Indotracheal tube

Details Indotracheal tube Indotracheal tube

1998-06-22

2001-07-24

Lacyk, John P. (Department: 3736)

Surgery

Diagnostic testing

Structure of body-contacting electrode or electrode inserted...

C600S393000

Reexamination Certificate

active

06266548

ABSTRACT:

The present invention relates to a double-balloon endotracheal tube, comprising a tube segment and at least two balloons which are arranged adjacent to one another and can be expanded independent of one another, of which the top one has atraumatic sensors for checking the motor laryngeal nerves assigned to it.
Damage to the recurrent laryngeal nerve (nervus laryngeus recurrens=NLR) is a serious complication in throat operations. Loss of function on both sides is a life-threatening emergency situation. Large numbers of statistics for over 12,000 struma resections showed a recurrent laryngeal nerve paresis rate of 1.2% and 5.2%, respectively, regardless of whether or not the nerve was presented (exposed) during the operation. Therefore there is essentially unanimity concerning the fact that the NLR should be exposed during thyroid operations, in order to preclude accidental injury. A variant course and the extremely small size of its structure frequently result in difficulties in identification of the nerve. This is particularly true with regard to large strumae, repeat operations, and tumor operations. Here the rate of injury of the NLR is as high as 20%. Damage to the superior laryngeal nerve (nervus laryngeus superior=NLS) is reported for up to 25% of all patients, even if the strumae are uncomplicated. In the majority of cases of postoperative function problems of the NLR, the surgeon is able to definitely preclude the possibility that the nerve has been cut through. Therefore the cause of the damage is primarily due to stretching or compression of the nerve, or its being knotted into the surgical suture. This results in the urgent need for continuous, intraoperative monitoring of the NLR, in order to recognize the threat of injury to the nerve during mobilization of the thyroid, in timely manner.
Many different attempts at intraoperative identification of the NLR and intraoperative monitoring of its function have already been undertaken. For example, Dale B. Smith and others, in the essay “A device for the intraoperative identification of the recurrent laryngeal nerve in piglets” (Otolaryngology—Head and Neck Surgery 1989, 100, p. 137-145), describe the double-balloon endotracheal tube mentioned initially. Here, the sensors assigned to the top balloon function hydraulically. The corresponding tube is introduced into the trachea to such an extent that the top balloon comes to rest in the region of the glottis. In this position, the tube is fixed in place in the trachea and sealed with regard to the latter, in that the bottom balloon is pumped up. Subsequently, the top balloon is expanded until it rests against the vocal cords. The NLR is electrically stimulated during the operation, which results in a corresponding muscle contraction of the glottis, with the prerequisite that the NLR is not damaged. This muscle contraction results in a pressure increase in the top balloon, which is indicated on the pressure gauge to which the latter is connected.
The decisive disadvantage of this known endotracheal tube is that using this tube, it is only possible to detect significant injury of the NLR which has already occurred, as demonstrated by gross changes in its function. However, impairment of individual axons of the nerve, which is attributable to external influences, cannot be detected. Likewise, slight and reversible traumas of the NLR, such as traction on the nerve and therefore the threat of damage that has not yet occurred, cannot be shown with the known endotracheal tube.
Since the NLR serves not only to close but also to open the vocal cords, traumas can remain undiscovered or even be incorrectly interpreted, if they do not result in a pressure increase but in constant pressure or even a pressure decrease.
The process cannot be used to detect the electrical inherent activities of the nerves which are triggered by mechanical contact and appear as so-called “spikes” in the EMG. Their duration is too short to be detected and quantified by the rough method of measuring pressure. Fundamentally, therefore, pressure measurement in the glottis does not solve the task to be solved, that of reliable intraoperative monitoring of the tracheal nerves.
Furthermore, various other methods and corresponding devices were described, which were intended for intraoperative presentation of the electrically stimulated NLR. D. J. Premachandra and others, in their essay “Intraoperative identification of the recurrent laryngeal nerve and demonstration of its function” (Laryngoscope 1990, 100, p. 95-96) describe the visualization of vocal cord mobility by means of a rigid endoscope. A. G. James and others, in their essay “A simple method for identifying and testing the recurrent laryngeal nerve” (Surgery Gynecology Obstetrics 1985, 161; p. 185-186), explained that the integrity of the NLR can be tested by palpation of the m. cricothyroideus. J. G. Spahn and others, in their essay “Identification of the motor laryngeal nerves—a new electrical stimulation technique” (Laryngoscope 1991, 91; p. 865-868), described that a fine needle placed in the fissure of the glottis performs visible movements during a movement of the glottis triggered by electrical stimulation of the NLR. A traumatic derivation process by means of a bipolar needle electrode was described by W. E. Davis in his essay “Recurrent laryngeal nerve localization using a microlaryngeal electrode” (Otolaryngology—Head and Neck Surgery, Vol. 87, p. 330 ff.). However, because of technical difficulties and/or traumatizing derivation procedures, none of these methods was able to come into general use until now. The last method mentioned additionally has the disadvantage that only individual motor units are capable of derivation; the method therefore provides no information about the integrity of the nerve as a whole. Derivation by means of needle or hook electrodes, whatever type they may be, cannot reliably solve the problem of intraoperative monitoring. No continuous monitoring process exists.
J. Lee Rea, finally, in his essay “Postcricoid Surface Laryngeal Electrode” (Ear, Nose and Throat Journal, Vol. 71, No. 6, p. 267 ff.), describes the atraumatic derivation of the NLR by means of an element provided with surface electrodes, which is intended to be inserted into the glottis. However, the device described here is practically useless for its intended purpose, because its use can result in damage to the surrounding tissue. Furthermore, the device cannot be placed in the intended location with sufficient certainty, and dislocation during its use is not definitely precluded.
Dislocation of the electrodes and the inaccuracy of the derivation in case of only small movements of the endotracheal tube are the main problems of a derivation system which was described by Andrew Goldstone (EP-0438863 A1). Here, two wires are affixed on the tube exactly parallel to the tube axis, which are intended to detect electrical activity of the vocal cords. However, reliable derivation is not possible because if the tube is moved or turned only slightly, contact with the vocal cords can be lost. The different status of opening of the vocal cords can also cause a problem with derivation. The contact pressure which is changed when this occurs can result in amplitude changes of the signal, while the signal derivation is maintained. Recognition of the threat of lesion of the NLR and of the NLS will therefore fundamentally not take place with this device. Continuous monitoring of the NLS and the NLR is not practicable with this device. Since a tube with a maximum thickness is always required in order to produce contact with the vocal cords, the risk of injury to the vocal cords increases dramatically, since the respiration tube with the surface wires running longitudinally on it must be forced through the vocal cords. It is possible that the vocal cords could be cut as a result. The device described by Goldstone can therefore not be used for the intended purpose.
The present invention is based on the task of creating a double-balloon endotracheal tube of the

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