Abstract:
Concepts presented herein include an apparatus for monitoring EMG signals of a patient&#39;s laryngeal muscles. The apparatus includes an endobronchial tube having an exterior surface and two lumens for providing ventilation. Conductive ink electrodes are formed on the exterior surface of the endobronchial tube. The conductive ink electrodes are configured to receive the EMG signals from the laryngeal muscles when the endotracheal tube is placed in a trachea of the patient. At least one conductor is coupled to the conductive ink electrodes and is configured to carry the EMG signals received by the conductive ink electrodes to a processing apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/688,818, filed Nov. 29, 2012, now U.S. Pat. No. 9,060,744, the specification of which is incorporated by reference herein. 
    
    
     BACKGROUND 
     Endobronchial tubes (also known as dual-lumen endotracheal tubes) provide an open airway for patient ventilation during surgery. In particular, endobronchial tubes are used during surgical procedures to provide ventilation to individual lungs separately. Current endobronchial tubes include a first, tracheal lumen and a second, bronchial lumen. Each lumen includes an associated inflatable cuff, the cuff associated with the tracheal lumen being positioned within the trachea and the cuff associated with the bronchial lumen being positioned within one of the bronchus. 
     SUMMARY 
     Concepts presented herein include an apparatus for monitoring EMG signals of a patient&#39;s laryngeal muscles. The apparatus includes an endobronchial tube having an exterior surface and two lumens for providing ventilation. Conductive ink electrodes are formed on the exterior surface of the endobronchial tube. The conductive ink electrodes are configured to receive the EMG signals from the laryngeal muscles when the endotracheal tube is placed in a trachea of the patient. At least one conductor is coupled to the conductive ink electrodes and is configured to carry the EMG signals received by the conductive ink electrodes to a processing apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an EMG endobronchial tube. 
         FIGS. 2A and 2B  are different side views of an endobronchial tube. 
         FIG. 2C  is a sectional view of the endobronchial tube illustrated in  FIG. 2A . 
         FIG. 3  is a partial side view of an endobronchial tube having an electrode cuff. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an EMG endobronchial tube  100  made from extruded polymer. Endobronchial tube  100  includes solid wires  102 , a bronchial fitting  104 , a tracheal fitting  106 , a y-connector  108 , a bronchial cuff inflating conduit  110 , a tracheal cuff inflating conduit  112 , extruded polymer tube  114 , electrodes  116 , bronchial cuff  120  and tracheal cuff  122 . Solid wires  102  are connected to electrodes  116  at an interconnection  124 . Tube  114  transports gases to and from the lungs. In particular, tube  114  defines a first, bronchial lumen  126  extending from bronchial fitting  104  to an opening  128  distal the bronchial cuff  120  and a second, tracheal lumen  130  extending from tracheal fitting  106  to an opening  132  distal the tracheal cuff  122 . The Y-connector  108  fluidly couples the bronchial fitting  104  and tracheal fitting  106  to bronchial lumen  126  and tracheal lumen  130 , respectively. 
     Fittings  104  and  106  are configured to be connected to a respirating machine (not shown) for injecting air into the lungs and withdrawing air from the lungs. Cuff inflating conduits  110  and  112  are configured to be connected to a source of compressed air (not shown) for inflating cuffs  120  and  122 . Cuff inflating conduit  110  communicates with a lumen located in the wall of tube  114 , and the lumen communicates with bronchial cuff  120 . Likewise, tracheal cuff inflating conduit  112  communicates within a lumen located in the wall of tube  114 , and the lumen communicates with tracheal cuff  122 . During use, one of the fittings (e.g., bronchial fitting  104 ) is configured to inject air into one lung while the other fitting (e.g., tracheal fitting  106 ) is configured to injected air into the other lung. For example, cuff  120  can be positioned into the left bronchus and cuff  122  positioned into the trachea. In this case, opening  126  is positioned to direct air into the left lung from bronchial fitting  104  while opening  132  is positioned to direct air into the right lung from tracheal fitting  106 . Selectively, air can be provided to only one of the fittings  104 ,  106  so as to provide air to only a single lung and collapsing the other lung. In such a case, a surgeon can operate proximate the collapsed lung or on the collapsed lung. After endobronchial tube  100  is inserted into the trachea of a patient, electrodes  116  sense EMG signals, which are output to an EMG processing machine, such as nerve integrity monitor (NIM) device  140 , via solid wires  102 . Die cut tape may be used to tape tube  114  to a patient&#39;s mouth to secure the tube and keep it appropriately positioned. 
     In one embodiment, the NIM  140  is configured to determine when the electrodes  116  are in contact with the vocal folds, and is configured to provide an alert to the surgeon when such contact is lost. In one embodiment, the NIM  140  is also configured to determine whether the electrodes  116  are in contact with muscle or tissue based on the received signals 
     In one embodiment, tube  114  is a braided tube that is more flexible than conventional solid polymer tubes, and that reduces kinking. Tube  114  according to one embodiment is formed from a braided polymer or nitinol within a thin-walled tube, and reduces or eliminates rotation of the tube at the vocal folds, while allowing a proximal portion of the tube to rotate. 
       FIG. 2A  shows a first side view (posterior side) of endobronchial tube  114  with four electrodes  116 .  FIG. 2B  shows a second side view (rotated 90 degrees from the view shown in  FIG. 2A ) of the endobronchial tube  114  shown in  FIG. 2A .  FIG. 2C  is a diagram illustrating a cross-sectional view of the endobronchial tube  114  shown in  FIGS. 2A and 2B . 
     Electrodes  116  include four electrodes  116 A- 116 D, which are formed around a circumference of the tube  114  and extend in a longitudinal direction of the tube  114 . Electrodes  116 A and  116 B are positioned entirely on the posterior side of the tube  114  and are also referred to herein as posterior electrodes  116 A and  116 B. Electrodes  116 C and  116 D are positioned entirely on the anterior side of the tube  114  and are also referred to as anterior electrodes  116 C and  116 D. The anterior side of the tube  114  is the bottom half of the tube  114  shown in  FIG. 2C , and the posterior side of the tube  114  is the top half of the tube  114  shown in  FIG. 2C . Each of the electrodes  116 A- 116 D is coupled to a respective trace  150 A- 150 D (trace  150 D is not visible in the Figures). Traces  150 A- 150 D are positioned in a protected (masked) region  152  of tube  114 . Posterior electrodes  116 A and  116 B are positioned in an exposed (unmasked) region  154  of tube  114 . Anterior electrodes  116 C and  116 D are positioned in an exposed (unmasked) region  156  of tube  114 . 
     In one embodiment, each of the electrodes  116 A- 116 D has a length of about one inch, and extends laterally around a circumference of the tube for a distance corresponding to an angle  160  of about 60 degrees (i.e., each of the electrodes  116 A- 116 D has a width of about 16.67 percent of the total circumference of the tube). The electrodes are laterally spaced apart around the circumference of the tube by a distance corresponding to an angle  160  of about 30 degrees (i.e., the lateral spacing between each of the electrodes  116 A- 116 D is about 8.333 percent of the total circumference of the tube). The posterior electrodes  116 A and  116 B are longitudinally offset or displaced from the anterior electrodes  116 C and  116 D. The posterior electrodes  116 A and  116 B are positioned closer to the distal end (right side in  FIGS. 2A and 2B ) of the tube  114  than the anterior electrodes  116 C and  116 D, and the anterior electrodes  116 C and  116 D are positioned closer to the proximal end (left side in  FIGS. 2A and 2B ) of the tube  114  than the posterior electrodes  116 A and  116 B. 
     Tube  114  includes an overlap region  166  where a proximal portion of the posterior electrodes  116 A and  116 B longitudinally overlap with a distal portion of the anterior electrodes  116 C and  116 D. The electrodes  116  do not physically overlap each other since they are laterally offset from each other. In one embodiment, the overlap region  166  is about 0.1 inches long, and the overall length from a proximal end of the anterior electrodes  116 C and  116 D to a distal end of the posterior electrodes  116 A and  116 B is about 1.9 inches. In another embodiment, the overlap region  166  is about 0.2 inches long, and the overall length from a proximal end of the anterior electrodes  116 C and  116 D to a distal end of the posterior electrodes  116 A and  116 B is about 1.8 inches. Tube  114  is configured to be positioned such that the vocal folds of a patient are positioned in the overlap region  166 . Thus, the configuration of the electrodes  116  above the vocal folds is different than the configuration below the vocal folds. The posterior electrodes  116 A and  116 B are configured to be positioned primarily below the vocal folds, and the anterior electrodes  116 C and  116 D are configured to be positioned primarily above the vocal folds. In one embodiment, electrodes  116 A and  116 C are used for a first EMG channel, and electrodes  116 B and  116 D are used for a second EMG channel. 
     In an alternate embodiment, all four surface printed electrodes,  116 A,  116 B,  116 C and  116 D, are equal in length. This will allow the finish product to be placed with little concerns of rotational alignment. 
     As illustrated in  FIG. 2C , conduits  110  and  112  are formed in a thickness of the tube  114  to carry compressed air to bronchial cuff  120  and tracheal cuff  122 , respectively. Additionally, inside tube  114  are formed bronchial lumen  126  and tracheal lumen  130 . During use, one of the lumens  126  and  130  can be used to inject gases into a particular lung while the other lumen is sealed from injecting gases into the opposite lung. 
     With reference to  FIG. 3 , another embodiment includes an electrode cuff  170  positioned proximal the tracheal cuff  122 . In the embodiment of  FIG. 3 , cuff  122  is of a different shape than that illustrated in  FIGS. 1-2C . Other shapes for the cuffs  122  and  170  can be utilized. Electrodes  116  are applied directly to the electrode cuff  170  and are similar to that discussed above. Cuffs  122  and  170  are sized so as to both provide suitable sealing between the trachea and cuff  122  yet provide suitable compliance of electrode cuff  170  in contact with the vocal folds of a patient when inflated by pressurized fluid provided within inflating conduit  110 . Upon inflation, the tracheal cuff  122  has a larger diameter D 1  than a diameter D 2  of electrode cuff  170 . In some embodiments, the diameter D 2  is selected to be approximately half the diameter D 1 . In one example, D 1  is about 20 millimeters, whereas D 2  is about 9 millimeters. In yet a further embodiment, D 1  is approximately 27 millimeters, whereas D 2  is approximately 14 millimeters. Moreover, a length L 1  of the cuff  170  is selected to be greater than a length L 2  for cuff  122 . In one embodiment, the L 1  is approximately 1.875 inches. In another embodiment, L 1  is in a range from approximately 1.5 inches to 2.5 inches. In a further embodiment, a ratio of D 1 :L 1  is selected to be in a range from approximately 15:100 to 30:100. 
     Furthermore, a compliance for cuff  170  is selected so as to prevent trauma due to cuff  170  contacting the vocal folds of the patient. In one embodiment, the cuff  170  is formed of a semi-compliant balloon. The semi-compliant balloon will increase in diameter about 10 to 20 percent from a nominal pressure to a rated burst pressure for the balloon. In a further embodiment, cuff  170  is formed of a compliant balloon such that the balloon will increase in diameter from 20 to 200 percent from a nominal pressure to a rated burst pressure of the balloon. In a further embodiment, the cuff  170  is formed of a compliant material that has a greater compliance than a material selected for cuff  122 . In one embodiment, cuff  122  has a compliance defined as increasing in diameter about 20 to 200 percent from a nominal pressure to a rated burst pressure for the cuff  122 . 
     Inflating conduit  110  extends along the length of tube  114  to electrode cuff  170  and continues in extension to the tracheal cuff  122 . Due to relative compliance of the cuffs  122  and  170 , cuff  122  is configured to fluidly seal the trachea of a patient when positioned, whereas electrode cuff  170  inflates to contact the vocal folds of the patient so as to prevent trauma from occurring due to contact between the cuff  170  and the vocal folds. Furthermore, by selecting diameters D 1  and D 2  of cuffs  122  and  170 , tension exerted on an exterior surface of each cuff is adjusted. In one embodiment, thickness and diameter for cuffs  122  and  170  are selected such that cuff  122  will absorb pressure and reduce pressure on cuff  170 . In this configuration, cuff  170  can conform to a shape of vocal folds and ensure sufficient electrical contact between the electrodes  112  and the vocal folds without causing irritation by exerting too much pressure on the vocal folds. 
     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.