US 3788326 A
A balloon or cuff is combined with a distally perforated soft plastic tracheal catheter over a wedge in the middle part of the catheter. The catheter is molded from non-pyrogenic thermoplastic material such as polyethylene, polytetrafluorethylene, polypropylene, poly-carbonate or other readily sterilized orientable material which is precurved at its proximate end for insertion percutaneously or is straight for insertion through the mouth and is perforated at its distal end to divert part or all of the ventilating stream passing through the catheter. If improper positioning of the axial outlet in relation to the tracheal lumen occurs, these distal perforations in the straight and precurved species permit air under pressure to be diverted from the axial outlet thereby preventing air embolisms while the air passing through the wedge blows up the balloon to press it against the trachea. These air embolisms occur and are created due only to the diffusion of air into the tissues impinged upon by the high pressure oxygenated gas flow at the axial outlet. At normal flow with proper placement no more than ten to twenty-five percent of the air passes out of the sides and this diversion maintains the desired medial axial positioning of the catheter in the tracheal lumen.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Jacobs [451 Jan. 29, 1974 DISTALLY PERFORATED CATHETER FOR USE IN VENTILATING SYSTEM  Inventor: Harvey Barry Jacobs, 116-13 Vantage Hill Rd., Reston, Va.
 Filed: Aug. 3, 1972  Appl. No.: 277,627
Related US. Application Data  Continuation-impart of Ser. No. 59,206, July 29,
1970, Pat. N0. 3,682,166.
 US. Cl. 128/305, 128/351, 128/349 B  Int. Cl A61m 25/00  Field of Search... 128/305, 329, 343, 344, 347,
128/349 R, 349 B, 351, 129, 3, 2 M, DIG. 9,
 References Cited UNITED STATES PATENTS 3,459,189 8/1969 Alley et a1. 128/221 3,680,562 8/1972 Wittes 128/347 3,800 10/1844 Gale 128/349 R 3,459,188 8/1969 Roberts 128/347 1,740,174 12/1929 l-levern 128/349 3,707,151 12/1972 Jackson 128/349 B 3,182,663 5/1965 Abelson 128/351 3,653,388 4/1972 Tenckhoff... 128/347 3,688,773 9/1972 Weiss 128/305 2,976,865 3/1961 Shipley.... 128/349 R 3,398,747 8/1968 Raimo 128/351 FOREIGN PATENTS OR APPLICATIONS 229,749 7/1969 U.S.S.R 128/329 Primary ExaminerRichard A. Gaudet Assistant Examinerl-lenry .1. Recla Attorney, Agent, or FirmAbraham A. Saffitz [5 7] ABSTRACT A balloon or cuff is combined with a distally perforated soft plastic tracheal catheter over a wedge in the middle part of the catheter. The catheter is molded from non-pyrogenic thermoplastic material such as polyethylene, polytetrafluorethylene, polypropylene, poly-carbonate or other readily sterilized orientable material which is precurved at its proximate end for insertion percutaneously or is straight for insertion through the mouth and is perforated at its distal end to divert part or all of the ventilating stream passing through the catheter. lf improper positioning of the axial outlet in relation to the tracheal lumen occurs, these distal perforations in the straight and precurved species permit air under pressure to be diverted from the axial outlet thereby preventing air embolisms while the air passing through the wedge blows up the balloon to press it against the trachea. These air embolisms occur and are created due only to the diffusion of air into the tissues impinged upon by the high pressure oxygenated gas flow at the axial outlet. At normal flow with proper placement no more than ten to twenty-five percent of the air passes out of the sides and this diversion maintains the desired medial axial positioning of the catheter in the tracheal lumen. This high pressure is created cyclically, the wedge diverting pressure from within the catheter to blow up the balloon under the pressure cycle of the ventilator and to permit collapse in the succeeding cycle. When air flow ceases through the wedge of the catheter, the elasticity of the balloon is such as to cause the balloon to collapse and rest against the catheter, thereby providing the function of a cuff. The cuff function of the balloon minimizes retrograde air leak during the inflation cycle.
8 Claims, 20 Drawing Figures SHEET 1 BF 4 CRICO THYRO| MEMBRANE TRACHEA/ PATENTEB JAN 29 i8? sum 2 0? 4 DISTALLY PERFORATED CATHETER FOR USE IN VENTILATING SYSTEM This application is a continuation in part of my copending application, Ser. No. 59,206 filed July 29, 1970 now US. Pat. No. 3,682,166.
In my co-pending application, I disclosed a tracheal catheter for use in ventilating systems using air or oxygenated gas and for insertion percutaneously into the tracheal lumen. In my prior patent application, the catheter was made of a plastic material which has a plastic memory and was fabricated in a curved shape in the proximal portion thereof, the catheter being adapted to fit over the outside ofa substantially straight needle and be straightened out by the needle when the needle is pushed through the catheter so that it penetrates into the trachea to have the catheter therein, the curved material causing the catheter to resume the original curved shape as a result of the plastic memory of the material within the trachea after the needle is withdrawn therefrom.
The present invention relates to an emergency trachectomy instrument and ventilating apparatus for restoring breathing to nonbreathing patients due to tracheal obstructions and pulmonary complications, which is also useful for aiding ventilation for bronchoscopy and during general anestheia in which the soft plastic catheter may be either curved or straight but which must be perforated at the distal end to divert part or all of the ventilated stream passing through the catheter. In this manner, any improper positioning of the axial outlet of the catheter will permit release of the oxygen or air into the tracheal lumen. Only in this manner will there be overcome air embolisms which occur in the use of the precurved catheter of my parent application. It has been surprisingly discovered that only if the normal axial flow ofthe oxygenated gas is diverted through distal openings of the catheter can the accidents of improper positioning be avoided so that serious and automatic self-injury is not done to the patient or animal treated with the emergency resuscitating apparatus of the present invention. Indeed, the need for curving can be dispensed with and a straight catheter, having great advantages for proper placement, has been developed under the present invention which is uniquely adapted for pediatric resuscitation.
In another embodiment of the invention, an elastic balloon or cuff is provided, inflatable by the same oxygenated gas stream, which is cyclically introduced into the trachea for resuscitation, the elastic balloon being operative under diverted air pressure created within the catheter structure by providing a wedge in the wall of the catheter along the catheter axis. This wedge diverts high pressure oxygenated gas in the inflation cycle and blows up the balloon to minimize retrograde air leak. In the removal of the balloon from the trachea, the elasticity of the balloon is such as to cause the balloon to collapse and rest against the catheter in the absence of high pressure air; in effect, the elasticity permits the balloon to act as a cuff inflatable under the inflation cycle and being contracted and displaced toward the catheter wall when the air is cut off (easy removal). The cuff structure is unique and simple and distinguishes over the prior art cuff structures by being operative solely under the action of the ventilating oxygenated gas directed through the axis of the catheter.
As a result of the combination of the cuff and the distal openings diverting at least ten to twenty-five percent of the air under normal axial placement in the proper position as shown in the parent case, Ser. .No. 59,206, a new and unexpected function of the transversely displaced air stream outflowing from the distal openings results which positions the soft yet flexible catheter in an assured operatively safe location within the trachea. The inventor discovered in working with animals that air embolisms caused death when difficult resuscitations were attempted in the presence of secretions in the back of the mouth area. Despite the fact that the secretions were blown out and that successful insertions were very easily accomplished within a few seconds, the failures were due to axial air flow of pressures of 30 to psi to create microscopic bubbles in the capillaries along the tracheal linings constituting the cause of death. These embolisms in the capillaries presented a mystery over a long period of time which were only solved by autopsy. It is the object of this invention to provide a percutaneous transtracheal catheter ventilator which can be inserted by a physician, nurse, or technician in less than ten seconds, simply plugged into the wall oxygen outlet or or oxygen tank, operated manually or automatically as desired, and have the safety and ease of insertion that will not commit the patient to a permanent type tracheostomy or the danger which tracheostomy generally entails in an emergency.
Prior efforts to introduce cuff or balloon catheters have not been practical since the emergency insertion requirement cannot be achieved and a further object of the invention is, accordingly, to provide a cuff apparatus which is operative solely under the influence of the axial gas flow within the catheter to prevent retrograde air leak during the inflation cycle.
The closest type of cuff structure which the inventor has found in the prior art is that shown in Schossow, U. S. Pat. No. 3,087,493 relating to a bulky endotracheal tube with a cuff structure but this cuff structure requires a separate pressurized gas means to inflate the cuff and the structure is so complex in respect to the patient management and maintenance of free airway passages that it requires a generalanesthetic in order to introduce the catheter or tube into the respiratory passages of the patient. Obviously, the Schossow tube is not suitable for emergency insertion by semi-skilled or paramedical personnel who have no facilities in ambulances or emergency units to perform major surgery.
Other types of tubes in the prior art, curved as well as straight, have been provided; for example, Williams, U. S. Pat. No. 340,190, or Gale, U. S. Pat. No. 3,800, patented Oct. 16, 1844, but these tubes are in no way suitable for introduction into the throat for life-saving ventilation under emergency conditions. It is only the present catheter of soft plastic material with distal openings which must withstand high ventilating pressures yet be simply positioned by semi-skilled personnel to save the lives of the patients within the first ten seconds and can be employed with the positive assurance that the distal openings will compensate for any variation in performance by the nurse, technician or doctor.
Still other surgical type catheters are known; for example, Petersen, U. S. Pat. No. 3,490,457, shows a syringe type catheter which, because of its structure, cannot provide the self-orientation characteristics of the present self oriented catheter. The passage of ID to 25 percent of the air in the transverse crush as a result of axial in-flo provides a self-orientation responsive only to the oxygenated gas which comes into the respiratory system of the patient through a single channel. This simplicity permits entry through the mouth or nose or throat or through the crico-thyroid membrane.
Accordingly, a further object of the invention is to provide a straight perforated catheter which is selfadjusting under the influence of incoming high pressure oxygenated gas through the longitudinal axis of the catheter when it is placed within the trachea of the patient, the distal openings in the catheter providing a minimum of 10 and up to 25 percent of transverse air leakage to the catheter within the trachea, thus preventing air embolisms.
Other and further objects and advantages will be apparent from the following description accompanying drawings, wherein:
FIG. 1 is a cross-sectional view of the distally perforated catheter in precurved shape;
FIG. 2 is a perspective view of the perforated catheter of FIG. 1 in its free state;
FIG. 3 illustrates the position of the perforated catheter of FIG. 1 in relation to the trachea;
FIG. 4 illustrates the position of the free perforated catheter of FIG. 1 in the trachea, the catheter having assumed its normal curved shape;
FIG. 5 is a showing of the fitting of the adapter means of my co-pending application titled Ventilating Apparatus Embodying Selective Volume or Pressure Operation wherein the plunger unit and adapter are combined with a catheter of the invention, illustrated in only the form of that in FIG. 1;
FIG. 6 is a cross-sectional view along line 6 6 of FIG. 5;
FIG. 7 is a view of the catheter of FIG. 5 to show the condition of the cuff in collapsed condition in the absence of pressurized air through the main axis of the catheter.
FIG. 8 is a view of the precurved catheter of FIG. 7 with the balloon or cuff inflated.
FIG. 9 is a cross-sectional view along Line 10 10 of FIG. 9 showing gas circulation through the wedge opening for inflating the balloon, the inner arrows indicating in diagrammatic form the free circulation between inner and outer lumens;
FlG. 10A and FIG. 10B illustrate perspective views of a straight catheter having a premolded balloon adapted for pediatric ventilation wherein a split ring trochar fitted with handles aids in positioning the catheter through the mouth of an infant or other patient and which inflates by partial division of the pressurized gas after the trochar is removed;
FIG. 11 is a sectional view of the catheter of FIGS. 10A and 10B showing the triple lumen structure;
FlG. 12A and FIG. 128 show the use of the split ring adapter in the construction of a modified precurved catheter having multiple feeding inlets for a variety of resuseitating procedures;
FIG. 13 shows a triple lumen adapter means (third lumen is a cuff) which is inflated in the cuff position and is associated with a lower portion of the precurved catheter of FIGS. 12A and 128 to show the partial completion stage;
FIG. 14 is a cross-sectional view of the triple lumen patient adaptor means of FIG. 13 at the level of the proximal partial obstructing tracheal balloon and wedge gas inlet site showing the transient inflation of the balloon and which illustrates cuff inflation by diverting part of the gas stream;
FIG. 15 shows one of the catheters of the longer double lumen pair serving as the minor source of pressurized gas in a conducting and self-cleansing lumen structure with its corresponding distal-perforated catheter serving as the pressure conducting catheter, and the proximal partial obstructing tracheal balloon only transiently inflated;
FIG. 16 shows the orally insertable distal-perforated straight catheter of the double lumen distal pair serving as the minor pressurized gas conducting and selfcleansing lumen (similar to FIG. 15) with its corresponding distal member serving as the pressure conducting catheter, and shows the proximal partial obstructing tracheal balloon transiently inflated;
FIG. 17 shows the proximal portion of the single lumen orally inserted patient adaptor means with its multi-level anchoring and compression withstanding ridges, and distal gas jet diffusing member plug crosssection of the proximal portion at level of a compression withstanding and anchoring ridge; and
FIG. 18 shows a thin distal pressure-sensing trans ducer in conjunction with the single lumen patient adaptor means, passing through said patient adaptor means and relaying distal intrapulmonic pressure values to its attached controlling ventilating means, whereby feedback, monitoring, control and recording functions are provided.
To facilitate study of the details shown in the foregoing FIGS, reference is made to the co-pending application filed on even date herein (Aug. 3, 1972) which bears certain common figures with the present case (which omits the nebulizer hookup). The reference numerals are similar and the following description from the co-pending application (filed same day) identifies the catheter structures as single and triple lumen catheters, the double lumen referring to the cuff or balloon. The reference numerals selected herein correspond to those of my copending application, Ser. No. 59,206, which is, at the time of execution of this application now in issue and therefore need not be repeated. The reference numerals are those of the co-pending case which will issue shortly.
The operation of the cathers of the present inventions are completely described in my original paper in the Journal of Trauma for January 1972 entitled Emergency Percutaneous Trans-tracheal Catheter and Ventilator.
The operation is summarized in terms of connecting, integral, single and triple lumen catheters.
CONNECTING, INTEGRAL, SINGLE AND TRIPLE LUMEN CATHETERS The ventilating machine (FIGS. 1-4) forces air or oxygen under high pressure (30100 pounds per square inch) through the catheter into the trachea, and even in the presence of the air leak through the mouth (retrograde flow), pressures of 15 to 35 cm. water are easily attainable (same pressure reached as present machines that use a closed system large tube and balloon cuff).
When the gas flow is discontinued, the patient exhales out of the normal oral route. In complete upper airway expiratory obstruction (above the catheter entrance site) suction is cyclically provided to aid exhalation. Using the single lumen catheter system the patients ventilation is controlled by the ventilating machine, but with the triple lumen catheter and ventilating system, the patient can control the machine and therefore the assist ventilating mode plus measurement of intrapulmonic pressure as well as gas analysis is made possible. The larger proximal lumen conducts the ventilating gas while one of the other distal lumens alternately transmits the intra-tracheal (intra-pulmonic) pressure level to the sensing device, and conducts the minor high pressurized gas self cleansing flow.
The single lumen patient adaptor means (FIGS. 6-10, 17, 19) has a pressurized gas conduit 251 which conducts the pressurized gas from its connecting hub 256 to its terminal open lumen 264 plus side holes 261. The thick walled inner hollow needle-trochar member 252 traverses the entire length of the pressurized gas conducting conduit 251 and extends beyond each end for a short distance (FIG. 6). The distal portion 293 has a sharp leveled cutting edge plus a small opening 299 which transmits air, when properly located within the trachea, to the proximal syringe 258. The syringe connecting member 259 fits snugly into the needle-trochar hub 257 and is an air tight connection. Air is transmitted through lumen 297 of the needle-trochar unit into the syringe 258, when in proper position by pulling on plunger unit 260. Following proper position, the catheter 251, is advanced into the trachea 265, holding the needle-trochar unit stable. When the catheter flange 253 and hub portion 255 reach the skin the needletrochar is removed. The catheter assumes a pre-molded 90 curve whose radius is one half the respective tracheal diameter, this curve being shown as curve 294 in FIG. 7 and which stabilizes it aimed down the trachea, without pressure on the tracheal wall. Hub 256 has screw locking prong 291 which can screw lock onto the gas conduit from the ventilating machine, as well as receiving its receptable within said hub.
The side holes 261 provided along the catheter act as a safety valve when the end lumen 264 may be located at a poor angle in relation to the tracheal lumen. They also aid in lateral transmission of the pressurized gas (up to 75 percent) when the terminal porous gas diffusing member 287 is attached (FIG. 17). In this instance, insertion is within the breakaway needle trochar when placed through the skin, or passed without a trochar via the oral route. The porous gas diffusing member 287 decreases the constant aimed site of the single gas jet and diminished any local effect possible from it. The catheter has a skin anchoring flange 253 (FIGS. 6, 7, 8) which is firmly fixed and solid with the distal hub portion 255 and a solid part of catheter 251. This flange has holes 254 through which it may be sutured to the skin at the neck entrance site or tapes or strings attached to hold it is place on the neck.
Snugly placed around the catheter 251 and firmly integral to it is a balloon 263. As the pressurized gas flows down the catheter 251 it meets a small degree of resistance at the premolded, resiliant, inner projecting catheter gas inlet wedge 262 (FIGS. 6, 8, 9, 10). This wedge is held flat in position by the inner needle-trochar unit but when the needle-trochar unit is removed, the gas inlet wedge partially springs into the lumen and by its presence channels some gas through its lumen and distends the balloon 263. This proximal tracheal partial obstructing balloon effectively decreases the tracheal opening and therefore decreases the retrograde leak only while the pressurized gas is flowing in catheter 251. This allows the lungs to be distended to the same final pressure and volume by a lesser amount of the pressurized gas.
The single lumen catheter can be passed via the nosopharyngeal or oro-pharyngeal route between the vocal cords and positioned into the trachea. This method is especially desirous in infants and small children. The catheter 251 then does not have pre-molded curve 294 but is straight and has muIti-level anchoring and compression withdranding ridges 285. These allow the catheter to be sutured or taped or tied in proper position through holes 286 at the correct level for each individual patient and prevents catheter 251 from bending to the degree where it will narrow its lumen and also prevents the teeth and gums from compressing the lumen.
The triple lumen patient adaptor means (FIGS. 11-16, 18) utilizes the larger proximal lumen as the main gas conducting catheter while it allows one distal lumen to act as the pressurized gas conducting self cleansing conduit while at the same time the other distal lumen transmits the tracheal (intra-pulmonic) pressure to the ventilating machine. As in the single lumen variety there is a similar skin anchoring flange 253 but with three hubs 301, 302, 303. Each catheter 304, 305, 306, has its own respective lumen 267, 268, 269; respective side holes 270, 271, 272 but only the larger main proximal catheter has a gas wedge inlet 273 to its proximal partial obstructing tracheal balloon 274. As shown in FIGS. 14, 15, 16, 18 the main proximal lumen always acts as the main pressurized gas conducting conduit, while one distal lumen is cleansed by the minor gas flow and at the same time, the other distal catheter transmits the intratracheal pressure back to the ventilating machine. With the next respiration cycle the other distal catheter conducts the gas cleansing flow while the former distal catherer now transmits the tracheal pressure.
The triple lumen patient adaptor means is inserted through a novel breakaway 4 inch long trochar (FIGS. 11, 13). The trochar unit consists of a thick walled sharp straight inner needle 275, the same diameter as the triple lumen patient adaptor means used, with an attached syringe 276. Snugly fitting around this sharp hollow needle is a shorter blunt flat-ended trochar 277 which allows the triple lumen patient adaptor means to pass through it. This blunt trochar has a split shaft 278 and split hub 279 with attached separate wing handles 280, 281. When assembled, the sharp inner needle extends 2 mm. longer than the blunt flat-ended hollow trochar. This is thrust through the skin, then through the crico-thyroid membrane (or crico-tracheal membrane) into the trachea. When air is aspirated back, the intra-luminal position is assured and the blunt trochar is advanced 4 mm further, and held in place while the inner longer needle unit is removed. Next the triple lumen patient adaptor is passed through the blunt splitsided trochar down into the trachea. This is passed until the skin anchoring flange 253 reaches the separate wing handles 280, 281 of the trochar unit. At that moment the blunt split-sided trochar is pulled out of the trachea until its distal blunt end leaves the skin surface,
leaving most of the triple lumen patient adaptor means within the trachea. The separate wing handles are grapsed and bent toward each other, splitting open the whole blunt trochar member 277 (FIG. 13) by the separation of the split shaft edges, and causing it to fall away from the triple lumen patient adaptor means which remains within he trachea. This triple lumen unit has a blunt sliding stiffening rod 282 placed within the larger proximal lumen which now aids the triple lumen patient adaptor means placement further within the trachea by pushing it until the anchoring flange 253 is flush with the skin surface. Then this inner stiffening rod 282 is removed, the pre-molded self-returning 90 curve 294 is assumed and the entire triple lumen patient adaptor means connected to its control ventilating and pressure regulating means. This advancement is also aided by the extra stiffness incorporated in the proximal V2 cm. of the catheter.
The triple lumen separating wall 283 (septum) divides the major gas inflating proximal lumen from the pressure sensing lumens. The wall 284 (septum) separates each of the narrower alternate pressure sensing, self-cleansing lumens.
The triple lumen patient adaptor means may be passed via the oral route between the vocal cords and it also has the anchoring 286 and compression with standing ridges 285 as well as the porous gas jet diffusing member 287 on the main inflating lumen.
The triple lumen patient adaptor means could be constructed of three parallel tubular lumens (one larger proximal and 2 narrower distal lumens) when passed via the oral route.
The single lumen patient adaptor means may have a thin, narrow pressure sensing transducer 288 placed distal to it and have the pressure sensing information conductor 289 passed through it FIG. 18) or through a separate route to the controlling ventilating means with which it works to measure the trachea (intrapulmonic) pressures and utilize this pressure data to regulate, control and monitor the ventilation of the patient.
The length between the wider, larger proximal lumen of the triple lumen patient adaptor means and the distal, narrower double lumen pressure sensing, selfcleansing means is from 1.5 to l cm. depending upon the size of the patient it is utilized in. The larger proximal lumen diameter is from 0.5 to 2 mm. depending upon the size of the patient. The ratio of the single lumen patient adaptor means (and main lumen of the triple lumen patient adaptor means) to the tracheal diameter is from lz6 to 1:50 depenthng upon nastiest the patient, patient disease, patient age and lung compliance as well as whether or not the proximal partial tracheal obstruction balloon is utilized. The patient adaptor means construction is such as to withstand pressures up to 100 psi.
These patient adaptor means can remain in place and be utilized intermittently with the ventilator to give intermittent positive pressure breathing treatments, in-
stillation and nebulization of mucolytic agents and antibiotics as well as measurements of expired air content of oxygen and carbon dioxide.
What is claimed is:
l. in combination, a distally perforated tracheal catheter having an unobstructed wedge opening in the middle portion thereof, and a flat cuff in the form of an elastic balloon which is tightly sealed at its ends above and below said wedge opening, means associated with said opening to divert gas from said catheter into said balloon so that the cyclic passage of high pressure oxygen-containing gas through said catheter inflates the elastic balloon to press against the walls of the trachea with the catheter and cuff in place and deflates to collapse said balloon in flat condition to rest the cuff against the catheter when the high pressure oxygencontaining gas is cut off, said cuff collapsing due to elastic restoring forces of the material of said balloon, said catheter having side openings of such size and number adjacent the distal opening such that under axial flow of high pressure oxygen-containing gas through said catheter diverts from 10 to 25 percent of the gas flow out of said holes and when distal end is plugged permits all of said high pressure gas to be diverted through said side openings, whereby forced ventilation by means of cyclically flowing said high pressure gas through the catheter is aided in the event the end of the catheter is plugged and retrograde air leak during the inflation cycle is minimized by inflation of said balloon during the inflation cycle.
2. The combination as claimed in claim 1 wherein said catheter is precurved.
3. The combination as claimed in claim 1 wherein the distal portion of said catheter is formed with an axial wall to provide a double lumen, the inlet of the double lumen being located below the wedge and cuff seal and the outlet of said catheter having two lumens.
4. The combination as claimed in claim 1 wherein the cuff at its major diameter is surrounded by a split-ring trochar, and grasping means on said trochar to facilitate removal of the trochar from its position surrounding the catheter.
5. The combination as claimed in claim 4 including pressure sensing means at each lumen wherein one of the said two end lumens is used to alternately sense pressure while the other, on an alternate basis, is cleansed by pressureized ventilating gas, and vice versa.
6. The combination as claimed in claim 1 wherein said catheter is straight.
7. The combination as claimed in claim 6 wherein said catheter include anchoring ridge means which resists biting forces when inserted through the patients mouth.
8. The combination as claimed in claim 7 wherein said catheter includes a diffusing means over the axial outlet.