certain features of the device described and shown herein are enlarged in the figures for clarity and may be smaller and thinner then depicted in the figures . in addition , other components , which may or may not be transparent , are shown as transparent so that the locations of the underlying features are readily visible . with reference to fig1 - 3 , a laryngeal electromyography tube 10 for use in prolonged laryngeal electromyography monitoring is shown . the laryngeal electromyography tube 10 comprises an endotracheal tube 12 upon which conductive electrode plates 14 are imprinted on the linear body of the tube 12 from a point adjacent to the endotracheal tube balloon 15 , shown as a transparent material , at the distal end 16 of the tube 12 . the length of the electrode plate 14 is chosen so as to be appropriate for clinical use and electrical signal capture . extending away from the plates 14 , toward the proximal end 18 of the laryngeal electromyography tube 10 is a conductive trace 20 which terminates on a conductive pad 22 for attachment of a lead wire 24 . the lead wire 24 is of a length suitable to allow the laryngeal electromyography tube 10 to be attached to externally located electro - physiologic devices ( not shown ) such that the user may capture and evaluate the signals from the vocal cord received by the plates 14 . a typical endotracheal tube has a curved shape , such as an arc as shown in fig1 - 3 which typically is bent into an s - shape to match the anatomy of the throat . in fig1 - 3 the printed electrodes are shown on the outer curved surface for receiving electrical signals generated from nerves and muscles in the rear of the trachea . a second embodiment of the laryngeal electromyography tube 40 shown in fig4 and 5 has the electrodes placed on the concave ( inner surface of the curve ) for picking up signals generated from the vocal cord located on the front surface of the trachea . fig6 shows a third embodiment of a laryngeal electromyography tube 50 incorporating features of the invention . this embodiment incorporates the electrode plate 14 placement of fig1 - 3 with the conductive trace 20 running along the lower surface of the endotracheal tube , the portion of the trace 20 connecting to the plate 14 curving around the surface of the endotracheal tube so that the electrode plate 14 faces rearward to contact the vocal cords and the conductive trace 20 is on the lower surface of the tube as it passes through the mouth ( i . e ., facing the tongue ). one skilled in the art will recognize that other electrode placements may be desired and it may in fact be desirable to have electrodes extending further around the circumference or even around the full 360 ° circumference of the tracheal tube . additional imprinting 26 for informational purposes is applied using nonconductive paint or printing ink is also seen on the body of the invention . an insulating covering 28 , shown as a transparent material , is applied over the traces to protect against electrical shorting . fig7 and 8 show a still further embodiment 60 which includes a single wide electrode 62 in contact with the vocal cords and a second electrode 64 which rests against the tongue as best shown in fig8 . in fig7 , a second conductive pad 22 connected to the trace 66 is not seen as it is on the backside of the endotracheal tube as viewed in fig7 . a suitable conductive composition , referred to as an ink or paint , for forming the plates 14 and the traces 20 comprises a mixture of conductive materials , preferably metallic particles or metallic salts or oxides dissolved or suspended in a liquid carrier . suitable conductive particles include , but are not limited to , finely divided particles or flakes of silver , silver salts such as silver chloride , silver oxide , gold , copper , copper chloride , platinum , carbon or graphite . the conductive materials are provided in the form of pellets , flakes , and nanoparticles . silver is preferred because it is highly conductive ( it has a resistivity of 1 . 62 × 10 − 8 ωm ), is oxidatively stable and has the added advantage that its oxide is electrically conductive . copper has a similar resistivity but its oxide acts as an insulator . the conductive materials are dissolved or suspended in a carrier which can be readily evaporated , leaving the conductive particles adhered to the surfaced of the endotracheal tube and in contact with adjacent particles to create a continuous conductive path from the electrode plate 14 along the length of the endotracheal tube to the conductive pad 22 and then to the lead wires 24 . a typical ink comprises a mixture of the conductive material , which may include one or more different materials such as silver in combination with silver chloride , in a liquid carrier , and may also include a binding agent or adhesion promoter . a typical ink for use on a polyvinyl chloride ( pvc ) endotracheal tube comprises 20 - 40 % of a liquid carrier and 60 - 80 % of a conductive material blend . for example a particular embodiment for use on pvc comprises 30 % of a liquid carrier , such as dipropylene glycol methyl ether , 60 % silver in the form of 50 % silver flakes and 10 % silver chloride , and a resin binder such as a modified polyester resin . once the liquid carrier is removed , the printed electrode comprises about 85 % conductive silver material ( silver and silver chloride ), the balance being the resin binder . numerous suitable conductive inks are available from creative materials of tyngsboro , mass . for use on a silicone endotracheal tube a preferred carrier liquid is xylene . the ink typically has a viscosity in excess of 10 , 000 centipoises , preferably about 12 , 000 - 16 , 000 cps . one skilled in the art will recognize that numerous different carriers can be employed , preferably a liquid that does not attack or dissolve the polymeric material comprising the endotracheal tube and is readily evaporated . for example , other suitable liquid carriers include water , methanol , ethanol , isopropanol , 1 - methoxypropanol , butanol , ethylhexyl alcohol , terpineol , ethylene glycol , glycerine , ethyl acetate , butyl acetate , methoxypropyl acetate , carbitol acetate , ethylcarbitol acetate , methylcellosolve , butylcellosolve , diethyl ether , tetrahydrofuran , dioxane , methyl ethyl ketone , acetone , dimethylformamide , 1 - methyl - 2 - pyrrolidone , hexane , heptane , dodecane , paraffin oil , mineral spirit , benzene , toluene , xylene , chloroform , methylene chloride , carbon tetrachloride , acetonitrile and dimethylsulfoxide . the viscosity should also be such that the ink once applied does not flow on the surface of the tube so that the dimensions of the printed or painted electrode can be held with design parameters as to with ands thickness . to apply the ink to the endotracheal tube the tube can first be wiped with a solvent to remove any oils or foreign materials on the surface . care must be taken to select a cleaning solvent that is compatible with the polymeric material comprising the endotracheal tube and does not affect the surface of the tube . however , wiping the surface may not be necessary . in a first embodiment the conductive ink is applied using a brush , preferably in an automated manner to assure reproducibility . however , other techniques can be utilized such as spraying or using a roller type applicator or other typical printing techniques . in a preferred embodiment the printed surface is subjected to an elevated temperature ( 35 ° c .- 140 ° c . ), preferably 100 ° c .- 140 ° c . for several minutes to quickly evaporate the liquid carrier followed by 12 - 24 hours exposure in clean environment at ambient temperature . the resultant device is an endotracheal tube with an electrode structure toward the distal end thereof and traces from the electrode structure to the proximal end permanently printed on the outer surface thereof , the traces being electrically insulated . the printed electrode and traces are about 0 . 001 inches ( 25 microns ) in thickness so that the diameter of the endotracheal tube is substantially unchanged and there are no extraneous intervening materials , such as is present when a stick - on electrode is used , which can lift up or present sharp edges . a pvc endotracheal tube incorporating an electrode structure painted on the surface in the manner described above using the silver / silver chloride ink described above has been used in patients and provides consistent stimulation delivery ( the average minimum current required for stimulation of the rln is about 0 . 50 ma ) and a measurably and consistent output comparable to current electrodes adhesively secured on endotracheal tubes , such as the dragonfly ® stick - on laryngeal electrode supplied by neurovision medical , inc . such a composition can be applied by various methods including but not limited to painting , screen printing , transfer printing , gravure , flexographic or offset printing , as well as inkjet or electrostatic printing methods . the conductive solutions preferably use rapidly evaporating solvents which may be provided with high concentrations of the conductive component and can in fact be provided as a solvent free composition . as an alternative , a polymer doped with conductive additives can be used . in a still further embodiment electrically conductive polymers can be used . based on the teachings herein one skilled in the art will recognize that other conductive solutions or compositions can be utilized . preferred materials for construction of the endotracheal tube are pvc or a silicone polymer , such as silastic ®. however , based on the teachings herein one skilled in the art will recognize that numerous alternative materials may be used to construct the endotracheal tube 12 . the non - conductive , insulating covering 28 is chosen to be compatible with the tube 12 material to minimize or eliminate the likelihood of delamination . for example , on a pvc endotracheal tube a pvc insulating covering 28 is preferred . for a silicone endotracheal tube , a silicone insulating covering 28 is preferred . while the device described herein is an endotracheal tube , one skilled in the art will also recognize that other medical devices , such as catheters can be prepared in the same manner to have electrodes on the surface thereof . the endotracheal tube with imprinted electrode surfaces allows safe , long term intubation and clinical monitoring of human laryngeal electromyographic signals . prior and currently available devices include structures on the surface of the tube which are raised and can have sharp edges and which can cause injury to the tissue of the throat , larynx and vocal cords . for these reasons , the manufacturers of all currently available laryngeal surface electrodes do not recommend continuous laryngeal electrode placement for monitoring purposes in excess of eight hours . the surgeon and anesthesiologist are therefore required to remove the dedicated endotracheal tube with attached electrode and reintubate the patient with a standard , non - electrode endotracheal tube prior to moving the patient to the recovery room or icu for prolonged respiratory support . this entails the risk of a separate , second airway manipulation and deprives the physician of valuable information which is provided by prolonged and continuous laryngeal monitoring . since the currently described device with electrical paths applied directly to the surface of the endotracheal tube are smooth , these hazards are eliminated . the described device can be placed prior to or at the time of the surgical procedure , and it can remain in position in the patient after the procedure ( i . e ., in the recovery room , icu and subsequent prolonged respiratory support ) with significantly reduced risks of injury to the patient . intubations in excess of 8 hours and in fact for 24 - 48 hours ( long term intubation ) are therefore now possible . further , printing the electrode on the surface provides for optimization of the configuration of the electrode plates on the body of the endotracheal tube without introducing stiff attachments or physical additions . as a result no physical stress is placed on the tube that could inhibit easy placement of the tube in the trachea of a human patient . while specific embodiments are disclosed herein , it is understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various forms . specific structural and functional details described herein are not to be interpreted as limiting , but merely exemplary and are a basis for teaching one skilled in the art to practice the invention claimed herein below .
laryngeal surface electrodes are devices designed to hold a conductive surface against the vocal cords in order to pick up small electrical signals from the muscle known as electromyographic signals . several embodiments of a laryngeal electromyography tube include a conductive electrode surface that is painted , screen printed or otherwise applied directly onto the body of an endotracheal tube , such that the final device has no raised surfaces which can injure the vocal cords . these endotracheal tube with integral laryngeal surface electrodes can be safely used placed for prolonged , continuous monitoring during surgery , after surgery and during intensive care treatment intubation without a need to remove and replace the tube at these various stages of treatment . in one embodiment , one electrode contacts the vocal cords and a second electrode contacts the tongue .