Hydraulic Cuff Tracheal Tube

Abstract

Hydraulic cuff tracheal tube system for respiratory air has cuff filling means comprising a readily collapsible, non-pressure applying filling container connected to the cuff through the flexible filling lumen. The container, lumen and cuff comprise a closed liquid system. The lumen and container extend a predetermined distance from the cuff equal substantially to the gravity head desired in the cuff, e.g. 20 centimeters H.sub.2 O. When the container is raised above the cuff, the system is capable of permitting free-flow of liquid into the cuff under influence substantially only of the gravity head with attendant non-pressure-applying collapse of the container. There is shown a collapsible container bag formed of flaccid material, thin plastic sheet or film. A releasable sealing means between the cuff and container prevents flow of liquid into the cuff prior to need; and when reset prevents loss of gravity head pressure after filling of the cuff. With the assembly adapted to receive liquid at the point of use it includes a member through which liquid can be introduced; prior to this the container is in a state of collapse, preferably evacuated. A container may be separable from the cuff and have a seal for preventing escape of liquid when standing alone. Preferably the total volume capacity of the system is about twice the amount of liquid therein and causes part of the system always to be in a collapsed state.

Description

This invention concerns tracheal tubes, i.e. endotracheal tubes and tracheostomy tubes, which are sized and adapted for insertion into the trachea of a patient for introducing and removing respiratory air from the lungs. I have previously proposed the use of a hydraulically-inflatable cuff for the tracheal tube. This cuff surrounds the tube and is flaccid and larger than the diameter of the trachea. By filling this cuff with liquid while it is surrounded by the tracheal wall it is possible to achieve a seal in the trachea with a gravity head of less than 25 centimeters of water, e.g. 15 centimeters. During assisted respiration using a ventilator the pressure in the airway above that level is transferred to the cuff in accordance with Pascal's law and the thus elevated pressure of the cuff insures an adequate seal. Upon relaxation of the pressure of the ventilator the liquid in the cuff returns to its normal base pressure set by the gravity head, this pressure being sufficient to block aspiration of solids. Thus at the times of relaxation of the ventilator the pressure exerted by the cuff upon the tracheal wall can be guaranteed to be well below the transcapillary pressure in the mucous membrane. This assures blood flow to the mucous membranes and deeper structures of the trachea. Thus tracheal damage can be minimized. Despite these advantages of the hydraulic cuff, however, this prior art teaching has not been accepted by the medical profession. One of the objects of this invention is to provide a system which is acceptable to the medical profession in terms of simplicity of use, assurance of safety and guarantee of a safe pressure in the cuff. Another object of the invention is to provide a hydraulic cuff system which is simple and inexpensive.

According to the invention the filling means for the cuff comprises a collapsible, non-pressure applying filling container connected to the cuff through the flexible filling lumen. The container, lumen and cuff comprise a closed liquid system, the lumen and container extending a predetermined distance from the cuff equal substantially to the gravity head desired in the cuff. This gravity head normally is less than 25 centimeters and preferably is in the range of about 15 to 20 centimeters. In operation the container contains on the order of between 10 and 25 cubic centimeters of liquid, depending upon the length and size of the cuff chosen. The system, when the container is raised above the cuff, is capable of permitting free-flow of liquid from the container into the cuff under influence substantially only of the gravity head, with attendant non-pressure applying collapse of the container.

Other objects and features of the invention will be understood from the abstract, to which reference is made, and from the following description of a preferred embodiment with reference to the drawings wherein:

FIG. 1 is a plan view of a preferred embodiment of the hydraulically inflatable cuff endotracheal tube system of the present invention;

FIG. 2 is a partially cross-sectional and diagrammatic view of the system of FIG. 1 inserted into a patient;

FIG. 3 is a view similar to a portion of FIG. 2 but on a larger scale, showing the cuff under the influence of Pascal's law in the trachea during inspiration of air;

FIG. 4 is a partially diagrammatic side view of a preferred container according to the invention.

FIG. 5 is a view similar to FIG. 1 of a preferred embodiment of a tracheostomy tube system of the present invention, FIG. 6 being an edge view of the collapsed container of FIG. 5.

Referring to FIGS. 1-3 a tracheal tube, here endotracheal tube 10, has the usual distal opening 12 for introducing air into the trachea and a proximal connector 14 for connection to a respirator apparatus. Near the distal end of the tube a cuff 16 of flaccid collapsible material such as 0.001 inch thick polyethylene or cellophane or preferably latex is collapsed about the tube. Leading from the cuff is a flexible filling lumen 18 of approximately 1/16 inch internal diameter which extends separate from the tube past a releasable sealing valve, here clamp 20, to a collapsible container 22. The container in this embodiment comprises a bag formed of flaccid material, such as latex or polyvinyl chloride sheet or film. (For example it may be of 0.003 inch thickness stock, and comprise two side walls 1 inch wide and 2 inches long, heat sealed at bottom and sides, much in the nature of conventional consumer-sized mustard and ketchup packs.) The cuff 16, the filling lumen 18 and the bag 22 define a closed liquid system. The lumen 18 and the container 22 extend a predetermined distance L from the cuff, here 25 centimeters, a distance equal substantially to the gravity head, 20 cm,desired in the cuff when the cuff is to establish its seal. Referring to FIG. 2 the endotracheal tube is shown inserted into a patient with the cuff 16 disposed within the trachea. After insertion the cuff is filled through the procedure of opening the valve 20 and raising the container to the vertical height H, limited by the length of the lumen L, height H equaling the gravity head desired in the cuff. Liquid then flows by gravity through the filling lumen, expanding the collapsed cuff 16 and at the same time the bag 22 undergoes non-pressure applying collapse as the liquid freely shifts in the system. Although the cuff 16 is larger than the trachea, it is prevented from expanding to its full dimension by the tracheal wall which it engages, and thus the amount of liquid transferred from the bag into the cuff is less than that which the cuff could hold if it were in a free state. After equilibration, valve 20 is again closed, thus assuring the desired base pressure in the cuff. Referring now to FIG. 3 upon inspiration, as air is forced by the respirator through the endotracheal tube into the lungs of the patient, back pressure of the air P transfers to the cuff wall and displaces the liquid rearwardly into a tear drop shape. The cuff is thus pressed against the tracheal wall with a pressure equal to the airway pressure P in accordance with Pascal's law. Upon reaching the rest portion of the respiratory cycle, when air neither flows into or out of the lungs, the pressure in the cuff returns to the base pressure established by the original height H of the collapsible bag. Upon expiration a reverse effect may be observed.

For an adult sized endotracheal tube according to the invention the cuff is preferably on the order of an inch or an inch and a half in diameter and in length, and the bag is supplied with 15-20 centimeters head of water sealed therein. This can be used for patients from 75 lbs. up. When the cuff and endotracheal tube are inserted into a patient as shown in FIG. 2 and the container raised to the predetermined vertical height H set by the length L of the filling lumen, the amount of water drained from the container into the cuff varies according to the size of the trachea. Thus for a small female patient, only half of the amount of water in the container may drain into the cuff before the wall of the trachea restricts and stops the flow. In the case on the other hand of a large male patient, virtually all of the liquid may flow out of the container and the container virtually completely collapses due to the larger expanded volume of the cuff permitted by the larger trachea of this patient. Since however the container is only on the order of 5 centimeters total vertical length, the difference in head between these two extremes may be on the order of one or a few centimeters of water.

After the cuff is filled and the valve 20 reclosed the container may be dropped on the patient's chest or pinned in a convenient place and is readily available for reequilibration of the pressure as may be done by the nurse on duty every 8 hours.

Referring to FIG. 4 there is a preferred embodiment of a container in which a collapsible bag 22 is housed in a rigid polyethylene bottle 24. The purpose of this bottle is to protect the bag 22 from outside exertion pressure. It will be understood that if the attending physician inadvertently squeezed the bag 22 while filling the cuff, this could increase the pressure in the cuff 16 far above the gravity head established by the height of the collapsible bag. This could produce pressures far in excess of the transcapillary pressure in the mucous membran and therefore would present danger of deprivation of blood in the tissue with consequent necrosis.

The protective container 24 has openings 26 which allow the entry of air into the container 24, enabling ready collapse of the bag 22 when the valve 20 is released. Advantageously in certain instances the bag 22 and container 24 combination can be packaged separately from the endotracheal tube with a self-sealing rubber plug 28 inserted in the end of the bag. This plug, similar to that of a valve for filling a basketball, can be connected through an appropriate needle to the lumen to complete the closed liquid system.

Referring to the embodiment of FIGS. 5, and 6, here tracheostomy tube 10a has a cuff 16 similar to that shown in FIG. 1, with a lumen 18, valve 20 and collapsible non-pressure applying bag 22. The bag and cuff are collapsed, a side arm 23 defines a self-sealing entry point for hyperdermic filling needle 30, which, with valve 20 remaining closed and cuff 16 collapsed, can introduce the filling liquid into the system. After such filling and removal of the needle, valve 20 can be opened to allow flow of liquid into the cuff as previously described.

Although itself quite simple, the collapsible, non-pressure applying bag has important result in making practical a system which has heretofore been judged to be impractical and not acceptable to the medical profession. In other words a closed system insures that no liquid is lost, and the amount of liquid contained in the closed system is less than what can easily be tolerated by release into the lungs should a leak occur. The presetting of the length L of the filling lumen establishes the maximum height H to which the container can be raised, and thus establishes a maximum hydrostatic head in the cuff. Advantageously this head is less than 25 centimeters of water, and preferably in the range of 15 to 20 centimeters of water. A further advantage is that the liquid can be maintained in a sterile state and growth of bacteria can be eliminated.

A further advantage is that liquid, surface effective anesthetic can be provided in the bag 22 and, if the cuff 16 is made of diffusion membrane then the advantage of surface anesthetization of the tracheal tissue can be obtained as described in my previous U.S. Pat. No. 3,348,542.

Other embodiments are possible and are within the scope of the following claims.

Claims

What is claimed is:

1. In a hydraulic cuff tracheal tube assembly including a tracheal tube adapted for insertion into the trachea of a patient, for introducing and removing respiratory air, a cuff surrounding the distal end of the tube, the cuff being larger in diameter than the diameter of the trachea, pliable and readily collapsible, and a filling means including a flexible filling lumen having a proximal portion separate from and movable relative to said tracheal tube, said lumen adapted to introduce liquid into said cuff for distending the cuff and enabling the cuff to be sealed against the tracheal wall,

the improvement wherein said filling means comprises a collapsible, non-elastic, non-pressure applying container for containing filling water and connected to the proximal end of said flexible filling lumen, to communicate there-through with said cuff, said container, lumen and cuff comprising a closed liquid System, said lumen and container extending a predetermined distance from said cuff corresponding to a preselected fill pressure measured in inches of water, said pressure being less than that pressure which can cause damage to the tracheal tissue, said assembly enabling the container to be vertically spaced from said cuff said distance and produce said preselected gravity head pressure on the tracheal wall by said cuff through free flow of liquid from said container into said cuff, with attendant non-pressure applying collapse of said container.

2. The assembly of claim 1 wherein said collapsible container comprises a collapsible bag formed of flaccid material.

3. The assembly of claim 2 wherein said bag is defined by flexible plastic sheet.

4. The assembly of claim 1 wherein said container extends less than 25 centimeters from said cuff and said closed liquid system is adapted to contain water.

5. The assembly of claim 1 adapted to receive liquid at the point of use, said assembly including a sealing member through which liquid can be introduced into said container, a releasable valve means for preventing flow of liquid into said cuff until desired, said container being in a state of collapse.

6. The assembly of claim 5 wherein said system formed by said cuff, lumen and container is evacuated.

7. The assembly of claim 1 wherein said closed system contains liquid of a volume equal to about one half the total volume capacity of said system, at least part of said system always residing in a partially collapsed state.

8. The assembly of claim 1 wherein said container is separable from said cuff, the container having a seal for preventing escape of liquid when standing alone, the container being attachable to said system and said seal being openable to permit said free flow.