Disposable LMA

Details Disposable LMA Disposable LMA

2000-04-07

2004-03-16

Lo, Weilun (Department: 3761)

Surgery

Respiratory method or device

Respiratory gas supply means enters mouth or tracheotomy...

C128S207150

Reexamination Certificate

active

06705318

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a laryngeal mask airway device. More specifically, the present invention relates to reduced cost laryngeal masks, improved geometric configurations for laryngeal masks, and to methods of inexpensively fabricating such masks.
The laryngeal mask airway device (LMA) is a well known device that is useful for establishing airways in unconscious patients. LMAs have been in use for about twelve years and offer an alternative to the older, even better known, endotracheal tube. For at least seventy years, endotracheal tubes comprising a long slender tube with an inflatable balloon disposed at the tube's distal end have been used for establishing airways in unconscious patients. In operation, the endotracheal tube's distal end is inserted through the mouth of the patient, past the patient's laryngeal inlet (or glottic opening), and into the patient's trachea. Once so positioned, the balloon is inflated so as to form a seal with the interior lining of the trachea. After this seal is established, positive pressure may be applied to the tube's proximal end to ventilate the patient's lungs. Also, the seal between the balloon and the inner lining of the trachea protects the lungs from aspiration (e.g., the seal prevents material regurgitated from the stomach from being aspirated into the patient's lungs).
Although they have been enormously successful, endotracheal tubes suffer from several major disadvantages. The principal disadvantage of the endotracheal tube relates to the difficulty of properly inserting the tube. Inserting an endotracheal tube into a patient is a procedure that requires a high degree of skill. Also, even for skilled practitioners, insertion of an endotracheal tube is sometimes difficult or not possible. In many instances, the difficulty of inserting endotracheal tubes has tragically led to the death of a patient because it was not possible to establish an airway in the patient with sufficient rapidity.
In addition to this principal disadvantage, there are also other disadvantages associated with endotracheal tubes. For example, intubation with an endotracheal tube often causes patients to suffer from severe “sore throats”. The “sore throat” is principally caused by friction between the tube and the notch between the patient's arytenoid cartilages. Another disadvantage is that patients can not cough effectively while intubated with an endotracheal tube. Yet another problem with endotracheal tubes relates to the manner in which they are inserted. Inserting an endotracheal tube normally requires manipulations of the patient's head and neck and further requires the patient's jaw to be forcibly opened widely. These necessary manipulations make it difficult, or undesirable, to insert an endotracheal tube into a patient who may be suffering from a neck injury. Still another disadvantage is that endotracheal tubes provide an airway that is relatively small or narrow. The size of the airway must be relatively narrow because the distal end of the tube must be sufficiently small to fit into the trachea.
In contrast to the endotracheal tube, it is relatively easy to insert an LMA into a patient and thereby establish an airway. Also, the LMA is a “forgiving” device in that even if it is inserted improperly, it still tends to establish an airway. Accordingly, the LMA is often thought of as a “life saving” device. Also, the LMA may be inserted with only relatively minor manipulations of the patient's head, neck, and jaw. Further, the LMA provides for ventilation of the patient's lungs without requiring contact with the sensitive inner lining of the trachea and the size of the airway established with an LMA is typically significantly larger than the size of the airway established with an endotracheal tube. Also, the LMA does not interfere with coughing to the same extent as endotracheal tubes. Largely due to these advantages, the LMA has enjoyed increasing popularity over the last twelve years.
FIG. 1
shows a perspective view of a prior art LMA
100
and
FIG. 2
illustrates an LMA
100
that has been inserted into a patient. LMAs such as LMA
100
are described for example in U.S. Pat. No. 4,509,514. LMA
100
includes a flexible cylindrical tube
110
and a mask portion
130
. Tube
110
extends from a proximal end
112
to a distal end
114
and mask portion
130
is coupled to the tube's distal end
114
. Mask portion
130
includes a proximal end
132
and a generally elliptical inflatable cuff
134
. Mask portion
130
also defines a central passageway extending from proximal end
132
to an open end
136
of cuff
134
. The distal end
114
of tube
110
is telescopically fit into the proximal end
132
of mask portion
130
, and LMA
100
provides a continuous, sealed, airway extending from proximal end
112
of tube
110
to the open end
136
of cuff
134
. LMA
100
also includes an inflation tube
138
for selectively inflating or deflating cuff
134
.
In operation, the cuff
134
is deflated, and then the mask portion is inserted through the patient's mouth into the patient's pharynx. The mask portion is preferably positioned so that a distal end
140
of cuff
134
rests against the patient's normally closed esophagus and so that the open end
136
of the cuff
134
is aligned with the entryway of the patient's trachea (i.e., the patient's glottic opening). After the mask portion is so positioned, the cuff is inflated thereby forming a seal around the patient's glottic opening and this establishes a sealed airway extending from the proximal end
112
of the tube
110
to the patient's trachea.
For convenience of exposition, the term “fully inserted configuration” shall be used herein to refer to an LMA that has been inserted into a patient and has the following characteristics: (1) the mask portion is disposed around the patient's glottic opening; (2) the cuff is inflated forming a seal around the patient's glottic opening; and (3) the airway tube extends from a proximal end located outside the patient's mouth to a distal end that is coupled to the mask portion, the tube extending through the patient's mouth and the patient's natural upper airway so that the LMA provides a sealed airway extending from the tube's proximal end to the patient's lungs.
FIG. 2
shows an LMA in the fully inserted configuration.
When LMA
100
is in the fully inserted configuration, LMA
100
advantageously does not contact the interior lining of the trachea. Rather, the seal is established by contact between the tissues surrounding the patient's laryngeal inlet and the inflatable cuff
134
. Unlike the delicate interior lining of the trachea, the tissues at the laryngeal inlet are accustomed to contact with foreign matter. For example, during the act of swallowing food, the food is normally squeezed against these tissues on its way to the esophagus. These tissues are accordingly less sensitive and less susceptible to being damaged by contact with the inflatable cuff.
FIG. 3
shows a sectional side view of the mask portion
230
of another prior art LMA. The illustrated mask portion
230
, which is described more fully in U.S. Pat. No. 5,355,879, includes an inflatable cuff
234
and a backplate
250
. Backplate
250
defines a proximal end
232
for receiving, or coupling to, a cylindrical airway tube (not shown). Mask portion
230
defines a sealed passageway, or airway, that extends from proximal end
232
through to the open end
236
of cuff
234
. This mask portion
230
also includes an inflatable back cushion that, when inflated, expands to the contour illustrated by phantom outline
252
. As shown in
FIG. 3
, the cross sections of prior art cuffs are generally circular. The thickness T
1
of the material used to form the cuff (i.e., the thickness of the cuff wall) is normally about 0.7-0.8 millimeters.
U.S. Pat. No. 5,303,697 describes an example of another type of prior art LMA that i

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