BACKGROUND

[0001] Endotracheal tubes include electrodes that are designed to make contact with a patient's vocal cords to facilitate electromyographic (EMG) monitoring of the vocal cords during surgery when connected to an EMG monitoring device. Endotracheal tubes provide an open airway for patient ventilation, and provide for monitoring of EMG activity of the intrinsic laryngeal musculature when connected to an appropriate EMG monitor. Endotracheal tubes can provide continuous monitoring of the nerves supplying the laryngeal musculature during surgical procedures.

SUMMARY

[0002] One embodiment is directed to an apparatus for monitoring EMG signals of a patient's laryngeal muscles. The apparatus includes an endotracheal tube having an exterior surface, and a tube coating applied to the exterior surface via spraying of a homogeneous solution onto the endotracheal tube or immersion of the endotracheal tube in the homogeneous solution. A conductive electrode is formed on the tube coating. The conductive electrode is configured to receive the EMG signals from the laryngeal muscles.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Figure 1 is a diagram illustrating an EMG endotracheal tube apparatus with a tube coating according to one embodiment.

[0004] Figure 2 is a diagram illustrating a cross-sectional view of the EMG endotracheal tube apparatus shown in Figure 1 according to one embodiment. [0005] Figure 3 is a flow diagram illustrating a method of applying electrodes to an

EMG endotracheal tube according to one embodiment.

[0006] Figure 4 is a flow diagram illustrating a method of monitoring EMG signals of a patient's laryngeal muscles according to one embodiment.

[0007] Figure 5 is a flow diagram illustrating a method of applying an electrode to an endotracheal tube according to one embodiment.

DETAILED DESCRIPTION

[0008] Figure 1 is a diagram illustrating an EMG endotracheal tube apparatus 100 with a tube coating according to one embodiment. Figure 2 is a diagram illustrating a cross-sectional view of the EMG endotracheal tube apparatus 100 shown in Figure 1 according to one embodiment. Endotracheal tube apparatus 100 includes solid wires 102, fitting 104, cuff inflating conduit 106, polymer endotracheal tube 110, electrodes 112, and cuff 114. In one embodiment, electrodes 112 are conductive ink electrodes that are printed on an electrode region 113 of the tube 110. Solid wires 102 are connected to electrodes 112 at interconnection 108.

[0009] Tube 110 transports gases to and from the lungs. Fitting 104 is configured to be connected to a respirating machine (not shown) for injecting air into the lungs and withdrawing air from the lungs. Cuff inflating conduit 106 is configured to be connected to a source of compressed air (not shown) for cuff 114. Cuff inflating conduit 106 communicates with a lumen 222 (Figure 2) located in the wall 220 of tube 110, and the lumen communicates with cuff 114.

[0010] After endotracheal tube 110 is inserted into the trachea of a patient, electrodes 112 sense EMG signals, which are output to an EMG processing machine, such as nerve integrity monitor (NFM) device 120, via solid wires 102. Die cut tape may be used to tape tube 110 to a patient's mouth to secure the tube and keep it appropriately positioned. [0011] As shown in Figure 2, lumen 222 is located in the tube wall 220 of tube 1 10 for inflating the cuff 1 14 (Figure 1). Tube coating 230 is formed on the outer surface of the tube wall 220. Conductive ink electrodes 1 12 are formed on the outer surface of the tube coating 230. In one embodiment, tube coating 230 is made from the following elements in the indicated proportions: 20g polyvinyl chloride (PVC) pellets; lOg cyclohexanone; 60g tetrahydrofuran (TFIF); 30g acetone; 60g ink thinner; and trace amounts of food grade colorant. In one embodiment, the PVC pellets are dissolved in a mixture of solvents, including the cyclohexanone, TUF, acetone, and ink thinner. The colorant is then added, and the resulting colored solution is sprayed on the tube 1 10 to form the tube coating 230. In some embodiments, the tube coating 230 has a coating thickness of about 10-100 microns.

[0012] The food grade colorant causes the tube 1 10 to have a color tint (e.g., a blue tint), with a transmittance of about 74-93%, as opposed to a clear tube with a transmittance of 100%. The transmittance may be varied by pigment, pigment concentration, and/or thickness of the tube coating 230. The color tint helps differentiate the coated tube from other EMG tubes, while still maintaining a high transmittance, which can be important for a monitoring tube. Different color tints may also be used to indicate different EMG tube sizes.

[0013] In some embodiments, tube coating 230 is only formed on the electrode region 1 13 (Figure 1) of the tube 1 10, and the remainder of the external surface of the tube 1 10 is not covered by tube coating 230. In other embodiments, tube coating 230 is formed on the entire outer surface of the tube 1 10, or substantially the entire outer surface of the tube 1 10 (e.g., 90 percent or more of the outer surface area of the tube 1 10).

[0014] In one embodiment, conductive ink electrodes 1 12 are formed by tracing or printing a silver filled polymer conductive ink on tube coating 230. Conductive inks are available in variety of flowable material choices such as Silver, Carbon, Gold, Platinum, Palladium, Silver-Tungsten, and Silver-Titanium. Conductive inks can be deposited on the coating 230 using various known technologies such as PAD printing, screen printing, ink jet dispensing, digital printing, Micropen dispensing, painting, vapor deposition, and plasma sputtering. Conductive inks can be used both for stimulation and recording purposes in nerve monitoring applications.

[0015] EMG endotracheal tubes may have some surface contamination that adversely affects the adhesion of electrodes to the tubes. Forming the electrodes 112 on the tube coating 230, rather than directly on the outer surface of the tube 110 provides several advantages, including improved adhesion, flexibility, resistance to cracking, and improved shelf life.

[0016] Figure 3 is a flow diagram illustrating a method 300 of applying electrodes to an EMG endotracheal tube according to one embodiment. At 302 in method 300, a solute is added to a container containing a mixture of solvents. In some embodiments, the solute comprises PVC pellets, and the solvents include cyclohexanone, TFIF, acetone, and ink thinner. At 304, the combination of the solvents and the solute is stirred or mixed with a magnetic stirrer until the solute dissolves to form a homogeneous solution. At 306, a colorant is added to the solution to form a colored solution.

[0017] At 308 in method 300, the outer surface of the EMG endotracheal tube is cleaned with alcohol to remove any residue. At 310, regions of the EMG endotracheal tube that are not to be coated are masked. At 312, the colored solution is sprayed on the EMG endotracheal tube in an aerosol form while the tube is being rotated to form a tube coating on unmasked regions of the outer surface of the tube. At 314, electrodes are formed on an outer surface of the tube coating. In one embodiment, the electrodes are formed from a silver conductive ink, and are printed on the outer surface of the tube coating at 314.

[0018] At 316, the EMG endotracheal tube with the tube coating and electrodes formed thereon goes through a baking process. In one embodiment, the tube coating is allowed to air dry, rather than being baked, before formation of the electrodes at 314, so the method 300 involves only a single baking process (i.e., after formation of the electrodes). [0019] In other embodiments, rather than spraying the colored homogeneous solution onto the EMG endotracheal tube, the tube is instead immersed in a bath of the colored homogeneous solution to form the tube coating.

[0020] One embodiment is directed to an apparatus for monitoring EMG signals of a patient's laryngeal muscles. The apparatus includes an endotracheal tube having an exterior surface, and a tube coating applied to the exterior surface via spraying of a homogeneous solution onto the endotracheal tube or immersion of the endotracheal tube in the homogeneous solution. A conductive electrode is formed on the tube coating. The conductive electrode is configured to receive the EMG signals from the laryngeal muscles.

[0021] The tube coating of the apparatus may cause the endotracheal tube to have a color tint. In one embodiment, the tube coating has a transmittance of about 74-93%. The tube coating may be applied only to an electrode region of the endotracheal tube. The tube coating may be formed from spraying the homogeneous solution in an aerosol form onto the endotracheal tube. The tube coating may be formed from PVC pellets dissolved in a mixture of solvents to form the homogeneous solution. The mixture of solvents may include cyclohexanone, tetrahydrofuran (THF), and acetone. The mixture of solvents may further include an ink thinner. The homogeneous solution may include a food grade colorant.

[0022] Another embodiment is directed to a method of monitoring EMG signals.

Figure 4 is a flow diagram illustrating a method 400 of monitoring EMG signals of a patient's laryngeal muscles according to one embodiment. At 402 in method 400, an endotracheal tube having a tube coating applied to an exterior surface of the endotracheal tube via spraying of a homogeneous solution onto the endotracheal tube or immersion of the endotracheal tube in the homogeneous solution, and having a conductive electrode formed on the tube coating, is provided. At 404, the EMG signals from the laryngeal muscles are sensed with the conductive electrode. At 406, the EMG signals sensed by the conductive electrode are output to a processing apparatus. [0023] The tube coating in method 400 may cause the endotracheal tube to have a color tint, and the tube coating may have a transmittance of about 74-93%. The tube coating may be formed from spraying the homogeneous solution in an aerosol form onto the endotracheal tube. The tube coating may be formed from a PVC solute dissolved in a mixture of solvents to form the homogeneous solution. The mixture of solvents may include cyclohexanone, tetrahydrofuran (THF), acetone, and an ink thinner. The homogeneous solution may include a food grade colorant.

[0024] Yet another embodiment is directed to a method of applying an electrode to an endotracheal tube. Figure 5 is a flow diagram illustrating a method 500 of applying an electrode to an endotracheal tube according to one embodiment. At 502 in method 500, a PVC solute is dissolved in a mixture of solvents to form a homogeneous solution. At 504, the homogeneous solution is sprayed in an aerosol form on an outer surface of the endotracheal tube to form a tube coating. At 506, a conductive electrode is printed on the tube coating.

[0025] The method 500 may further include adding a food grade colorant to the homogeneous solution before the spraying of the homogeneous solution. The method 500 may further include masking at least one region of the endotracheal tube before the spraying of the homogeneous solution to prevent formation of the tube coating in the at least one masked region. The method 500 may further include stirring the PVC solute and the mixture of solvents with a magnetic stirrer. The method 500 may further include rotating the endotracheal tube during the spraying of the homogeneous solution.

[0026] Although the present disclosure has been described with reference to

preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present disclosure.