Perilaryngeal oral airway

Details Perilaryngeal oral airway Perilaryngeal oral airway

2002-05-14

2004-05-04

Lewis, Aaron J. (Department: 3761)

Surgery

Respiratory method or device

Means placed in body opening to facilitate insertion of...

C128S207140, C128S207150

Reexamination Certificate

active

06729325

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to a class of medical devices commonly referred to as oral airways and supraglottic airways which are inserted through a patient's mouth and into the patient's pharynx while the patient is undergoing general anesthesia or is undergoing respiratory treatment such as is carried out with cardiopulmonary resuscitation. More specifically, the present invention is directed to a perilaryngeal oral airway and perilaryngeal supraglottic airway which is capable of acting as an endotracheal tube guide and which seats deep in a patient's hypopharynx to prevent the soft tissue of the glottis and epiglottis from obstructing the airway.
BACKGROUND ART
Oral airways were introduced into the practice of anesthesia and cardiopulmonary resuscitation several decades ago for two basic purposes. First, they prevent the patient's biting down on and occlusion of a previously placed oral endotracheal tube. Second, and most important, oral airways help to provide a patent airway that allows positive pressure ventilation to be carried out by the practitioner. More recently, some oral airways have been developed to facilitate blind (not visually directed) placement of an endotracheal tube.
For most patients, mask ventilation is carried out successfully by insertion of an oral airway and by a variety of physical adjustments, such as extension of the patient's neck and elevation of the patient's jaw. However, in some patients, no matter what physical adjustments are made or the particular oral airway which is inserted, mask ventilation cannot be successfully achieved. Such cases are literally life-threatening as hypoxemia and death can quickly ensue if the patient's blood is deprived of oxygen due to a lack of ventilation.
When mask ventilation (even with the use of an oral airway) cannot be carried out, there are multiple mechanisms responsible. Most significantly, soft tissue structures in the hypopharynx (the area between where conventional oral airways end and the glottis opens into the trachea) collapse inwardly and obstruct airflow. This collapse occurs from both an antero-posterior direction, as well as from the sides of the hypopharynx. Unfortunately, all oral airways which have been introduced into practice to date end bluntly well above the epiglottis (the cartilaginous structure just above the glottis or laryngeal opening) and glottis and thus place patients at risk for significant airway obstruction. Another mechanism of airway obstruction which occurs while using oral airways is the patient having large lips covering the outside opening of the oral airway with subsequent inadequate airflow through the nasal passages (due to the solid posterior wall of the airway limiting passage of air into the airway at the level of the nasopharynx).
Additionally, most known oral airways are comprised of a hard plastic material throughout their length with no variation in softness between one end of the oral airway and the opposite end. As a result, the distal end (i.e., the end which first enters the mouth and passes down into the pharynx of the patient) often bruises or otherwise damages soft mucosal surfaces of the patient during insertion or once the oral airway has been seated in place.
Representative prior art airways include Baildon, U.S. Pat. No. 4,919,126, which discloses an oral airway formed of plastic which includes an air passageway extending longitudinally through the airway. The distal end has a projecting solid anterior portion which serves as an “epiglottis elevator.” As such, the oral airway is blunt-shaped in configuration and ends well above the glottis. For this reason, the Baildon oral airway suffers from the problems discussed above in that it fails to provide any structure to prevent the collapse of soft tissue structures in the hypopharynx.
Berman, U.S. Pat. Nos. 4,054,135 and 4,067,331, relate to an intubating pharyngeal airway having a side access for passage of an endotracheal tube. The airway includes a blunt end on the anteriorly extending wall which is designed to fit into the vallecula (area between the epiglottis and tongue). Accordingly, the devices disclosed in both of Berman's patents are similar to the device of Baildon in that they can detrimentally allow soft tissue structures to invaginate inward and thereby occlude the passage of air.
Moses, U.S. Pat. No. 3,908,665, discloses an oro-pharyngeal airway wherein the outer diameter of the body portion progressively increases from the end closest to the mouth to the opposite end thereof so as to relieve any obstruction to the flow of air by the base of the tongue falling back on the posterior pharyngeal wall. However, the airway of Moses likewise suffers from the problems discussed in detail above in that the blunt-shaped end terminates well above the glottis, thereby allowing possible soft tissue obstruction to occur.
Augustine, U.S. Pat. No. 5,203,320, discloses a tracheal intubation guide which similarly seats above the glottis. Moreover, the device of Augustine functions as a guide for placing an endotracheal tube in a “blind” manner and is neither designed for nor could it possibly function to allow mask ventilation to be carried out.
In addition, for some patients it is important to use an airway device which provides a seal within the patient's airway (trachea, oro- or hypopharynx) in order to better allow positive pressure ventilation to be accomplished. Traditionally, this has been achieved by using an endotracheal tube passed between a patient's vocal cords. In an effort to avoid the deleterious effects of tracheal intubation (e.g., bronchospasm, dental injury and cardiovascular stimulation), the laryngeal mask airway (“LMA”) has been introduced into clinical practice. The LMA is illustrated and described in Brain, U.S. Pat. No. 4,509,514. While providing a seal with which to administer positive pressure ventilation, there are several potential problems when using an LMA. First, the device is easily malpositioned so that ventilation is not possible, for example, by virtue of the epiglottis bending back over the glottis and thereby obstructing air flow. Second, by directly covering the glottic aperture, trauma to the glottic structures (arrhytenoid cartilages, vocal cords) can occur. In addition, the cost of this product (over $200) becomes a factor when limitations to reuse occur due to physical damage of the device or accidental loss. Third, as a reusable product, the hazard of cross-contamination from one patient to another cannot be completely eliminated.
Because of the above-limitations of the LMA, a cuffed oro-pharyngeal airway has been introduced into clinical practice. Greenberg, U.S. Pat. No. 5,443,063, describes such a device as an oro-pharyngeal cuff placed over a conventional oral airway. However, this device has several significant limitations which prevent it from functioning adequately. First, the airway suffers from the problems of those previously discussed in that it ends well above the glottis, thereby allowing soft tissue obstruction to impair the flow of oxygen to the lungs. Second, with the cuff placed so far proximally in the oro-pharynx, the device tends to push itself out of the patient's mouth, thereby requiring that the device be secured in place by means of a strap placed around the patient's head. Finally, the cuff is positioned so far proximally in the patient's airway that it often allows leakage of oxygen and anesthetic gases around the cuff, thereby preventing the formation of an air-tight seal. This, of course, makes positive pressure ventilation impossible in those patients.
Several oral airways, including those described in the patents to Berman and Augustine, have been introduced into clinical practice in an effort to provide a means to accomplish blind intubation of a patient's trachea with an endotracheal tube (or to facilitate fiberoptic intubation). These devices end well above the glottic opening and thus function poorly in terms of reliably directing

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