LOW NOISE CABLE PROVIDING COMMUNICATION BETWEEN ELECTRONIC SENSOR COMPONENTS AND PATIENT MONITOR

Abstract

A physiological measurement system can include a low noise patient cable that connects a monitor and a noninvasive optical sensor. The cable has a plurality of emitter wires configured to communicate a drive signal between the monitor and at least one emitter. The cable also has a plurality of detector wires configured to communicate a physiological signal between at least one detector responsive to the emitter and the monitor. The emitter and detector wires are orthogonally disposed so that crosstalk between the two functionally different wires is mitigated.

Description

PRIORITY CLAIM

[0001] This application is a continuation of U.S. patent application Ser. No. 13/536,881, filed Jun. 28, 2012, pending, which claims a priority benefit under 35 U.S.C. .sctn.119(e) from U.S. Provisional Patent Application Ser. No. 61/502,740, filed on Jun. 29, 2011, titled "Low Noise Patient Cable" The '740 provisional application is incorporated by reference herein in its entirety.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present application is related to U.S. Publication No. 2003/0212312, filed on Dec. 19, 2002, entitled "Low Noise Patient Cable," which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE DISCLOSURE

[0003] 1. Field of the Disclosure

[0004] The present disclosure generally relates to patient monitoring devices and more specifically, embodiments of the present disclosure relate to cables connecting a monitor and a sensor of the patient monitoring device.

[0005] 2. Description of the Related Art

[0006] Physiological measurement systems using spectroscopic analysis are a widely accepted noninvasive procedure for measuring patient characteristics such as oxygen and glucose levels. Measuring these characteristics is important for patient wellness because for instance, an insufficient supply of oxygen can result in brain damage and death in a matter of minutes. Thus, early detection of low blood oxygen level is of crucial importance in the medical field, especially in critical care and surgical applications. Patient monitors commercially available from Masimo Corporation of Irvine Calif., USA, measure many physiological parameters including oxygen saturation, pulse rate, perfusion, carboxyhemoglobin, methemoglobin, total hemoglobin, glucose, overall wellness, respiration, combinations of the same and others.

[0007] As shown in FIGS. 1A and 1B, a physiological measurement system consists of a monitor 101, a noninvasive optical sensor 115 applied to a patient, and a cable 111 connecting the sensor and the monitor. The system is controlled using input keys. The monitor 101 may be a portable standalone device or may be incorporated as a module or built-in portion of a multiparameter patient monitoring system. The monitor displays measurements of various physiological patient characteristics on a display 105, which may include an oxygen saturation level, a pulse rate, and an audible indication of each pulse via a speaker 107. In addition, the monitor 101 may display the patient's plethysmograph, which is a visual display of the patient's pulse contour and pulse rate, as well as a myriad of other measurements and calculated parameters.

[0008] To perform the above functions, the monitor 101 energizes one or more emitters in the sensor 115 that irradiate tissue under observation, such as, for example, a finger, toe, foot, hand, ear, forehead or the like. The radiation from the emitters is scattered and absorbed by the tissue such that some attenuated amount emerges and is detected through one or more detectors located in the sensor 115. The detector(s) produces one or more signal(s) indicative of the intensity of the detected attenuated radiation and forward the signal(s) to the patient monitor 101 for processing. The sensor 115 that houses the emitters and the detectors can be disposable, reusable, or partially reusable and disposable. Reusable sensor may include a clothespin-shaped housing that includes a contoured bed conforming generally to the shape of a finger. The emitter and detector signals are transmitted over the cable 111 connecting the monitor and the sensor.

[0009] Depending on the nature of cables and the signals that are transmitted through cables, cables can be affected by a phenomenon known as crosstalk. Crosstalk occurs when energy from one signal interferes with another signal. Such interference can cause significant distortion in the transmission of information which can lead to incorrect measurements in physiological monitoring applications. As the cable 111 often communicates high voltage emitter driving signals and low voltage sensitive detector signals, the cable 111 may unfortunately cause unwanted interference on the sensitive detector signals used to determine measurements of the physiological parameters.

SUMMARY OF THE DISCLOSURE

[0010] The present disclosure provides a low noise tinsel cable arrangement particularly suited for transmitting communications between devices. In an embodiment, the cable is used to transmit electrical signals between a physiological sensor and a physiological monitor.

[0011] In an embodiment, the cable has one or more emitter wires configured to communicate drive signals between a monitor and at least one emitter. The cable also has one or more detector wires configured to communicate a physiological signals between at least one detector and the monitor. The emitter wires transmit relatively high energy drive signals, while the detector wires transmit lower energy physiological signals. Due to the effect of crosstalk, the high energy drive/emitter signals can distort the lower energy physiological/detector signals.

[0012] This is especially problematic because, unlike the known emitter drive signals generated by the monitor, the lower energy detector signal is an unknown signal. The unknown detector signal carries the important physiological patient information, such as, for example, signals responsive to absorption signals from the detector. Often, such absorption signals are lower energy signals and thus, often are more easily distorted. Thus, reducing interference with the detector signals improves system accuracy and reliability.

[0013] Existing solutions to reduce crosstalk on the detector signals include use of different twist rates and heavy shielding in a cable. Different twist rates of wire pairs do not fully mitigate crosstalk because at certain points in the cable, the electromagnetic forces of the signals may still interact to cause interference. While a heavy shield between the wires could potentially reduce the majority of the crosstalk, this makes the cable stiff and thick. A bulky, cumbersome cable may pull the sensor away from an ideal position on the patient or pull it off altogether, leading to erroneous physiological patient information. Moreover, heavy shielding is also more susceptible to stress fractures from flexing of the cable, leading to a short lifespan. Thus, at least because of the foregoing, heavy shielding is at least somewhat of an impractical solution for communicating signals from a sensor to a spectroscopic analysis device.

[0014] The present disclosure describes mitigating crosstalk by twisting the emitter wires about the central axis of the cable in an opposing rotational direction relative to the detector wires. Opposing twists advantageously seeks to create an angle between the two functionally different wires that approaches 90 degrees. At such an angle, crosstalk is reduced without requiring heavy shielding. One embodiment twists the detector wires in one direction down the center of the cable. The detector wires are insulated with an inner shield. Then the emitter wires are twisted in another direction around the inner shield such that the angle between the emitter wires and the detector wires is about 90 degrees. Put in other terms, the detector wires are twisted clockwise and the emitter wires are twisted counterclockwise, or vice versa. The emitter wires are insulated with an outer shield, and a jacket is disposed over the outer shield to form the cable.

[0015] The disclosed opposing rotation of the wires mitigates crosstalk from the opposing rotation. This may be without or in addition to different twist rates or shielding. Opposing rotation in the cable structure may provide a more flexible cable, thereby not hindering sensor placement of the patient.

[0016] In an embodiment, tinsel wires are used to form the cable. Tinsel wires are relatively thin and strong. Using tinsel wires allows the cable to be lighter and more flexible than equivalent all metal wires. While thinner wire is advantageous in some respects, reducing the cable diameter also increases the resistance through the wires. In an embodiment, the tinsel wires may also transmit the high energy drive signals. In such embodiments, the increasing resistance places some limitations on how small the cable diameter can be. The present disclosure accomplishes satisfactory signal transmission while simultaneously reducing the cable diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1A illustrates a perspective view of a physiological measurement system utilizing a noninvasive optical sensor.

[0018] FIG. 1B illustrates a perspective view of a portable physiological measurement system utilizing a noninvasive optical sensor.

[0019] FIG. 2 illustrates a perspective view of an embodiment of an uncoated tinsel cable.

[0020] FIG. 3 illustrates a perspective view of an embodiment of a coated tinsel cable.

[0021] FIG. 4 illustrates a cross sectional view of an embodiment of a low noise patient cable.

[0022] FIG. 5 illustrates a top-down view of an embodiment of the cable of FIG. 4.

[0023] FIG. 6 illustrates a cross sectional view of an embodiment of a low noise patient cable.

[0024] FIG. 7 illustrates a block diagram of a simplified embodiment of a kink testing apparatus for a cable.

[0025] FIG. 8 illustrates the testing apparatus of FIG. 7 with the cable in a stretched position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] As shown in FIGS. 1A and 1B (described in more detail below), a physiological measurement systems 100 includes a monitor 101, a cable 111, and a sensor 115. The sensor 115 can be any type of physiological sensor. Illustrated in FIGS. 1A and 1B are embodiments of noninvasive optical sensors. In the case of noninvasive optical sensors, the monitor 101 sends drive signals to one or more emitters in the sensor 115 via the cable 111. The emitters irradiate tissue under observation. One or more detectors in the sensor 115 detect the radiation leaving the tissue and send a signal back to the monitor via the cable responsive to the attenuation. This sequence produces more accurate results when the noninvasive optical sensor 115 remains substantially fixed with respect to the tissue of the patient. In the embodiment where the sensor 115 comprises a reusable sensor, the sensor 115 is often held in place by only the spring action of a clothespin-shaped housing. When a cable is stiff or bulky, as a patient moves to, for example, reposition themselves, the torque from the stiff or heavy cable may be more than the tension provided by the spring, thus even slightly shifting the optical components with respect to the measurement site on the tissue. A shifted or dislodged sensor could lead to erroneous physiological patient information.

[0027] As discussed in the foregoing, a stiff or bulky cable may be the result of utilizing heavy shielding to reduce damaging crosstalk. Crosstalk occurs when the drive/emitter signals interfere with the physiological/detector signals, potentially leading to erroneous physiological patient information, similar to but for different reasons a shifted or dislodged sensor. Thus, a low noise patient cable according to the present disclosure advantageously balances reduction of stiffness and size against the competing goal of reducing crosstalk.

[0028] Various embodiments described herein disclose a cable that is relatively thin and flexible, yet is still able to mitigate crosstalk. One embodiment includes the emitter wires twisted around the detector wires such that the angle between the two functionally different wires is within a range that creates a measurable difference in crosstalk. In an embodiment, the angle is about 90 degrees. In other embodiment, the angle ranges to either side of about 90 degrees where the reduction in crosstalk is measurable and advantageous in order to accommodate other design goals, such as, for example, flexibility, shielding, etc.

[0029] By controlling the angle between the differing cables, the presently disclosed low noise cable advantageously reduces harmful crosstalk before considering additional gains that can be accomplished using different twist rates or heavy shielding.

[0030] Additionally, embodiments of the present disclosure include tinsel wires and Kevlar material. Such construction materials advantageously provide a cable structure that is relatively thin and flexible, yet strong. It is noteworthy that the Applicants recognize that use of increasingly smaller diameter cable is not necessarily the natural progression of innovation in medical cabling like the smaller is better concepts from semiconductor fabrication. In contrast to semiconductor fabrication, in patient cabling innovation, reducing the cable diameter most often increases the resistance through the thinner wires. Thus, as a cable diameter shrinks, the spectroscopic analysis devices become inoperable as signals cannot be effectively or even operably transmitted due to the increase cable properties such as resistance.

[0031] Embodiments of the low noise cable described herein balance the issues of cable diameter, resistance, shielding, etc. to disclose a cable that is thin and flexible, yet still able to effectively communicate the desired signals. This thin and flexible cable structure that mitigates crosstalk advantageously increases accuracy and reliability.

[0032] FIG. 2 illustrates a simplified perspective view of an embodiment of an uncoated tinsel cable 200. Tinsel cables as used herein include their ordinary broad meaning understood by an artisan and, from the disclosure herein, include a non-conductive fiber 201, such as, for example, aramid fiber, that is coated with a thin layer of twisted conductive material 203. In an embodiment, the conductive material 203 is a silver copper alloy. The non-conductive fiber 201 provides strength and flexibility, while the conductive material 203 allows transmission of electrical signals. The conductive layer 203 is made very thin such that flexes in the cable 200 do not cause fatigue.

[0033] FIG. 3 illustrates a simplified perspective view of an embodiment of a coated tinsel cable 300. The coated cable 300 includes the same or similar materials as the uncoated tinsel cable 200, but includes a plastic outer coating 205. In an embodiment, the plastic outer coating 205 includes fluorinated ethylene propylene (FEP). An artisan will recognize from the disclosure herein that other constructions seeking to elevate associated advantages may also be used.

[0034] FIG. 4 illustrates a simplified embodiment of a cross sectional view of each end of a low noise cable 400 according to portions of the present disclosure. The cable 400 includes an outer non-conductive protective jacket 401, an outer shield layer 403, an outer core 405, an inner shield 407, an inner core 409 and fiber filler 411. The outer non-conductive protective jacket 401 is made of flexible insulation. In an embodiment, the protective jacket 401 is UV resistant polyurethane and has a diameter of about 4.0 mm. The outer shield layer 403 is made of twisted uncoated tinsel cable. The outer core 405 is made of a single layer of twisted coated tinsel cable. The inner shield 407 is again made of twisted uncoated tinsel cable. The inner core 409 is also again made of twisted coated tinsel cable, but also includes fiber fill 411 to provide some structure to the inner core and to provide tensile strength to help prevent the cable from tearing apart. In an embodiment, the fiber fill is made of Kevlar to provide added strength. In an embodiment, the fiber fill is made of aramid fiber. In an embodiment, as illustrated in FIG. 4, the cable has six fiber fill strands 411.

[0035] In an embodiment, as illustrated in FIG. 4, there are fifteen outer core wires 405 and fifteen inner core wires 409. In other embodiments, more or fewer wires could be used depending on the application of the cable and the number of transmission paths needed. The various wires in the inner and outer cores 405 and 409 can have different colors of insulation for easy identification.

[0036] In order to minimize crosstalk, the inner core 409 and the outer core 405 are twisted in opposing rotational directions. FIG. 5 illustrates the manner in which, in embodiments disclosed herein, wires in an inner core are twisted in an opposing fashion relative to wires in an outer core. FIG. 5 shows a simplified top-down view of a cable 500, which includes inner wires 502 in an inner core twisted about the central axis of the cable 500 in a helical fashion. The cable 500 also includes outer wires 504 in an outer core, which are also twisted about the central axis of the cable 500 in a helical fashion but in an opposing rotational direction from the inner wires 502. The angle .theta. shown in FIG. 5 indicates the angle between the outer wires 504 and the inner wires 502. Interference and crosstalk between the outer wires 504 and the inner wires 502 are reduced as the angle .theta. approaches 90 degrees from either direction.

[0037] For example, in one embodiment, the inner core is twisted clockwise and the outer core is twisted counter clockwise. This arrangement causes the outer core cables to be at about an angle of greater than 90 degrees to inner core cables, assisting in reducing crosstalk. In an embodiment, the angle is between about 60 and about 120 degrees. In another embodiment, the angle is between about 60 and about 90 degrees, and in a further embodiment, the angle is about 90 degrees. In still another embodiment, the angle is about 60 degrees.

[0038] In an embodiment, the inner core is used to transmit the relatively low voltage detector signals back to the monitor and the outer core is used to transmit the relatively high voltage emitter drive signals. In an embodiment, the emitter wires are the inner core wires and the detector wires are the outer core wires.

[0039] FIG. 6 illustrates another embodiment of a low noise sensor cable. In this embodiment, tinsel cables are used in conjunction with standard wires, such as copper wires. In the outer core 605, there are four sets of three tinsel wires 635 and four sets of two standard wires 637 that can be any standard conducting wire such as copper. The inner core 609 includes a set of triple twisted tinsel wires 641, four sets of twisted pair tinsel wires 639 and three standard detector wires 643. As in the embodiment of FIG. 4, the inner core 609 of the FIG. 6 embodiment includes a fiber fill strand 411 to enhance the structure and tensile strength of the cable. An inner shield layer 607 separates the inner core wires from the outer core wires. An outer shield layer 603 surrounds the outer core 605. A jacket 601 is disposed over the outer shield to form the cable.

[0040] Embodiments described herein show enhanced resilience to mechanical stresses, such as kink resistance. Cables described herein and illustrated in FIG. 4 were tested to determine their resistance to electrical failure due to mechanical breakdown of the internal conductors and/or shielding after the cable is subjected to repeated attempted kinking. FIG. 7 illustrates the test setup. The setup includes a cable 700 secured into, for example, two mounting blocks 710, 712. A section of, for example, at least about twelve (12) inches of cable 700 is used for testing. Before the cable 700 is secured to the mounting blocks 710, 712, two positions on the cable 700 approximately seven to eight inches apart are marked, and the cable 700 is grasped at those marks and twisted approximately 720 degrees. This twisting causes the cable to form a loop 740 as shown in FIG. 7, and the cable 700 is then secured to the mounting blocks 710, 712 at the marked positions.

[0041] The mounting blocks 710, 712 are attached to a track 718. The first mounting block 710 is fixed to the track 718, and the second mounting block 712 is slidably attached to the track 718. The second mounting block is also attached to a guide block 722, which is in turn driven by a pneumatic cylinder 724. The pneumatic cylinder 724 receives an air supply of approximately about 100 psi, which is regulated down to about 50 psi. This arrangement allows a tensile force of approximately 5-7 lbf. to be applied to the cable 700. When the pneumatic cylinder 724 pushes the guide block 722 and then pulls it back to the starting position, this constitutes one cycle of the test.

[0042] FIG. 7 shows the testing apparatus when the pneumatic cylinder 724 is at its starting position. Because no tensile force is being applied to the cable 700, the loop 740 is present. FIG. 8 shows the same testing apparatus when the pneumatic cylinder 724 is pushing on the guide block 722, therefore applying a tensile force to the cable 700. The effect of this tensile force is to attempt to produce a kink 742 in the cable 700.

[0043] The two ends 702, 704 of the cable 700 are electrically connected to a break detect circuit test box 730. The box 730 senses when a significant change of resistance occurs in the cable 700, and when this occurs, the box 730 sends a signal to the pneumatic cylinder 724 to stop the testing. Thus, this test repeatedly subjects the cable 700 to kinking until an electrical failure occurs. The number of cycles the cable 700 can withstand before electrical failure is an indicator of its resilience to mechanical stresses.

[0044] Twelve cable samples were subjected to this test. The results of the testing are shown below:

TABLE-US-00001 Sample Cycles to Failure 1 13,820 2 6,831 3 12,053 4 9,781 5 8,493 6 6,808 7 9,232 8 23,781 9 18,842 10 15,205 11 15,248 12 17,395

[0045] As the table shows, the smallest number of cycles producing an electrical failure for the twelve samples tested was 6,808 cycles and the largest was number of cycles was 23,781. The mean cycles-to-failure was 13,124 and the median was 12,937. These results demonstrate that the cable described herein exhibit enhanced resilience to mechanical stress. Cables described herein are capable of withstanding more than 1,500 kinks with a high degree of reliability. Reliability can be measured using a Weibull Distribution Model. Applying that model with a shape parameter of Beta=1.7, in order for the cable to reliably withstand 1,500 kinks, none of the twelve samples tested should have a failure after 6,583 kink cycles. Because the smallest number of cycles producing an electrical failure for the twelve samples tested was 6,808 cycles, the cable tested is capable of withstanding more than 1,500 kinks with a high degree of reliability. The cables described herein are capable of withstanding, on average, more than 5,000 kinks. More particularly, the cables described herein are capable of withstanding, on average, more than 10,000 kinks. Still more particularly, the cables described herein are capable of withstanding, on average, more than 12,500 kinks. In an embodiment, the cables described herein are capable of withstanding in the range or 0 to 23,000 kinks.

[0046] FIGS. 1A and 1B illustrate perspective views of physiological measurement systems utilizing a noninvasive optical sensor. Referring specifically to FIG. 1A, the physiological measurement system 100 has a portable monitor 101 and docking station 103 that houses the portable monitor 101. The portable monitor 101 has a display 105 to show physiological measurement data. The measurement data provides a readout of blood analytes, such as oxygen, carbon monoxide, methemoglobin, total hemoglobin, glucose, proteins, glucose, lipids, a percentage thereof (e.g., saturation), or other physiologically relevant patient characteristics. The portable monitor also has a speaker 107 to provide audible monitoring of physiological measurements, including, for example, the pulse rate. Utilizing control buttons, a user can operate the physiological measurement system and select between different available measurement data or other functionality for the user to manipulate, such as alarm settings, emitter settings, detector setting, and the like.

[0047] A cable 111 docks into a monitor sensor port 113 and connects to a noninvasive optical sensor 115 that is fitted on a patient utilizing a clothespin-shaped enclosure with a contoured bed conforming generally to the shape of a finger. The cable 111 can be of various lengths to allow for separation between the portable monitor 101 and sensor 115. The noninvasive optical sensor 115 has a set of emitters and detectors. The emitters serve as the source of optical radiation to irradiate patient tissue. The portable monitor 101 sends a drive signal to the emitters via the monitor sensor port 113 and through the cable 111. The emitters produce optical radiation using one or more sources of optical radiation, such as LEDs, laser diodes, incandescent bulbs with appropriate frequency-selective filters, combination of the same, or the like. The radiation from the emitters is scattered and absorbed by the tissue such that some attenuated amount emerges and is detected by one or more detectors. The detectors produce a signal indicative of the intensity of the detected attenuated radiation and forward the signal via the cable through the monitor sensor port to the portable monitor for processing.

[0048] FIG. 1B illustrates a perspective view of another portable physiological measurement system 150 utilizing a noninvasive optical sensor 151. The system of FIG. 1B is similar to that of FIG. 1A described above except that the monitor 155 is a portable standalone device instead of being incorporated as a module or built-in portion of the physiological measurement system. Moreover, the physiological measurement system 150 in FIG. 1B includes advanced functionality involving additional emitter and detectors in the sensor 151. This allows the patient physiological measurement system 150 to determine more difficult to detect parameters such as, for example, glucose and total hemoglobin. Moreover, the cable 153 is required to transmit more sensitive data that is easily corrupted by cross talk and other interference. As a result, the cabling described in the present disclosure is particularly suited to use in the patient monitor of FIG. 1B. The monitor 155 has a display 157 to show physiological measurement data and control buttons 159 that allow a user to operate the physiological measurement system 150 and select between different available measurement data or other functionality.

[0049] The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared, as used above, means that some or all code from multiple modules may be executed using a single (shared) processor. In addition, some or all code from multiple modules may be stored by a single (shared) memory. The term group, as used above, means that some or all code from a single module may be executed using a group of processors. In addition, some or all code from a single module may be stored using a group of memories.

[0050] The apparatuses and methods described herein may be implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on a non-transitory tangible computer readable medium. The computer programs may also include stored data. Non-limiting examples of the non-transitory tangible computer readable medium are nonvolatile memory, magnetic storage, and optical storage.

[0051] Although the foregoing invention has been described in terms of certain preferred embodiments, other embodiments will be apparent to those of ordinary skill in the art from the disclosure herein. For example, additional or alternative materials may be used to enhance the low noise cable for the known properties of the additional or alternative materials without detracting from the novelty of the present disclosure. Moreover, different or additional testing apparatuses than those of FIGS. 7 and 8 may provide useful insight into the flexibility and/or noise reduction of the present disclosure. Additionally, other combinations, omissions, substitutions and modifications will be apparent to the skilled artisan in view of the disclosure herein. Accordingly, the present disclosure is not intended to be limited by the reaction of the preferred embodiments, but is to be defined by reference to the appended claims.

[0052] Additionally, all publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

Claims

1. A low noise patient cable comprising: a plurality of detector wires configured to communicate a physiological signal between a detector, which is responsive to energy received from an emitter, and a monitor; a shield disposed over the plurality of detector wires; a plurality of emitter wires configured to communicate a drive signal between the monitor and at least one emitter, wherein the plurality of emitter wires are twisted in an opposing rotational direction relative to the plurality of detector wires; and a jacket comprising the plurality of detector wires, the shield, and the plurality of emitter wires, wherein a thickness of the shield is less than or equal to 4 mm.

2. The low noise patient cable of claim 1, wherein an angle between the plurality of emitter wires and the plurality of detector wires is between about 60 degrees and about 90 degrees.

3. The low noise patient cable of claim 2, wherein the plurality of detector wires are tinsel wires.

4. The low noise patient cable of claim 2, further comprising a plurality filler wire.

5. The low noise patient cable of claim 4, wherein the plurality filler wires comprise at least one of the following: kevlar wires and aramid wires.

6. The low noise patient cable of claim 2, further comprising a second shield disposed over the plurality of emitter wires.

7. (canceled)

8. A method of making a cable, the method comprising: twisting in a first direction a plurality of inner core wires; using a shield over the plurality of inner core wires that does not limit flexibility of the cable; twisting in a second direction a plurality of outer core wires around the shield, the second direction being opposite the first direction; and disposing a jacket around the plurality of outer core wires.

9. The method of claim 8, further comprising twisting a plurality of filler wires with the plurality of inner core wires.

10. The method of claim 8, further comprising disposing a second shield around the plurality of outer core wires.

11. The method of claim 8, further comprising twisting a plurality of filler wires with the plurality of inner core wires.

12. The method of claim 11, wherein the filler wires are aramid.

13. The method of claim 11, wherein the filler wires are Kevlar.

14. The method of claim 8, wherein the inner and outer core wires are tinsel wires.

15. The method of claim 14, wherein the tinsel wires are made from a silver copper alloy.

16. A low noise patient cable comprising: a plurality of inner core wires twisted about a central axis of the cable in a first direction, the plurality of inner core wires being configured to communicate a first electrical signal; a shield disposed over the plurality of inner core wires, the shield having a thickness that maintains flexibility of the plurality of inner core wires and the outer core wires, wherein the thickness is less than or equal to a diameter of a jacket; a plurality of outer core wires twisted about the central axis in a second direction, the second direction being opposite the first direction, wherein the plurality of outer core wires are configured to communicate a second electrical signal, wherein the low noise patient cable does not electrically fail after being kinked more than 1,000 times.

17. The low noise patient cable of claim 16, wherein the plurality of inner core wires are tinsel wires.

18. The low noise patient cable of claim 17, wherein the tinsel wires are a silver copper alloy.

19. The low noise patient cable of claim 16, further comprising a plurality filler wires twisted with the inner core wires.

20. The low noise patient cable of claim 16, further comprising a second shield disposed over the plurality of outer core wires.

21.-27. (canceled)

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