threshold.

<CIT> teaches that coiling or looping of a catheter can be recognized from simultaneous recordings of cavity electrograms and intracardiac pressures.

<CIT> describes a device for determining the relative position of two or more catheters in the human body, there being disposed on each catheter, preferably in the area of the catheter tip, at least one measuring electrode which can be connected to a voltage source together with one or more measuring electrodes of a further catheter, wherein the resistance between the measuring electrodes, and hence the distance of the measuring electrodes, can be determined via a current measurement.

A detection system for detecting a loop and/or a knot in a catheter includes a first coil and a second coil in spaced positions on a catheter body of the catheter. A driver is coupled by a wired communication link to the first coil, wherein the driver is configured to transmit a first signal to the first coil. A receiver is coupled by a wired communication link to the second coil, wherein the receiver is configured to receive a second signal from the second coil indicative of a proximity of the first coil and the second coil. A signal analyzer is coupled by a wired or wireless communication link to the receiver that is configured to receive the second signal from the receiver and determine whether there is a change in the second signal indicative of a formation of the loop and/or the knot in the catheter.

A method for detecting a loop and/or a knot in a catheter includes sending a first signal from a driver to a first coil on the catheter and receiving a second signal from a second coil on a catheter in a receiver. The first coil and the second coil are in spaced positions on a catheter body of the catheter, and the second signal is indicative of a proximity of the first coil and the second coil. The second signal is transmitted from the receiver to a signal analyzer that is coupled to the receiver by a wired or wireless communication link. The signal analyzer determines if there is a change in the second signal that indicates the formation of the loop and/or the knot in the catheter.

The invention is defined in the appended claims <NUM>-<NUM>.

<FIG> is a schematic view of pulmonary artery catheter <NUM> in heart H. <FIG> is a top plan view of pulmonary artery catheter <NUM>. Pulmonary artery catheter <NUM> includes catheter body <NUM>, distal port <NUM>, inflatable balloon <NUM>, thermistor <NUM>, thermal filament <NUM>, proximal injectate port <NUM>, volume infusion port <NUM>, first coil <NUM>, second coil <NUM>, third coil <NUM>, catheter body junction <NUM> (shown in <FIG>), extension tubes <NUM> (including extension tubes 124A-<NUM>) (shown in <FIG>), distal port hub <NUM> (shown in <FIG>), balloon inflation valve <NUM> (shown in <FIG>), thermistor connector <NUM> (shown in <FIG>), thermal filament connector <NUM> (shown in <FIG>), proximal injectate lumen hub <NUM> (shown in <FIG>), volume infusion port hub <NUM> (shown in <FIG>), optical module connector <NUM> (shown in <FIG>), and coil connector <NUM> (shown in <FIG>). <FIG> also shows heart H, right atrium RA, right ventricle RV, left atrium LA, left ventricle LV, tricuspid valve TV, pulmonary valve PV, mitral valve MV, aortic valve AV, superior vena cava SVC, inferior vena cava IVC, pulmonary artery PA, pulmonary veins PVS, and aorta AT.

Pulmonary artery catheter <NUM> (also called a Swan-Ganz catheter) can be advanced to a patient's pulmonary artery PA for continuous monitoring of flow, pressure, and oxygen delivery and consumption. When paired with a cardiac output monitor, pulmonary artery catheter <NUM> can provide a comprehensive hemodynamic profile of a patient. A patient's hemodynamic status can be tracked using the comprehensive hemodynamic profile and continuous data to assist physicians in early evaluation of the patient's cardiac status. Specifically, pulmonary artery catheter <NUM> can be used to determine the following parameters when paired with a cardiac monitor: cardiac output (CO), mixed venous oxygen situation (SvO<NUM>), stroke volume (SV), systemic vascular resistance (SVR), right ventricular ejection fraction (RVEF), right ventricular end diastolic volume (RVEDV), right atrial pressure (RAP), pulmonary artery pressure (PAP), pulmonary artery occlusion pressure (PAOP), and diastolic pulmonary artery pressure (PADP).

Pulmonary artery catheter <NUM> includes catheter body <NUM>. Distal port <NUM> is positioned at a distal end of catheter body <NUM>. Distal port <NUM> can be used to monitor the pulmonary artery pressure and allows mixed venous blood samples to be taken from pulmonary artery PA for the assessment of oxygen transport balance and the calculation of oxygen consumption, oxygen utilization coefficient, and intrapulmonary shunt fraction. Inflatable balloon <NUM> is positioned adjacent to distal port <NUM> near the distal end of catheter body <NUM>. Inflatable balloon <NUM> can be inflated when pulmonary artery catheter <NUM> is positioned in heart H and floated into pulmonary artery PA to sense a patient's hemodynamic variables.

Pulmonary artery catheter <NUM> further includes thermistor <NUM> positioned proximal of inflatable balloon <NUM>. Thermistor <NUM> senses a temperature of pulmonary artery PA when inflatable balloon <NUM> is positioned in pulmonary artery PA. The temperature readings are used to calculate cardiac output measurements. Thermal filament <NUM> is positioned proximal of thermistor <NUM>. When inflatable balloon <NUM> is positioned in pulmonary artery PA, thermal filament <NUM> is positioned in right atrium RA and right ventricle RV of heart H. Proximal injectate port <NUM> is positioned proximal of thermal filament <NUM>. When inflatable balloon <NUM> is positioned in pulmonary artery PA, proximal injectate port <NUM> is positioned in right atrium RA of heart H. Proximal injectate port <NUM> can be used to determine a right atrial or central venous pressure, to take blood samples, to infuse medicine to right atrium RA, or to inject a fluid bolus into heart H for cardiac output measurement. Volume infusion port <NUM> is positioned proximal of proximal injectate port <NUM>. When inflatable balloon <NUM> is positioned in pulmonary artery PA of heart H, volume infusion port <NUM> is positioned in right atrium RA of heart H. Volume infusion port <NUM> provides direct access to right atrium RA and allows for continuous infusion into right atrium RA of heart H. In alternate embodiments, pulmonary artery catheter <NUM> can include electrodes for right atrial, right ventricular, or right A-V sequential temporary transvenous pacing.

First coil <NUM>, second coil <NUM>, and third coil <NUM> are positioned on catheter body <NUM> of pulmonary artery catheter <NUM>. In the embodiment shown in <FIG>, first coil <NUM> is positioned between thermistor <NUM> and second coil <NUM>, second coil <NUM> is positioned between first coil <NUM> and thermal filament <NUM>, and third coil <NUM> is positioned between proximal injectate port <NUM> and volume infusion port <NUM>. In alternate embodiments, first coil <NUM>, second coil <NUM>, and third coil <NUM> can be positioned at any location along catheter body <NUM>. Further, in alternate embodiments, pulmonary artery catheter <NUM> can include two coils or four or more coils.

Catheter body junction <NUM> is positioned at a proximal end of catheter body <NUM>. Extending from catheter body junction <NUM> are plurality of extension tubes <NUM>. There are eight extension tubes <NUM> shown in <FIG>, but any number of extension tubes <NUM> can extend from catheter body junction <NUM> in alternate embodiments. Each of extension tubes <NUM> extends from catheter body junction <NUM> to a connector at a proximal end of each extension tube <NUM>.

Distal port hub <NUM> is positioned at a proximal end of extension tube 124A. Distal port hub <NUM> is fluidly connected to distal port <NUM> through a lumen extending through catheter body <NUM> and through extension tube 124A. Balloon inflation valve <NUM> is positioned at a proximal end of extension tube 124B. Balloon inflation valve <NUM> is fluidly connected to inflatable balloon <NUM> through a lumen extending through catheter body <NUM> and through extension tube 124B. An injection device, such as a syringe, can be connected to balloon inflation valve <NUM> to inject a fluid into inflatable balloon <NUM>.

Thermistor connector <NUM> is positioned at a proximal end of extension tube 124C. Thermal filament connector <NUM> is positioned at a proximal end of extension tube 124D. Proximal injectate lumen hub <NUM> is positioned at a proximal end of extension tube 124E. Proximal injectate lumen hub <NUM> is fluidly connected to proximal injectate port <NUM> through a lumen extending through catheter body <NUM> and through extension tube 124E. Volume infusion port hub <NUM> is positioned at a proximal end of extension tube 124F. Volume infusion port hub <NUM> is fluidly connected to volume infusion port <NUM> through a lumen extending through catheter body <NUM> and through extension tube 124F. Optical module connector <NUM> is positioned at a proximal end of extension tube <NUM>.

Coil connector <NUM> is positioned at a proximal end of extension tube <NUM>. Coil connector <NUM> is coupled by a wired communication link to first coil <NUM>, second coil <NUM>, and third coil <NUM>. Coil connector <NUM> is configured to be coupled by a wired communication link to a detection system for detecting loops or knots that may form in catheter body <NUM> of pulmonary artery catheter <NUM>. Coil connector <NUM> thus couples the detection system to first coil <NUM>, second coil <NUM>, and third coil <NUM>.

Pulmonary artery catheter <NUM> can be inserted into a large vein in the patient, typically the internal jugular veins, the subclavian veins, the femoral veins, or the antecubital fossa veins. Pulmonary artery catheter <NUM> is then advanced through the vascular systems and into the right atrium RA of heart H. The passage of pulmonary artery catheter <NUM> to the right atrium RA can be monitored with dynamic pressure readings from distal port <NUM> on pulmonary artery catheter <NUM> and/or with fluoroscopy. Once the distal end of pulmonary artery catheter <NUM> is positioned in right atrium RA of heart H, inflatable balloon <NUM> is inflated. Inflatable balloon <NUM> will then float from right atrium RA, through tricuspid valve TV, into and through right ventricle RV, through pulmonary valve PV, and into pulmonary artery PA. Inflatable balloon <NUM> will float through pulmonary artery PA until it wedges in pulmonary artery PA, as shown in <FIG>.

Pulmonary artery catheter <NUM> can determine hemodynamic parameters as inflatable balloon <NUM> is floated through heart H. Once inflatable balloon <NUM> is wedged in pulmonary artery PA, pulmonary artery catheter <NUM> can determine further hemodynamic parameters. Once the hemodynamic parameters are determined, inflatable balloon <NUM> can be deflated and pulmonary artery catheter <NUM> can be pulled from the patient.

One of the risks associated with advancing pulmonary artery catheter <NUM> into pulmonary artery PA is that pulmonary artery catheter <NUM> can form a loop or knot. Patients with low blood flow are more susceptible to knotting of pulmonary artery catheter <NUM> because pulmonary artery catheter <NUM> is less able to follow the expected trajectory of blood flow through right atrium RA and right ventricle RV into pulmonary artery PA. When pulmonary artery catheter <NUM> does not follow the expected trajectory, it can start coiling and forming one or more loops (most likely in right atrium RA or right ventricle RV of the patient). Eventually, knotting can occur when pulmonary artery catheter <NUM> is pulled. When knotting does occur, a procedure is needed to undo the knot or surgically remove pulmonary artery catheter <NUM> from the patient.

First coil <NUM>, second coil <NUM>, and third coil <NUM> are configured to be coupled to a detection system to detect looping or knotting of catheter body <NUM> of pulmonary artery catheter <NUM>. The detection system is described with respect to <FIG>.

<FIG> is a schematic view of detection system <NUM> for detecting looping and knotting of pulmonary artery catheter <NUM>. <FIG> is a schematic view of detection system <NUM> including coils on pulmonary artery catheter <NUM>. <FIG> will be discussed together. <FIG> show pulmonary artery catheter <NUM> and detection system <NUM>. Catheter <NUM> includes catheter body <NUM> (shown in <FIG>), first coil <NUM> (shown in <FIG>), second coil <NUM> (shown in <FIG>), and third coil <NUM> (shown in <FIG>). Detection system <NUM> includes driver/receiver <NUM>, signal analyzer <NUM>, and display <NUM>. <FIG> also shows patient PT and physician PH. <FIG> also shows first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3.

Catheter <NUM> is schematically shown in <FIG>, but it has the structure and design as shown in and discussed in reference to <FIG>. Catheter <NUM> includes catheter body <NUM> with first coil <NUM>, second coil <NUM>, and third coil <NUM> positioned on catheter body <NUM>. Detection system <NUM> will be discussed here as detecting looping and knotting of catheter <NUM>, but detection system <NUM> can be used with any suitable catheter to prevent looping and knotting of any suitable catheter in alternate embodiments.

Detection system <NUM> is used to detect looping or knotting of catheter body <NUM> of catheter <NUM>. First coil <NUM>, second coil <NUM>, and third coil <NUM> are positioned in spaced positions on catheter body <NUM> and form a part of detection system <NUM>. In the embodiment shown in <FIG> and <FIG>, catheter <NUM> includes three coils, including first coil <NUM>, second coil <NUM>, and third coil <NUM>. In alternate embodiments, detection system <NUM> can include two coils or four or more coils. The more coils that are positioned along catheter body <NUM> can increase the accuracy of detection system <NUM>. In the embodiment shown in <FIG>, first coil <NUM>, second coil <NUM>, and third coil <NUM> are positioned in spaced positions on a distal portion of catheter body <NUM> of catheter <NUM>. The distal portion is the portion of catheter body <NUM> that is positioned in a heart and a pulmonary artery of patient PT when catheter <NUM> is fully positioned in patient PT. First coil <NUM> is positioned between a distal end of catheter <NUM> and second coil <NUM>; second coil <NUM> is positioned between first coil <NUM> and third coil <NUM>; and third coil <NUM> is positioned between second coil <NUM> and a proximal end of catheter <NUM>.

As shown in <FIG>, physician PH can insert catheter <NUM> into patient PT. Catheter <NUM> extends out of patient PT and a proximal end of catheter <NUM> is connected to driver/receiver <NUM> with coil connector <NUM> (shown in <FIG>). First coil <NUM>, second coil <NUM>, and third coil <NUM> are electrically coupled to driver/receiver <NUM> by one or more wired communication links. Driver/receiver <NUM> is configured to send a signal to first coil <NUM>, second coil <NUM>, and/or third coil <NUM> and to receive a signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> in return. Driver/receiver <NUM> is electrically coupled to signal analyzer <NUM> by a wired or wireless communication link. The signal received in driver/receiver <NUM> from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> can be communicated to signal analyzer <NUM> from driver/receiver <NUM>. Signal analyzer <NUM> is configured to analyze the signal.

In the embodiment shown in <FIG>, driver/receiver <NUM> is a single unit. In alternate embodiments, driver/receiver <NUM> can be two separate components. Driver/receiver <NUM> drives first coil <NUM>, second coil <NUM>, and/or third coil <NUM> with an AC signal. Driver/receiver <NUM> can generate an AC current and detect an AC voltage in some embodiments, and driver/receiver <NUM> can generate an AC voltage and detect an AC current in alternate embodiments. When the AC signal is transmitted to first coil <NUM>, second coil <NUM>, and/or third coil <NUM> from driver/receiver <NUM>, a magnetic field is created around each of first coil <NUM>, second coil <NUM>, and/or third coil <NUM>. As shown in <FIG>, first magnetic field MF1 is formed around first coil <NUM>, second magnetic field MF2 is formed around second coil <NUM>, and third magnetic field MF3 is formed around third coil <NUM>. First magnetic field MF1, second magnetic field MF2, and third magnetic field MF3 are schematically shown in <FIG>. The polarity of each of first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3 is shown with arrows in <FIG>. The polarity of each of first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3 are based on the winding and excitation of first coil <NUM>, second coil <NUM>, and third coil <NUM>, respectively, at any given time and the proximity of first coil <NUM>, second coil <NUM>, and third coil <NUM>. A signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> is received in driver/receiver <NUM>. The signal that is received in driver/receiver <NUM> will be indicative of the proximity of first coil <NUM>, second coil <NUM>, and third coil <NUM> to one another. When catheter <NUM> is not looped or knotted, the signal that is received in driver/receiver <NUM> will correlate to first coil <NUM>, second coil <NUM>, and third coil <NUM> being in spaced positions on the distal portion of catheter body <NUM> of catheter <NUM>. If a loop or knot starts to form in catheter body <NUM> of catheter <NUM>, the signal that is received in driver/receiver <NUM> will indicate a change that is indicative of first coil <NUM>, second coil <NUM>, and third coil <NUM> coming into proximity with one another and the formation of the loop and/or the knot in catheter body <NUM> of catheter <NUM>. To simplify the description herewith, the mutual coupling (inductance) of first coil <NUM>, second coil <NUM>, and/or third coil <NUM> will be ignored hereinafter.

Detection system <NUM> is configured to detect changes in first magnetic field MF1, second magnetic field MF2, and/or third magnetic field MF3 when a loop or a knot starts to form in catheter <NUM>. Driver/receiver <NUM> is configured to receive a signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> that is indicative of the proximity of first coil <NUM>, second coil <NUM>, and third coil <NUM> to one another. The signal received in driver/receiver <NUM> is then transmitted to signal analyzer <NUM> and can be analyzed by signal analyzer <NUM>.

In a first embodiment, driver/receiver <NUM> can be coupled to one or more of first coil <NUM>, second coil <NUM>, and third coil <NUM> along a first wired communication link and to the remaining of first coil <NUM>, second coil <NUM>, and third coil <NUM> along a second wired communication link. In this embodiment, driver/receiver <NUM> will drive the one or more coils (transmit coil(s)) connected to the first wired communication link and receive a signal from the one or more coils (receive coil(s)) connected to the second wired communication link. When the driver/receiver <NUM> drives the transmit coil(s) connected to the first wired communication link with an AC signal, a magnetic field if created around each of the transmit coil(s). A signal is induced into the receive coil(s) due to the proximity of the coils that is indicative of the proximity of first coil <NUM>, second coil <NUM>, and third coil <NUM> to one another. If a loop or knot starts to form in catheter body <NUM> of catheter <NUM>, the signal that is received in driver/receiver <NUM> will indicate a change that is indicative of first coil <NUM>, second coil <NUM>, and third coil <NUM> coming into proximity with one another and the formation of the loop and/or the knot in catheter body <NUM> of catheter <NUM>.

In a second embodiment, driver/receiver <NUM> can be coupled to first coil <NUM>, second coil <NUM>, and third coil <NUM> along a single wired communication link. First coil <NUM>, second coil <NUM>, and third coil <NUM> can be coupled in series or in parallel to the wired communication link. In this embodiment, driver/receiver <NUM> will drive first coil <NUM>, second coil <NUM>, and third coil <NUM> and receive a signal from first coil <NUM>, second coil <NUM>, and third coil <NUM>. The signal that is received in driver/receiver <NUM> will be a function of an impedance of first coil <NUM>, second coil <NUM>, and third coil <NUM>, and the coupling thereof, that is indicative of the proximity of first coil <NUM>, second coil <NUM>, and third coil <NUM> to one another. If a loop or knot starts to form in catheter body <NUM> of catheter <NUM>, the signal that is received in driver/receiver <NUM> will indicate a change in impedance that is indicative of first coil <NUM>, second coil <NUM>, and third coil <NUM> coming into proximity with one another and the formation of the loop and/or the knot in catheter body <NUM> of catheter <NUM>.

Changes in the signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> can include changes to the amplitude (or magnitude), polarity (or phase), and/or trend of the signal that indicates changes to first magnetic field MF1, second magnetic field MF2, and/or third magnetic field MF3. Signal analyzer <NUM> uses an algorithm to compute the likelihood of loop or knot formation based on an analysis of the amplitude, polarity, and/or trend of the signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM>.

Signal analyzer <NUM> is electrically coupled to display <NUM> by a wired or wireless communication link. After the signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> is analyzed by signal analyzer <NUM>, an instruction signal is transmitted from signal analyzer <NUM> to display <NUM>. Display <NUM> can be configured to display a representation of the signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM>, provide an alarm to physician PH regarding looping and/or knotting of catheter <NUM>, and/or instruct physician PH regarding the advancement or removal of catheter <NUM> when looping and/or knotting of catheter <NUM> has occurred. For example, the instruction signal that is communicated to display <NUM> can include an instruction to display an amplitude and a polarity of the signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> on display <NUM>. If signal analyzer <NUM> has detected a change in the signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> that indicates the formation of a loop and/or a knot in catheter <NUM>, the instruction signal can include an instruction to display <NUM> to provide an alarm to physician PH. Further, if signal analyzer <NUM> has detected a change in the signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> that indicates the formation of a loop and/or a knot in catheter <NUM>, the instruction signal can include instructions that are to be provided to physician PH through display <NUM> regarding the advancement or removal of catheter <NUM>.

Detection system <NUM> provides a method for real-time, continuous, uninterrupted detection of catheter loop formation and issuance of an alarm if a knot is likely to form. Detection system <NUM> is suitable for guiding the floating procedure of pulmonary artery catheter <NUM> to prevent knotting of pulmonary artery catheter <NUM>. Detection system <NUM> can determine whether a loop or knot is forming in pulmonary artery catheter <NUM> based on an analysis of signals from first coil <NUM>, second coil <NUM>, and/or third coil <NUM>. Compared to prior art devices, no extra-corporeal sensing devices are required. Further, detection system <NUM> provides higher immunity to metal bodies that are close to patient PT that can affect first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3 of first coil <NUM>, second coil <NUM>, and third coil <NUM>, respectively, as an extra-corporeal sensing device is not needed. This allows catheter <NUM> and detection system <NUM> to be used in clinic or hospital settings around medical equipment utilizing magnetic fields.

<FIG> is a schematic view of a first configuration of detection system <NUM>. <FIG> shows first coil <NUM>, second coil <NUM>, third coil <NUM>, and detection system <NUM>, which includes driver/receiver <NUM> (including driver 152A and receiver 152B), signal analyzer <NUM>, display <NUM>, transmit wires <NUM>, and receive wires <NUM>. <FIG> also shows first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3.

Catheter <NUM> and catheter body <NUM> are not shown in <FIG> for clarity. <FIG> above show the structure and design of catheter <NUM> and catheter body <NUM>, including the positioning of first coil <NUM>, second coil <NUM>, and third coil <NUM> in spaced positions on the distal portion of catheter body <NUM>. Detection system <NUM> will be discussed here as detecting looping and knotting of catheter <NUM>, but detection system <NUM> can be used with any suitable catheter to prevent looping and knotting of any suitable catheter in alternate embodiments. Detection system <NUM> is used to detect looping or knotting of catheter body <NUM> of catheter <NUM>. First coil <NUM>, second coil <NUM>, and third coil <NUM> are positioned in spaced positions on catheter body <NUM> and form a part of detection system <NUM>.

Detection system <NUM> has generally the same structure and design as discussed above with respect to <FIG>, however driver/receiver <NUM> includes driver 152A and receiver 152B that are separate components in the configuration of detection system <NUM> shown in <FIG>. In the configuration of detection system <NUM> shown in <FIG>, second coil <NUM> and third coil <NUM> are electrically coupled to driver 152A with transmit wires <NUM>, and first coil <NUM> is electrically coupled to receiver 152B with receive wires <NUM>. Second coil <NUM> and third coil <NUM> are shown as being connected in series in the embodiment shown in <FIG>, but can also be connected in parallel along transmit wires <NUM>. Driver 152A is configured to send a signal to second coil <NUM> and third coil <NUM>, and receiver 152B is configured to receive a signal from first coil <NUM>. As such, second coil <NUM> and third coil <NUM> are transmit coils and first coil <NUM> is a receive coil. In alternate embodiments, detection system <NUM> can include one transmit coil and one receive coil, two or more transmit coils and one receive coil, one transmit coil and two or more receive coils, or two or more transmit coils and two or more receive coils. If two or more receive coils are included, the receive coils can be connected in series or in parallel along receive wires <NUM>. Receiver 152B is electrically coupled to signal analyzer <NUM> by a wired or wireless communication link. The signal received in receiver 152B from first coil <NUM> can be communicated to signal analyzer <NUM> from receiver 152B. Signal analyzer <NUM> is configured to analyze the signal.

Driver 152A drives second coil <NUM> and third coil <NUM> (the transmit coils) with an AC signal. Driver 152A can generate an AC current or an AC voltage. When driven with the AC signal, a magnetic field is created around each of second coil <NUM> and third coil <NUM>. As shown in <FIG>, second magnetic field MF2 is formed around second coil <NUM> and third magnetic field MF3 is formed around third coil <NUM>. The polarity of each of second magnetic field MF2 and third magnetic field MF3 is shown with arrows in <FIG>. The polarity of each of second magnetic field MF2 and third magnetic field MF3 are based on the winding and excitation of second coil <NUM> and third coil <NUM>, respectively, at any given time and the proximity of second coil <NUM> and third coil <NUM>.

A signal is induced into first coil <NUM> (the receive coil) due to the proximity of first coil <NUM> to second coil <NUM> and third coil <NUM>. Magnetic field MF1 is formed around first coil <NUM>. A signal from first coil <NUM> (the receive coil) is received in receiver 152B. Receiver 152B can detect an AC voltage or an AC current. The signal that is received in receiver 152B will be indicative of the proximity of first coil <NUM>, second coil <NUM>, and/or third coil <NUM> to one another. When catheter <NUM> is not looped or knotted, the signal that is received in receiver 152B will correlate to first coil <NUM>, second coil <NUM>, and third coil <NUM> being in spaced positions on the distal portion of catheter body <NUM> of catheter <NUM>. If a loop or knot starts to form in catheter body <NUM> of catheter <NUM>, the signal that is received in receiver 152B will indicate a change that is indicative of first coil <NUM>, second coil <NUM>, and/or third coil <NUM> coming into proximity with one another and the formation of the loop and/or the knot in catheter body <NUM> of catheter <NUM>. Due to the transmit and receive reciprocity, first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3 are also indicative of their spatial sensitivity to externally generated fields.

Detection system <NUM> is configured to detect changes in first magnetic field MF1 of first coil <NUM> (the receive coil) when a loop or a knot starts to form in catheter <NUM>. Receiver 152B is configured to receive a signal from first coil <NUM> that is indicative of the proximity of first coil <NUM>, second coil <NUM>, and third coil <NUM> to one another. The signal received in receiver 152B is then sent to signal analyzer <NUM> and can be analyzed by signal analyzer <NUM>. Changes in the signal from first coil <NUM> (the receive coil) can include changes to the amplitude, polarity, and/or trend of the signal that indicates changes to first magnetic field MF1 of first coil <NUM>. Signal analyzer <NUM> uses an algorithm to compute the likelihood of loop or knot formation based on an analysis of the amplitude, polarity, and/or trend of the signal from first coil <NUM>.

Signal analyzer <NUM> is electrically coupled to display <NUM> by a wired or wireless communication link. After the signal from first coil <NUM> is analyzed by signal analyzer <NUM>, an instruction signal is communicated from signal analyzer <NUM> to display <NUM>. Display <NUM> can be configured to display a representation of the signal from first coil <NUM>, provide an alarm to physician PH regarding looping and/or knotting of catheter <NUM>, and/or instruct physician PH regarding the advancement or removal of catheter <NUM> when looping and/or knotting of catheter <NUM> has occurred. For example, the instruction signal that is communicated to display <NUM> can include an instruction to display an amplitude and a polarity of the signal from first coil <NUM> on display <NUM>. If signal analyzer <NUM> has detected a change in the signal from first coil <NUM> that indicates the formation of a loop and/or a knot in catheter <NUM>, the instruction signal can include an instruction to display <NUM> to provide an alarm to physician PH. Further, if signal analyzer <NUM> has detected a change in the signal from first coil <NUM> that indicates the formation of a loop and/or a knot in catheter <NUM>, the instruction signal can include instructions that are to be provided to physician PH through display <NUM> regarding the advancement or removal of catheter <NUM>.

Having one or more of first coil <NUM>, second coil <NUM>, and third coil <NUM> be a transmit coil(s) and one or more of first coil <NUM>, second coil <NUM>, and third coil <NUM> be a receive coil(s) permits for use of receiver 152B with a lower dynamic range and/or reduces the direct electrical noise coupling between driver 152A and receiver 152B. This allows a lower current or voltage level to be used to drive first coil <NUM>, second coil <NUM>, and/or third coil <NUM>.

<FIG> is a schematic view of pulmonary artery catheter <NUM> and detection system <NUM> with lock-in amplifier <NUM>. Pulmonary artery catheter <NUM> includes catheter body <NUM>, first coil <NUM>, second coil <NUM>, and third coil <NUM>. Detection system <NUM> includes driver/receiver <NUM>, signal analyzer <NUM>, display <NUM>, lock-in amplifier <NUM>, transmit wire <NUM>, capacitor <NUM>, receive wire <NUM>, capacitor <NUM>, and ground <NUM>. Lock-in amplifier <NUM> includes reference source <NUM>, demodulator <NUM>, and low pass filter <NUM>. <FIG> also shows first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3.

Catheter <NUM>, catheter body <NUM>, first coil <NUM>, second coil <NUM>, and third coil <NUM> are schematically shown in <FIG>, but have the structure and design as shown in and discussed in reference to <FIG>. Detection system <NUM> will be discussed here as detecting looping and knotting of catheter <NUM>, but detection system <NUM> can be used with any suitable catheter to prevent looping and knotting of any suitable catheter in alternate embodiments.

Detection system <NUM> includes driver/receiver <NUM>, signal analyzer <NUM> and display <NUM>, as discussed above in reference to <FIG>. Driver/receiver <NUM> includes lock-in amplifier <NUM> in the embodiment shown in <FIG>. Lock-in amplifier <NUM> is one version of driver/receiver <NUM> that can be used in detection system <NUM>. Lock-in amplifier <NUM> is configured to send a signal to and receive a signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM>. Lock-in amplifier <NUM> is one example of driver/receiver <NUM> that can be used to drive first coil <NUM>, second coil <NUM>, and/or third coil <NUM> and receive signals from first coil <NUM>, second coil <NUM>, and/or third coil <NUM>. In alternate embodiments, any suitable mechanism can be used for driver/receiver <NUM>.

In the embodiment shown in <FIG>, lock-in amplifier <NUM> is a multi-channel lock-in amplifier, second coil <NUM> and third coil <NUM> are transmit coils, and first coil <NUM> is a receive coil. Lock-in amplifier <NUM> sends the signal to second coil <NUM> and third coil <NUM> along transmit wire <NUM> that is electrically coupled to second coil <NUM> and third coil <NUM>. Transmit wire <NUM> is shown as being a single wire in the embodiment shown in <FIG>, but can include a second (return or ground) wire that is not shown for simplicity. Lock-in amplifier <NUM> sends a sinusoidal signal (AC signal) to second coil <NUM> and third coil <NUM> that is preferably between <NUM> Hertz (Hz) and <NUM> kiloHertz (kHz). Capacitor <NUM> is positioned along transmit wire <NUM> between lock-in amplifier <NUM> and third coil <NUM>. Capacitor <NUM> acts as a short circuit for high frequencies and will block DC components. Capacitor <NUM> is tuned to create series resonance with second coil <NUM> and third coil <NUM> to maximize current passing through second coil <NUM> and third coil <NUM>. The sinusoidal signal drives second coil <NUM> and third coil <NUM>.

Receive wire <NUM> will extend from and electrically couple first coil 116to lock-in amplifier <NUM>. Receive wire <NUM> is shown as being a single wire in the embodiment shown in <FIG>, but can include a second (return or ground) wire that is not shown for simplicity. A signal from first coil 116will be received in lock-in amplifier <NUM> along receive wire <NUM>. Capacitor <NUM> and ground <NUM> are positioned along receive wire <NUM> between first coil <NUM> and lock-in amplifier <NUM>. Capacitor <NUM> and ground <NUM> will remove highfrequency signals from the signal being received from first coil <NUM>. Capacitor <NUM> is tuned to create parallel resonance to maximize voltage detected at a frequency of interest.

Lock-in amplifier <NUM> includes reference source <NUM>, demodulator <NUM>, and low pass filter <NUM>. Reference source <NUM> generates the sinusoidal signal (AC signal) that is sent to second coil <NUM> and third coil <NUM> along transmit wire <NUM>. Reference source <NUM> also sends the sinusoidal signal (AC signal) to demodulator <NUM> of lock-in amplifier <NUM> to act as a reference signal for demodulator <NUM>. Demodulator <NUM> receives the signal from first coil 116along receive wire <NUM>. Demodulator <NUM> uses the reference signal from reference source <NUM> to demodulate the signal received from first coil <NUM>. Demodulator <NUM> then sends the signal to low pass filter <NUM>, which filters out AC artifacts. The resulting signal is correlated to the proximity of first coil <NUM>, second coil <NUM>, and third coil <NUM> to one another.

The resulting signal in lock-in amplifier <NUM> is then communicated from lock-in amplifier <NUM> to signal analyzer <NUM>. As discussed above in reference to <FIG>, signal analyzer <NUM> analyzes the signal from lock-in amplifier <NUM> to determine whether there is a change to the amplitude, polarity, or trend of the signal that indicates the formation of a loop and/or a knot in catheter <NUM>. If there is a change indicating the formation of a loop and/or a knot in catheter <NUM>, signal analyzer <NUM> can provide an instruction signal to display <NUM> to display the signal, provide an alarm, and instruct a physician on the advancement or removal of catheter <NUM>.

<FIG> is a schematic view of coils on pulmonary artery catheter <NUM> when pulmonary artery catheter <NUM> is not looped or knotted. <FIG> is a graph showing an amplitude and polarity of signal S1 from the coils when pulmonary artery catheter <NUM> is not looped or knotted. <FIG> is a schematic view of the coils on pulmonary artery catheter <NUM> when pulmonary artery catheter <NUM> starts to loop. <FIG> is a graph showing an amplitude and polarity of signal S2 when pulmonary artery catheter <NUM> starts to loop. <FIG> is a schematic view of the coils on pulmonary artery catheter <NUM> when pulmonary artery catheter <NUM> has formed a loop. <FIG> is a graph showing an amplitude and polarity of signal S3 when pulmonary artery catheter <NUM> has formed a loop. <FIG>, <FIG> show catheter <NUM> (including catheter body <NUM>, first coil <NUM>, and second coil <NUM>), first magnetic field MF1, and second magnetic field MF2. <FIG> shows signal S1. <FIG> shows signal S2. <FIG> shows signal S3.

Catheter <NUM> has the structure and design as described above in reference to <FIG>. Catheter <NUM> is connected to detection system <NUM> as described above in reference to <FIG>. Third coil <NUM> and third magnetic field MF3 have been omitted for clarity in <FIG>, <FIG>. In <FIG>, driver/receiver <NUM> (shown in <FIG>) sends a signal to and receives a signal from first coil <NUM> and/or second coil <NUM>. First coil <NUM> has first magnetic field MF1, and second coil <NUM> has second magnetic field MF2. First coil <NUM> and second coil <NUM> are instrumented such that their amplitude and polarity are known when catheter <NUM> is not looped or knotted, as shown with the arrows in <FIG>. In the embodiment shown in <FIG>, first coil <NUM> and second coil <NUM> have aligned polarities.

<FIG> shows catheter <NUM> with no loops or knots as it is advanced into the patient. As shown in <FIG>, first magnetic field MF1 and second magnetic field MF2 of first coil <NUM> and second coil <NUM>, respectively, have aligned polarity. Second coil <NUM> generates second magnetic field MF2 and first coil <NUM> generates second magnetic field MF1. <FIG> shows a graph showing an amplitude and polarity of signal S1 when catheter <NUM> is not looped or knotted. Signal S1 is a signal received from first coil <NUM> and/or second coil <NUM>. As shown in <FIG>, signal S1 has a small amplitude and positive polarity.

<FIG> shows catheter <NUM> as it starts to loop. A distal end of catheter <NUM> has turned backwards so first coil <NUM> has a reversed orientation and is positioned adjacent to second coil <NUM>. As shown in <FIG>, the polarity of first magnetic field MF1 of first coil <NUM> has switched due to the proximity of first coil <NUM> and second coil <NUM>. <FIG> shows a graph showing an amplitude and polarity of signal S2 when catheter <NUM> has started to loop. Signal S2 is a signal received from first coil <NUM> and/or second coil <NUM>. As shown in <FIG>, signal S2 has a large amplitude and negative polarity.

<FIG> shows catheter <NUM> when a loop has formed. A distal portion of catheter <NUM> has looped so that first coil <NUM> has regained its original orientation and is positioned adjacent to second coil <NUM>. As shown in <FIG>, the polarity of first magnetic field MF1 and second magnetic field MF2 of first coil <NUM> and second coil <NUM>, respectively, are realigned because first coil <NUM> has regained its original orientation. <FIG> shows a graph showing an amplitude and polarity of signal S3 when catheter <NUM> has formed a loop. Signal S3 is a signal received from first coil <NUM> and/or second coil <NUM>. As shown in <FIG>, signal S3 has a large amplitude and positive polarity.

When first coil <NUM> and second coil <NUM> are positioned apart, as shown in <FIG>, signal S1 has a smaller amplitude. When first coil <NUM> and second coil <NUM> get closer together, as shown in <FIG>, the signal will get stronger due to the proximity of first coil <NUM> and second coil <NUM> and the amplitude of the signal will get bigger. This can be seen in signal S2 shown in <FIG> and signal S3 shown in <FIG>. When the loop starts to form and the orientation of first coil <NUM> is reversed, as shown in <FIG>, signal S2 will be negative due to the differences in polarity of first magnetic field MF1 of first coil <NUM> and second magnetic field MF2 of second coil <NUM>. When a loop is complete and first coil <NUM> is reoriented, as shown in <FIG>, signal S3 will be positive because the polarity of first magnetic field MF1 and second magnetic field MF2 of first coil <NUM> and second coil <NUM>, respectively, are again aligned.

<FIG> is a graph showing an amplitude of signal S4 as pulmonary artery catheter <NUM> is advanced from right atrium RA to pulmonary artery PA. <FIG> is a graph showing an amplitude of signal S5 as pulmonary artery catheter <NUM> forms a loop in right atrium RA. <FIG> show region RAR, region RVR, region PAR, dashed line TV1, and dashed line PV1. <FIG> also shows signal S4. <FIG> also shows signal S5.

<FIG> shows changes to signal S4 as catheter <NUM> (shown in <FIG>) is advanced from right atrium RA (shown in <FIG>) to pulmonary artery PA (shown in <FIG>). Signal S4 is a signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> (shown in <FIG>) on catheter <NUM>. <FIG> shows region RAR, which is when catheter <NUM> is in right atrium RA, region RVR, which is when catheter <NUM> is in right ventricle RV (shown in <FIG>), and region PAR, which is when catheter <NUM> is in pulmonary artery PA. <FIG> shows dashed line TV1, which represents the point at which catheter <NUM> passes from right atrium RA through tricuspid valve TV (shown in <FIG>) into right ventricle RV, and dashed line PV1, which is the point at which catheter <NUM> passes from right ventricle RV through pulmonary valve PV (shown in <FIG>) into pulmonary artery PA.

Signal S4 has a small, positive amplitude as catheter <NUM> is advanced through right atrium RA, shown in the graph of <FIG> in region RAR. Catheter <NUM> passes from right atrium RA to right ventricle RV through tricuspid valve TV, shown in the graph of <FIG> as dashed line TV1. Signal S4 moves from having a small, positive amplitude to having a small, negative amplitude as catheter <NUM> passes through tricuspid valve TV. After catheter <NUM> passes through tricuspid valve TV, signal S4 has a small, negative amplitude as catheter <NUM> is advanced through right ventricle RV, shown in the graph of <FIG> in region RVR. Catheter <NUM> has to turn in right ventricle RV due to the anatomy of right ventricle RV, which will position first coil <NUM> adjacent to and in a different orientation from second coil <NUM>, causing the negative amplitude. As catheter <NUM> approaches pulmonary valve PV, the amplitude of signal S4 will become positive as first coil <NUM> advances away from second coil <NUM> and as second coil <NUM> turns in right ventricle RV. Catheter <NUM> passes from right ventricle RV to pulmonary artery PA through pulmonary valve PV, shown in the graph of <FIG> as dashed line PV1. Signal S4 has a small, positive amplitude as catheter <NUM> is advanced through and wedged in pulmonary artery PA, shown in the graph of <FIG> as region PAR.

<FIG> shows changes to signal S5 as catheter <NUM> is looped in right atrium RA. Signal S5 is a signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> (shown in <FIG>) on catheter <NUM>. <FIG> includes region RAR, region RVR, region PAR, dashed line TV1, and dashed line PV1, as discussed above in reference to <FIG>. As shown in <FIG>, signal S5 begins with a small, positive amplitude before the amplitude increases slightly as catheter <NUM> begins to loop. Signal S5 then experiences a large, negative amplitude as catheter <NUM> begins to form a loop and first coil <NUM> reorients and gets closer to second coil <NUM>. As catheter <NUM> loops further, first coil <NUM> will reorient but remain close to second coil <NUM>, which causes signal S5 to experience a large, positive amplitude. As catheter <NUM> completes the loop, first coil <NUM> will move away from second coil <NUM>, which causes the amplitude of signal S5 to decrease.

The amplitude, polarity, and/or trend of the signals from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> are informative as to the trajectory of pulmonary artery catheter <NUM>. A large amplitude can indicate the likely formation of a loop and/or a knot. Further, an increase in an amplitude and a change in polarity can indicate the likely formation of a loop and/or a knot.

The graphs shown in <FIG> are examples of graphs of signals that can be displayed on display <NUM> of detection system <NUM> (shown in <FIG>).

<FIG> is a block diagram of detection system <NUM> for detecting looping and knotting of pulmonary artery catheter <NUM>. <FIG> shows pulmonary artery catheter <NUM> and detection system <NUM>. Pulmonary artery catheter <NUM> includes catheter body <NUM>, distal port <NUM>, first coil <NUM>, second coil <NUM>, and third coil <NUM>. Detection system <NUM> includes coil driver/receiver <NUM>, pressure sensor receiver <NUM>, signal analyzer <NUM>, and display <NUM>. <FIG> also shows first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3.

Catheter <NUM> is schematically shown in <FIG>, but it has the structure and design as shown in and discussed in reference to <FIG>. Catheter <NUM> includes catheter body <NUM> with distal port <NUM>, first coil <NUM>, second coil <NUM>, and third coil <NUM> positioned on catheter body <NUM>. Detection system <NUM> will be discussed here as detecting looping and knotting of catheter <NUM>, but detection system <NUM> can be used with any suitable catheter to prevent looping and knotting of any suitable catheter in alternate embodiments.

Detection system <NUM> is used to detect looping and knotting of catheter body <NUM> of catheter <NUM>. Detection system <NUM> has components similar to detection system <NUM> discussed above in reference to <FIG>, including first coil <NUM>, second coil <NUM>, third coil <NUM>, coil driver/receiver <NUM>, signal analyzer <NUM>, and display <NUM>. However, detection system <NUM> further includes pressure sensor receiver <NUM>.

In the embodiment shown in <FIG>, coil driver/receiver <NUM> has the same structure and design of driver/receiver <NUM> of detection system <NUM> discussed above in reference to <FIG>. Coil driver/receiver <NUM> is connected to catheter <NUM> with coil connector <NUM> (shown in <FIG>). First coil <NUM>, second coil <NUM>, and third coil <NUM> are electrically coupled to coil driver/receiver <NUM> by a wired communication link. Coil driver/receiver <NUM> is configured to send a signal to and receive a signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM>. Coil driver/receiver <NUM> can include a lock-in amplifier, as discussed in reference to <FIG>, or can be any other suitable driver/receiver. Coil driver/receiver <NUM> is electrically coupled to signal analyzer <NUM> by a wired or wireless communication link. The coil signal received in coil driver/receiver <NUM> from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> can be communicated to signal analyzer <NUM> from coil driver/receiver <NUM>.

Driver/receiver <NUM> drives first coil <NUM>, second coil <NUM>, and/or third coil <NUM>. A magnetic field is created around each of first coil <NUM>, second coil <NUM>, and third coil <NUM>. As shown in <FIG>, first magnetic field MF1 is formed around first coil <NUM>, second magnetic field MF2 is formed around second coil <NUM>, and third magnetic field MF3 is formed around third coil <NUM>. First magnetic field MF1, second magnetic field MF2, and third magnetic field MF3 are schematically shown in <FIG>. The polarity of each of first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3 is shown by arrows in <FIG>.

Detection system <NUM> also includes pressure sensor receiver <NUM>. Pressure sensor receiver <NUM> is configured to receive a mixed venous blood sample from distal port <NUM> and determine a pressure at a distal end of catheter <NUM> and/or receive a signal from a pressure sensor positioned at a distal end of catheter <NUM> representative of a pressure at the distal end of catheter <NUM>. Pressure sensor receiver <NUM> is electrically coupled to signal analyzer <NUM> by a wired or wireless communication link. Pressure sensor receiver <NUM> is configured to transmit a pressure signal determined by or received by pressure sensor receiver <NUM> to signal analyzer <NUM>.

In the embodiment shown in <FIG>, pressure sensor receiver <NUM> is connected to catheter <NUM> using distal port hub <NUM> (shown in <FIG>). Distal port <NUM> is positioned at a distal end of catheter body <NUM> and is configured to take a mixed venous blood sample at the distal end of catheter body <NUM>. Distal port hub <NUM> is fluidly connected to distal port <NUM> through a lumen extending through catheter body <NUM> and through extension tube 124A. Pressure sensor receiver <NUM> is configured to receive the mixed venous blood sample from distal port <NUM> and to determine a pressure at the distal end of catheter body <NUM> using the mixed venous blood sample. Pressure sensor receiver <NUM> can include a pressure sensor or any other suitable electronics that are configured to determine a pressure based on the sample received from distal port <NUM>. In some embodiments, pressure sensor receiver <NUM> can also include components to determine additional parameters from the mixed venous blood sample taken from distal port <NUM>, such as the assessment of oxygen transport balance and the calculation of oxygen consumption, oxygen utilization coefficient, and intrapulmonary shunt fraction. In an alternate embodiment, catheter <NUM> can include a pressure sensor positioned at a distal end of catheter <NUM> that determines a pressure at the distal end of catheter <NUM> and sends a pressure signal representative of the pressure to pressure sensor receiver <NUM>.

Signal analyzer <NUM> is configured to analyze both the coil signal from coil driver/receiver <NUM> and the pressure signal from pressure sensor receiver <NUM>. Signal analyzer <NUM> is configured to detect changes in first magnetic field MF1, second magnetic field MF2, and/or third magnetic field MF3 from the coil signal and changes in pressure at a distal end of catheter <NUM> from the pressure signal. Changes occur in first magnetic field MF1, second magnetic field MF2, and/or third magnetic field MF3 and changes occur in an expected pressure at a distal end of catheter <NUM> when a loop and/or a knot starts to form in catheter <NUM>. Changes in first magnetic field MF1, second magnetic field MF2, and/or third magnetic field MF3 and changes in an expected pressure at the distal end of catheter <NUM> can be analyzed by signal analyzer <NUM>. Signal analyzer <NUM> uses an algorithm to compute the likelihood of loop and/or knot formation based on an analysis of the amplitude, polarity, and/or trend of the changes of first magnetic field MF1, second magnetic field MF2, and third magnetic field MF3 of first coil <NUM>, second coil <NUM>, and third coil <NUM> and the pressure at a distal end of catheter <NUM>.

The expected signals and changes in the expected signals from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> when a loop or a knot forms are discussed above in reference to <FIG>. Additionally, there are expected pressures at a distal end of catheter <NUM> based on where the distal end of catheter <NUM> is in a patient's heart (i.e., when it is floating through the right atrium, the right ventricle, and the pulmonary artery, and when it wedges in the pulmonary artery). Changes in the pressure compared to the expected pressure can be determined by signal analyzer <NUM> and may indicate the formation of a loop and/or a knot in catheter <NUM>.

Signal analyzer <NUM> is electrically coupled to display <NUM> by a wired or wireless communication link. After the coil signal and the pressure signal are analyzed by signal analyzer <NUM>, an instruction signal is communicated from signal analyzer <NUM> to display <NUM>. Display <NUM> can be configured to display a representation of the coil signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> and the pressure signal from pressure sensor receiver <NUM>, provide an alarm to physician PH regarding looping and/or knotting of catheter <NUM>, and/or instruct physician PH regarding the advancement or removal of catheter <NUM> when looping and/or knotting of catheter <NUM> has occurred. For example, the instruction signal that is communicated to display <NUM> can include an instruction to display an amplitude and a polarity of the coil signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> and a pressure at the distal end of catheter <NUM> from the pressure signal on display <NUM>. If signal analyzer <NUM> has detected a change in the coil signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> and/or a change in the pressure signal that indicates the formation of a loop and/or a knot in catheter <NUM>, the instruction signal can include an instruction to display <NUM> to provide an alarm to physician PH. Further, if signal analyzer <NUM> has detected a change in the coil signal from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> and/or a change in the pressure signal that indicates the formation of a loop and/or a knot in catheter <NUM>, the instruction signal can include instructions that are to be provided to physician PH through display <NUM> regarding the advancement or removal of catheter <NUM>.

Detection system <NUM> provides a method for real-time, continuous, uninterrupted detection of catheter loop formation and issuance of an alarm if a knot is likely to form. Detection system <NUM> can determine whether a loop or knot is forming in catheter <NUM> based on an analysis of coil signals from first coil <NUM>, second coil <NUM>, and/or third coil <NUM> and pressure signals from catheter <NUM>.

<FIG> is a side view of coil <NUM> on pulmonary artery catheter <NUM>. Pulmonary artery catheter <NUM> includes catheter body <NUM>, first wire <NUM>, second wire <NUM>, coil <NUM> (including wire <NUM>), first aperture <NUM>, second aperture <NUM>, soldering <NUM>, soldering <NUM>, and protective sheath <NUM>.

Catheter <NUM> includes catheter body <NUM>. First wire <NUM> and second wire <NUM> extend through a lumen in catheter body <NUM> of catheter <NUM>. Coil <NUM> is positioned on a distal portion of catheter body <NUM>. Coil <NUM> can be any of first coil <NUM>, second coil <NUM>, or third coil <NUM> shown in and discussed in reference to <FIG> and <FIG>, or any other suitable coil. Coil <NUM> includes wire <NUM> that is wound around catheter body <NUM> of catheter <NUM>. In an alternate embodiment, catheter body <NUM> of catheter <NUM> can have a recess for coil <NUM> to sit in.

Catheter body <NUM> includes first aperture <NUM> and second aperture <NUM> extending through catheter body <NUM>. Wire <NUM> is wound around catheter body <NUM> extending from first aperture <NUM> to second aperture <NUM>. In the embodiment shown in <FIG>, wire <NUM> is connected to first wire <NUM> at first aperture <NUM> and second wire <NUM> at second aperture <NUM>. In alternate embodiments of catheter body <NUM> including additional coils, wire <NUM> can be connected to first wire <NUM> at first aperture <NUM> and second aperture <NUM>, and a second coil can be connected to first wire <NUM> and second wire <NUM>. Wire <NUM> is soldered to first wire <NUM> at first aperture <NUM> with soldering <NUM> and to second wire <NUM> at second aperture <NUM> with soldering <NUM>. Protective sheath <NUM> is positioned over wire <NUM>, soldering <NUM>, and soldering <NUM> and acts as an electrical insulator. Protective sheath <NUM> is shown as being transparent in <FIG> for clarity. Protective sheath <NUM> can be a heat-shrinkable sheath. Coil <NUM> can be integrated into catheter <NUM> using an automated extrusion process.

<FIG> is a side view of first wire pattern <NUM> for a coil. <FIG> is a side view of second wire pattern <NUM> for a coil. <FIG> will be discussed together. First wire pattern <NUM> includes first wire <NUM> and second wire <NUM>. Second wire pattern <NUM> includes first wire <NUM> and second wire <NUM>.

<FIG> shows first wire pattern <NUM> that includes first wire <NUM> and second wire <NUM> that are together twisted around the catheter body of the catheter. First wire <NUM> and second wire <NUM> are coupled together. First wire pattern <NUM> has a small period between first wire <NUM> and second wire <NUM>. First wire pattern <NUM> is configured to reduce interference between first wire <NUM>, second wire <NUM>, and their surroundings.

<FIG> shows second wire pattern <NUM> that includes first wire <NUM> and second wire <NUM> that are together twisted around the catheter body of the catheter. First wire <NUM> and second wire <NUM> are coupled together. Second wire pattern <NUM> has a larger period between first wire <NUM> and second wire <NUM>. Second wire pattern <NUM> is configured to reduce interference between first wire <NUM>, second wire <NUM>, and their surroundings.

Claim 1:
A detection system (<NUM>) for detecting a loop and/or a knot in a catheter (<NUM>), the detection system (<NUM>) comprising:
a first coil (<NUM>) and a second coil (<NUM>) in spaced positions on a catheter body (<NUM>) of the catheter (<NUM>);
a driver (152A) coupled by a wired communication link to the first coil (<NUM>), wherein the driver (152A) is configured to transmit a first signal to the first coil (<NUM>);
a receiver (152B) coupled by a wired communication link to the second coil (<NUM>), wherein the receiver (152B) is configured to receive a second signal from the second coil (<NUM>) indicative of a proximity of the first coil (<NUM>) and the second coil (<NUM>); and
a signal analyzer (<NUM>) coupled by a wired or wireless communication link to the receiver (152B) that is configured to receive the second signal from the receiver (152B) and determine whether there is a change in the second signal indicative of a formation of the loop and/or the knot in the catheter (<NUM>).