Patent Application
20230113963
The present disclosure generally relates to neuromuscular monitoring of patients, and more particularly to a kinemyography sensor and monitoring system.
Neuromuscular transmission (NMT) is the transfer of an impulse between a nerve and a muscle at the neuromuscular junction. An NMT may be blocked in a patient, such as a patient undergoing a surgical procedure by neuromuscular blocking agents/drugs. Neuromuscular blocking agents cause transient muscle paralysis and prevent the patient from moving spontaneously.
It is often desirable to monitor the level of neuromuscular block in a patient to ensure that appropriate block is provided for a given procedure and also to limit the amount of neuromuscular blocking agent administered to a patient to the minimum amount needed to achieve the desired level of paralysis. Patient monitoring systems, and specifically neuromuscular transmission monitoring systems, are utilized to determine a patient's muscle response, and thus the level of neuromuscular block experienced by a patient. Several types of neuromuscular transmission (NMT) monitoring systems are available, including electromyography systems, kinemyography systems, and acceleromyography systems, to name a few. NMT monitors utilize an electrical stimulus provided to a patient's motor nerve and measure a muscle response thereto. Typically, the stimulus is provided to a patient's ulnar nerve near the wrist and the response of the muscle near the thumb, the adductor pollicis, is monitored. The evoked muscle responses are monitored via any of several methods listed above. In kinemyography, the degree of distortion, or bending, of the sensor due to the muscle response, such as at the patient's thumb, is measured.
In clinical settings, the nerve stimulator is often attached to a patient (e.g., on the patient's skin above the ulnar nerve) and an electrical stimulation current is applied to the patient before induction of the anesthesia or immediately thereafter. Thereby, a baseline value response is recorded by the NMT monitor and used to normalize the muscle response once the muscle relaxant is administered. Evoked muscle responses are then monitored, such as throughout the surgical procedure, to determine the patient's level of neuromuscular blockage.
This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
In one embodiment, a kinemyography sensor includes a support frame and a flexible substrate, wherein at least a portion of the flexible substrate is attached to the support frame. The support frame is configured to attach to a patient's thumb and forefinger and has a bendable middle section configured to bend in response to movement of the patient's thumb. A printed stimulation circuit is printed on the substrate and includes a pair of stimulation electrodes configured to adhere to a patient's skin to deliver a kinemyography stimulus, and a printed bend sensor is printed on the substrate and located on the bendable middle section of the support frame, wherein the printed bend sensor is configured to sense the bending of the support frame.
In one embodiment, a kinemyography sensor includes a flexible substrate having a stimulation section, a sensor section, and a connection section. The stimulation section has a pair of stimulation electrodes printed thereon and configured to adhere to a patient's skin to deliver a kinemyography stimulus. The sensor section has a printed bend sensor printed thereon, wherein the printed bend sensor is configured to be positioned between a patient's thumb and forefinger to sense movement of the patient's thumb. The connection section is at a first end of the substrate, the connection section having a plurality of contact pads printed thereon and configured to mate with a sensor connector of a neuromuscular transmission monitoring device.
In one embodiment, a neuromuscular transmission monitoring system includes a kinemyography sensor and a neuromuscular transmission monitoring device having a sensor connector configured to removably mate with a first end of the kinemyography sensor so as to receive sensing signals therefrom. The kinemyography sensor includes a flexible substrate having a stimulation section, a sensor section, and a connection section. The stimulation section has a pair of stimulation electrodes printed thereon and configured to adhere to a patient's skin to deliver a kinemyography stimulus. The sensor section has a printed bend sensor printed thereon and configured to sense movement of the patient's thumb in response to the stimulus, wherein the printed bend sensor is a resistive sensor or a piezoelectric sensor. The connection section is at the first end of the substrate and is configured to electrically connect to the sensor connector.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.
The drawings illustrate the best mode presently contemplated of carrying out the disclosure. In the drawings:
Kinemyography (KMT) measures a muscle response of a patient based on the amount of distortion or bending induced by a patient's muscle response on a bend sensor. A bend sensor may be placed between the thumb and forefinger on a patient where the electrical stimulation is delivered to a patient's ulnar nerve or a patient's median nerve at the patient's wrist. Current kinemyography sensors are reusable sensors that are used with multiple patients over a relatively long service life.
The inventor has recognized that current reusable kinemyography sensors are problematic for several reasons. First, they pose a contamination risk due to their use by multiple patients. Further, reusable sensors are prone to breakage and sensing accuracy degradation over their long service life, sometimes breaking or malfunctioning in undetectable ways resulting in undetected inaccuracies in the sensing output.
In view of the foregoing problems and challenges in the relevant art, the inventor has developed the disclosed single-use kinemyography sensor that can be manufactured for relatively low cost, provides an intuitive form factor, and yields reliable and replicatable measurements. The disclosed sensor is a printed kinemyography sensor wherein the stimulation circuit and the bend sensor are both incorporated onto a single flexible substrate to be attached to the patient's hand and wrist. The disclosed printed kinemyography sensor utilizes screen printing or other flexible printing techniques and enables printing of both the stimulation circuit and the sensing circuit in one process step, or in some embodiments in only a few process steps depending on the type of bend sensor utilized. The single-piece kinemyography sensor minimizes opportunities for assembly mistakes and damage during transport and is easy and intuitive to apply to the patient.
The printed kinemyography sensor 20 further includes a connection section 34 adjacent to the first end 31 of the substrate that is configured to mate with and electrically connect to a sensor connector 14 of the NMT monitoring device 2. More particularly, the connection section 34 includes multiple printed contact pads that are configured to electrically connect to corresponding contacts in the sensor connector 14 of the NMT monitoring device 2. The connection section 34 is configured to mate with the connection port 16 of the sensor connector 14, which in the depicted embodiment is performed by sliding the connection section 35 at the first end 31 of the flexible substrate 30 into the sensor connection port 16 of the sensor connector 14. Thus, the connection port 16 is configured to receive the connection section 35. In other embodiments the connection section 35 may include a connector, such as a non-printed male or female connection end, that is attached to the substrate 30 and configured to mate with the sensor connector 14.
The sensor connector 14 is at the end of a cable 12. At the opposing end of the cable 12 is a device end 13 that connects to the NMT monitoring device 2. The NMT monitoring device 2 includes a housing 3 with a sensor port 7 configured to mate with the device end 13 of the cable 12. In the depicted embodiment, the housing 3 also holds a display 4 and a user input element 5. The user input element 5 may be configured to allow a user to control function of the NMT monitoring system 1, including to initiate a measurement on the patient and/or to control a mode of the monitoring device 2, such as to instruct automatic periodic NMT measurement on the patient.
The NMT monitoring device 2 is configured to process the electrical signals received from the kinemyography sensor 20 and to determine a level of neuromuscular blockage for the patient. In one embodiment, the NMT monitoring device 2 is configured to determine a train of four (TOF) of the patient. The measured and determined level of neuromuscular blockade may be displayed on the display 4, which in the depicted example is displayed as a number of detected muscle responses for forced stimulation and as a percentage.
The kinemyography sensor 20 shown in
The support frame 22 may be a curved shape piece, such as having a first leg 25 configured to attach to the patient's thumb and a second leg 27 configured to attach to the patient's forefinger. In the depicted example, the support frame 22 is attached to the patients thumb and forefinger by finger prongs 26 and 28. Specifically, the first leg 25 has a first set of finger prongs 26 configured to clasp or wrap around a patient's thumb. The second leg 27 has a set of finger prongs 28 configured to clasp or wrap around the patient's forefinger. Thereby, the support frame 22 is held in place on the patient's hand.
The flexible substrate 30 is attached to the support frame 22 such that the printed bend sensor 62 is located on the bendable middle section 24 of the support frame 22. More particularly, the sensor section 38 on which the printed bend sensor 32 is mounted is attached to the middle section 24 of the support frame 22, such as adhered thereto. The sensor 38 may be attached to the bendable middle section 24 with an adhesive, such as double-sided pressure-sensitive adhesive tape with acrylic adhesive. The adhesive is located between the support frame and flexible substrate as to not be exposed to user and may be applied over the entirety of the sensor section 38 including over the bend sensor 62, for example, or may be applied around the edges of the sensor section 38, such as to avoid the area of the printed bend sensor 62.
Referring also to
The stimulation section 36 and the sensor section 38 may be variously arranged on the elongated substrate 30. The shape of the elongated substrate 30 and the position of leadwires are adjusted accordingly, and various shapes and lead wire arrangements are within the scope of the present disclosure.
In both embodiments, the shapes of each of the stimulation section 36 and the sensor section 38 may be adjusted as appropriate for a particular design and attachment to the patient. Similarly, the proportions and lengths of the first lead section 35 and the second lead section 37 may also be adjusted such that the stimulation section 36 is easily positionable on a patient's wrist and the sensor section 38, which is connected to the support frame 22, is comfortably positioned on a patients thumb and forefinger with enough slack that the patient can rotate their hand and wrist without undue restriction. The sensor may be sufficiently long and proportioned to accommodate a range of patients and various patient physiologies. In certain embodiments, multiple sensor sizes may be manufactured, and lengths and proportions of the various substrate sections 34-38 may be adjusted accordingly.
The simulation circuit 50 includes a pair of stimulation electrodes 41 and 42 and corresponding stimulation leadwires 51 and 51 and contact pads 53 and 54. Referring to
The elements of the stimulation circuit 50 are printed on the substrate 30 with a conductive ink, such as a silver-based conductive ink. In certain embodiments, the electrode pads 46, 47 may be printed with a silver/silver chloride (Ag/AgCl) ink that provides increase conductivity for delivering the stimulation current to the patient. In certain examples, the electrode pads 46, 47 may consist of two printed layers, including a first conductive ink and a second conductive ink.
A dielectric layer may be printed on top of the leadwire portions of the circuit 50, avoiding the electrode pads 46 and 47 and the contact pads 53 and 54, to isolate the circuit. Electrode gel is applied on top of the electrode pads 46 and 47. The first electrode gel pad 48a is applied over a first electrode pad 46 and a second electrode gel pad 48b is applied over the second electrode pad 47. In one embodiment, the electrode gel 48a, 48b may be printed on top of the respective electrode pads 46, 47.
An adhesive pad 44 is assembled onto the stimulation section 36 of the substrate 30, which may cover over at least a portion of the stimulation leadwires 51 and 52 but avoiding the stimulation electrodes 41 and 42. As shown in the figures, adhesive pad 44 is shaped to cover the stimulation section 36 of the substrate 30 and has two holes therein where each of the stimulation electrodes 41 and 42 are located. For example, the adhesive pad 44 may be a foam pad with adhesive on the bottom side 45 configured to adhere to a patient's skin. Thereby, the adhesive pad 44 attaches the electrodes 41 and 42 to the patient's skin. In certain embodiments, the thickness of the adhesive pad 44 is equal to or slightly less than the total thickness of the stimulation electrodes 41 and 42. Thus, the electrode gel 48a, 48b is flush with or slightly protruding from the bottom surface 45 of the adhesive pad 44.
Referring again to
The bend sensor 62 is printed on the substrate 30, and specifically on the sensor section 38 thereof. The printed bend sensor is configured such that bending of the sensor section 38 in reaction to movement of the patient's thumb causes changes in the sensor that enable movement detection and/or measurement of the magnitude of movement.
The resistive bend sensor 62a is configured to change resistance when bent so as to enable measurement of the movement of the patient's thumb. When attached to the support frame 22, the resistive sensor 62a bends with the bendable middle section 24 due to movement of the patient's thumb. As the resistive bend sensor 62a bends, the resistance progressively increases as the magnitude of the bend increases.
As the resistive bend sensor 62a is bent due to movement of the patient's thumb, the cross section of the conductive ink layer 71 changes, thus changing the resistance. For the resistive embodiment, the NMT monitoring device 2 is configured to measure resistance across the resistive bend sensor 62a at predetermined intervals following a stimulation so as to measure the change in resistance a plurality of times throughout the resulting movement of the patient's thumb so as to measure a magnitude thereof.
Alternatively, the printed bend sensor 62 may include a printed piezoelectric bend sensor 62b configured to produce a charge when it is bent. Namely, deformation of the piezoelectric material in the sensor produces an electric charge resulting from the piezoelectric effect. This charge can be measured as an indicator of the bend magnitude, and thus the magnitude of movement and muscle response in the patient's thumb. The NMT monitoring device 2 receives and samples the charge a plurality of times throughout the resulting muscle response to as to measure a magnitude thereof.
In the embodiment depicted in
A dielectric ink layer 78 is printed or otherwise applied over the second conductive ink layer 77 to isolate and protect the conductive ink layer. In certain examples, the dielectric layer 78 may be printed over just the second conductive ink layer 77 or may be printed over the entire sensor section 38, and/or over the first and/or second lead sections 35 and 37 of the substrate 30 as well.
The layer configuration depicted in
In some embodiments, an adhesive layer may be applied over the top of the printed bend sensor 62 to adhere the printed bend sensor to the support frame 22, for example.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
