U.S. patent number 3,794,036 [Application Number 05/277,316] was granted by the patent office on 1974-02-26 for pressure regulated inflatable cuff for an endotracheal or tracheostomy tube.
Invention is credited to Robert G. Carroll.
United States Patent |
3,794,036 |
Carroll |
February 26, 1974 |
PRESSURE REGULATED INFLATABLE CUFF FOR AN ENDOTRACHEAL OR
TRACHEOSTOMY TUBE
Abstract
An elastic cuff encircles a tracheostomy or endotracheal tube
near its distal end and has opposite ends fitting tightly against
the tube, with the proximal end of the cuff sealed to the tube. A
tubule with a distal end opening into the inside of the cuff
extends therefrom outwardly along the tube and has an outer end for
air under pressure for inflating the cuff. The distal end of the
cuff forms a check valve stretchable radially away from the tube by
excessive air pressure in the cuff if the air delivered thereto
through said tubule results in a pressure drop across the valve
exceeding a predetermined amount, whereupon the pressure drop will
be reduced to that predetermined amount.
Inventors: |
Carroll; Robert G. (Pittsburgh,
PA) |
Family
ID: |
23060326 |
Appl.
No.: |
05/277,316 |
Filed: |
August 2, 1972 |
Current U.S.
Class: |
128/207.15 |
Current CPC
Class: |
A61M
16/04 (20130101) |
Current International
Class: |
A61M
16/04 (20060101); A61m 025/00 () |
Field of
Search: |
;128/348,349B,349BV,351,202,208,344,246 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Rosenbaum; Charles F.
Attorney, Agent or Firm: Brown, Murray, Flick &
Peckham
Claims
I claim:
1. The combination with an endotracheal or tracheostomy tube having
distal and proximal ends, of an elastic cuff encircling the tube
near its distal end and having opposite ends fitting tightly
against the tube with the proximal end of the cuff sealed to the
tube, and a tubule extending from the cuff outwardly along said
tube and having a distal end communicating with the inside of the
cuff, the proximal end of the tubule having an inlet for air under
pressure for inflating the cuff, and the distal end of the cuff
forming a check valve stretchable radially away from the tube by
excessive air pressure in the cuff if the air delivered thereto
through said tubule results in the pressure drop across said valve
exceeding a predetermined amount, whereby said pressure drop will
be reduced to said predetermined amount.
2. The combination recited in claim 1, including means tacking said
distal end of the cuff to the tube to prevent it from sliding along
the tube.
3. The combination recited in claim 1, in which said distal end of
the cuff is in the form of a cylindrical band.
4. The combination recited in claim 1, in which said distal end of
the cuff is in the form of a cylindrical band secured at at least
one point to the tube to prevent it from sliding along the
tube.
5. The combination recited in claim 1, in which said distal end of
the cuff is in the form of a cylindrical band provided with pleats
extending outwardly across the band to points spaced inwardly from
the outer edge of the band.
Description
A hospital patient requiring intermittent positive pressure
ventilation may have a tube inserted in his trachea by way of the
mouth or nose or by way of a surgically created opening into his
trachea. The distal end of the tube is encircled by an inflatable
cuff to provide a seal against the wall of the trachea. In making
sure that such a seal is adequate, there is a tendency to
overinflate the cuff so that it may press too tightly against the
tracheal wall. Besides discomfort, this can cause serious
complications, such as dilation of the trachea, blockage of
circulation, and necrosis of that portion of the trachea around the
cuff. Various ways have been proposed to prevent overpressurizing
of such cuffs, but most of them have not been successful or have
been so complicated that they have not been used properly.
It is an object of this invention to provide an endotracheal or
tracheostomy tube with an inflatable cuff that will produce a safe
pressure controlled good seal against the tracheal wall that will
protect against aspiration during all phases of the ventilatory
cycle. Another object is to provide such a cuff that will
automatically prevent overpressurization. A further object is to
provide a cuff which will automatically cycle its internal pressure
in syncronous response to airway pressure.
The preferred embodiment of the invention is illustrated in the
accompanying drawings, in which
FIG. 1 is a side view of an endotracheal tube, with an
overpressurized cuff shown partly in section and excessive air
escaping from it; and
FIG. 2 is an enlarged view of the cuff from the distal end of the
tube.
Referring to FIG. 1 of the drawings, a flexible breathing tube 1
that is adapted to be inserted in the trachea T in a well-known
manner has an outer or proximal end that is exposed for connection
to breathing apparatus (not shown) by which air can be forced into
the lung periodically. The tube is encircled near its inner or
distal end by an elastic cuff 2, preferably about five centimeters
long and three centimeters in diameter when inflated but
unstretched and unpressurized. The opposite ends of the cuff have a
much smaller diameter than the area between them and normally both
fit tightly against the tube. The cuff can be inflated by air
forced into it by means of a syringe 3 or the like, temporarily
connected to the outer end of a very small diameter tube or tubule
4 that extends along the main tube and into the inside of the cuff.
In one make of endotracheal tube the tubule is molded into the wall
of the tube and has an outlet 5 from its distal end into the cuff.
After the cuff has been inflated, the syringe is removed and the
outer end of the tubule is clamped or plugged to maintain the
desired air pressure in the cuff.
It is a feature of this invention that the cuff cannot be
overinflated except momentarily. Accordingly, although the proximal
end 7 of the cuff is sealed against the tube, such as by an
adhesive, the major portion of the distal end 8 of the cuff is not
attached to the tube. It need be tacked to the tube at only one or
two points to prevent it from sliding along the tube. For example,
a stitch or a spot of adhesive 9 may hold the end of the cuff in
place. The rest of the distal end of the cuff is free to be
stretched radially away from the tube in case the air pressure in
the cuff is excessive. Consequently, the distal end of the cuff
serves as a check valve. In this connection it should be noted that
it is not the air pressure alone inside the cuff that is the
determining factor regarding opening the valve, but it is the
pressure gradient or drop across the check valve; that is, the
difference in air pressure between the inside of the cuff and the
air pressure in the trachea below the cuff. This pressure drop
exists only during exhalation, when the pressure in the lungs drops
to approximately zero. If the pressure inside the cuff at that time
is greater than the cuff is designed for, the excess pressure will
be relieved because it will stretch the check valve 8 radially away
from the tube sufficiently to allow air to escape from the cuff
until the intracuff pressure is back to a safe value.
During inflation of the lungs by the breathing apparatus, the
pressure drop across the check valve becomes zero because the air
pressure in the trachea below the cuff and the air pressure inside
the cuff are equalized. In other words, as the air pressure in the
trachea below the cuff starts to exceed the normal pressure within
the cuff, the lower end portion of the cuff is compressed and that
reduces the internal volume of the cuff and causes the intracuff
pressure to increase to balance the air pressure in the trachea.
The check valve is held closed by the increased air pressure around
it. There is thus no danger of cuff deflation when high airway
pressures are necessary for patient ventilation. Although at this
time the pressure of the cuff against the wall of the trachea is
increased, it has no more injurious effect on that wall than the
pressure of the air against it below the cuff.
It will be seen that it is absolutely necessary that it be the
distal or lower end of the cuff that serves as the check valve to
permit excessive air pressure to escape from the cuff. If this
valve were formed by the upper end of the cuff instead, during
inflation of the lungs the air pressure in the trachea below the
cuff would squeeze the air out of the upper end of the cuff and
thereby deflate it.
To control the opening of the check valve formed by the distal end
of the cuff, it has been found best to make that end in the form of
a cylindrical band as shown, so that an appreciable area of the
tube will be engaged by the cuff, rather than providing merely line
contact between them. The band may be about 5 mm long, although it
may be provided with pleats that extend from its inner edge part
way out to its free outer edge so that the inner area of the band
will expand and separate from the tube easily as overinflation
starts to occur, whereby the threshold pressure for cuff
decompression is controlled more exactly. It also has been found
best to design the cuff so that a pressure drop across the check
valve that does not exceed about 20 mm of mercury during exhalation
will not open the valve. If, due to too much air being forced into
the cuff through the tubule, the pressure drop becomes greater than
that, the check valve will open and permit enough air to escape
from the cuff to reduce the pressure drop to 20 mm of mercury. Even
if positive-negative pressure ventilation is used, the valve will
remain closed if the resting intracuff pressure is 15 mm of mercury
and the negative pressure during the negative phase of ventilation
does not exceed 5 mm of mercury.
The cuff and tube should be made of materials that will not stick
together where the distal end of the cuff engages the tube. If
rubber is found to present such a problem, the tube and/or cuff can
be made of some such material as Dow Corning's Silastic.
Another important advantage of this cuff is that if the patient is
not being ventilated effectively and if he is capable of making
inspiration efforts of sufficient magnitude, he can actually suck
the air out of the cuff through the check valve and thereby
collapse the cuff so that he can inhale around it.
With this cuff the intracuff pressure is independent of the skills
of those who may inflate the cuff, because the check valve will
automatically take care of too much air pressure in the cuff.
Consequently, the pressure of the cuff against the wall of the
trachea likewise is controlled automatically.
According to the provisions of the patent statutes, I have
explained the principle of my invention and have illustrated and
described what I now consider to represent its best embodiment.
However, I desire to have it understood that, within the scope of
the appended claims, the invention may be practiced otherwise than
as specifically illustrated and described.
* * * * *