US 3094124 A
Description (OCR text may contain errors)
June 18, 1963 w. c. BIRTWELL ARTERIAL CATHETER 2 Sheets-Sheet 1 Filed June 30, 1960 m m m m WEI/1km azzrrw-zz June 18, 1963 Filed June 50, 1960 w. c. BIRTWELL 3,094,124
ARTERIAL CATHETER 2 Sheets-Sheet 2 INVENTOR. WzY/zkm 6. Bz'rfzra?! Jzfarzays.
United States Patent 3,094,124 ARTERIAL CATHETER William C. Birtwell, North Scituate, R.I., assignor to Davol Rubber Company, Providence, KL, 2 corporation of Rhode Island Filed June 30, 1960, Ser. No. 40,064 1 Claim. (Cl. 128-648) The present invention relates to an arterial catheter. More particularly, the present invention relates to a catheter for use as a surgical accessory and has particular application as an arterial catheter when extracorporeal circulation is required.
In surgical procedures such as cardiac surgery, it is often necessary to shunt the flow of blood around the patients heart through an artificial pumping system, and if the occasion demands, through a pump-oxygenator. In such procedures it is necessary to introduce a catheter into one of the major arteries of the body, the catheter defining the output of the extracorporeal system and being interconnected through tubing to the pump oxygenator. Prior to the instant invention it was the usual procedure to insert a straight catheter into the artery exposed by the surgeon and accordingly the change in diameter from the tubing that was connected to the extracorporeal system to the diameter of the catheter was rather abrupt. The pressure drops associated with such a system and the pressure gradient across the reducing connector that connected the catheter to the tubing of the system was found to be excessive in such instances, thus imposing a limitation on the quantity of blood that could be eifectively pumped through the system. The prior known systems could not compensate for the variations in artery size and consequently it was necessary to have several sizes of catheters available so that the proper one could be selected when the size of the artery to be catherized had been ascertained during the operation. It was furthermore desirable that the relation between the pressure drop across the catheter and the flow be known and it was the usual procedure prior hereto to calibrate the catheters. This calibration was advisable since most catheters as presently used vary too greatly to afford effective comparison without individual calibration.
Accordingly, it is an object of the present invention to provide an arterial catheter for use in extracorporeal circulation that is adapted to produce nonturbulent flow.
Another object of the present invention is to provide an arterial catheter, a portion of which has a gradually decreasing taper, the tapered portion being marked at predetermined intervals to indicate the inside diameter thereof.
Still another object is to provide an arterial catheter that is adapted to minimize pressure drops with resulting turbulent flow when utilized in extracorporeal systems, thereby minimizing hemolysis and other deleterious effects on the blood during surgical procedures which incorporate such extracorporeal systems.
Still another object is to provide an arterial catheter having a decreasing taper that is adapted to be severed at a predetermined point along the tapered portion thereof, a metallic cannula being insertable into the severed portion of the catheter.
Still another object is to provide a catheter having a decreasing tapered portion, on the surface of which indicia are marked for indicating reference points along the length thereof, the reference points designating the point at which the catheter may be severed to produce a predetermined diameter at the distal end thereof as used in a surgical procedure.
Still another object is to provide a plurality of metallic cannula of varying inside diameters that are adapted to be utilized in connection with a hollow, flexible body, the
body being severed at a predetermined reference point and receiving the corresponding cannula therein.
Other objects, features and advantages of the invention will become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.
In the drawings which illustrate the best mode presently contemplated by me for carrying out my invention:
FIG. 1 is an elevational view of the arterial catheter embodied herein showing the tapered portion having the indici-a marked thereon;
FIG. 2 is a sectional view taken along lines 22 in FIG. 1;
FIG. 3 is a view similar to FIG, 1 showing the tapered portion severed at a reference point marked by one of the indici-a, the severed part defining the distal end of the catheter as used;
FIG. 4 is an end view of the proximal end of the catheter;
FIG. 5 is an end view of the distal end of the catheter;
FIG. 6 is a perspective view of one of the cannula shown in FIG. 9'.
FIG. 7 is an elevational view with parts shown in section of one of the cannula shown in FIG. 6 as it is inserted into the severed distal end of the catheter;
FIG. 8 is an elevational view of the severed tapered portion of the catheter showing the cannula installed in the distal end thereof; and,
FIG. 9 is a perspective view of a kit in which a plurality of metallic cannula are mounted, the cannula being indicated by numbers in accordance with the size thereof.
The catheter embodied in the present invention has particular application for use in an extracorporeal system wherein the flow of blood from the patients heart is shunted through an artificial heart, and if the occasion demands, through a pump-oxygenator which arterializes the blood before returning it to the patients system. Thus the pump-oxygenator may be utilized to sustain a patients per-fusion without the benefit of the patients heart and lungs during heart surgery, or it may be employed to support by extnacorporeal means the perfusion of a patient whose heart for any reason is incapable of maintaining an adequate perfusion rate. The problems in either case are similar and relate largely to the requirement for the physiological introduction of a relatively high flow of blood into one of the smaller arteries with a minimum of turbulence, hemolysis and pressure drop. Since it is desirable to reduce the pressure drop gradually across the connector from the extracorporeal system to the patients artery, it is not desirable as has been done heretofore to have an abrupt reduction from the tubing size used in the extracorporeal system to catheter size in a relatively short connector to which is attached a straight catheter. Studies have shown that pressure drops associated with such a system and the pressure gradient across the connector are excessive, thus imposing :a limitation on the quantity of blood which may be effectively pumped through the system.
In one form of the invention, the catheter is formed with a tapering portion that tapers from tubing size to the minimum catheter size over an eight inch distance Graduation marks are imprinted along the taper and indicate calibrated sizes of the inner diameter of the tapering portion which is maintained from catheter to catheter. The catheter is formed of a flexible material and therefore may be cut off at the time of the operation to the size indicated by the exposed artery. The graduation marks on the catheter make possible the uniform calibration of the catheter so that the surgeon may know the relation between flow and pressure drop without calibrating each individual catheter. The blood is thus uniformly and gradually accelerated in the long taper of the catheter thus minimizing hemolysis, turbulence, and other deleterious effects on the blood.
Referring now to the drawings and particularly to FIGS. 1 and 2, the catheter embodied herein is illustrated and is generally indicated at 10. The catheter 10 is formed in a hollow elongated tubular body 12, the inside diameter of which is uniform from the proximal end thereof and for a portion of the length thereof. The catheter 10 tapers gradually from the body portion 12 to the distal end thereof, the inside diameter of the tapered portion as shown in FIG. 2 gradually decreasing to a minimum dimension. In order to effectively utilize the catheter it) with different size arteries, the tapered portion 14 is adapted to be severed at predetermined reference points along the length thereof, and for this purpose the material from which the catheter is formed is of a flexible nature, such as plastic or rubber, and the catheter is preferably manufactured by the dipping process. It is desirable that the relation between the pressure drop across the catheter and the flow of blood be known, and for this reason the catheter may be calibrated so that the dimension of the distal end thereof will be ascertained definitely for the purpose of introducing it into a corresponding size artery. In order to make possible the uniform calibration of the catheter so that the surgeon performing the operation may know the relation between the flow and pressure drop without calibrating each individual catheter, the tapered portion 14- is marked with graduations such as dots or lines at predetermined intervals, and as illustrated in FIG. 2 the lines or dots are identified by imprinting suitable indicia such as numbers adjacent thereto. As shown in FIGS. 1 and 3 the lines which represent reference points are designated by numerals 1 to 7, and as will be apparent, the inside diameter of the tapered portion 14 at these reference points may be definitely ascertained and precalibrated. During the operation the size of the artery is determined when it is exposed by the surgeon. At this point the tapered portion 14 may be severed at the indicated reference point so that the distal end of the catheter will be formed with the prescribed dimension. Assuming that during the operation the artery exposed and to be catherized has an approximate inside diameter that is represented by the reference point No. 1, the tapered portion 14 is then severed as indicated in FIG. 3 at the reference point indicated by numeral 1, and the distal end of the catheter as so formed is then ready to be inserted into the artery. The graduation or reference marks on the tapered portion 14 of the catheter 1ft enable the uniform calibration thereof to be made so that the surgeon may know the relationship between the fiow and pressure drop without having to calibrate each individual catheter. Thus the blood is uniformly and gradually accelerated in the long taper 14 which minimizes the pressure gradient to which the blood is exposed and further minimizes hemolysis, turbulence and other effects on the blood. As indicated above, in use the distal end of the catheter 10 is introduced directly into the artery and may be tied therein by retention sutures if it is so desired.
In any phase extracorporeal circulation, when blood is removed from the patient and through an artifical system, the important factors to be considered are the pressure drop across the catheter at various flow rates, the velocity of the blood emerging from the catheter, and the pressure gradient across the reducing connectors. Since the velocity of the jet emerging from the catheter at any flow is an inverse function of the cross-sectional area of the lumen, the thickness of the wall of the catheter will be instrumental in determining whether proper flow will be established. In most catheters the wall thickness is appreciable when compared to the inside diameter thereof and the ratio of the outside cross-sectional area to the inside cross-sectional area has been found to be as much as 5 to 1. The effect of such a reduction of the lumen on the velocity of'the stream of blood is such as to increase the velocity of the stream required for any flow.
Hemodynamically, the high pressure drop or turbulence resulting from such a reduction of the lumen may be dangerous to the patient and if possible should be avoided. Consequently, it has been found that rather than insert the distal end of the catheter directly into the artery, which technique would produce the reduction of the lumen as indicated, a thin-walled stainless steel cannula may be used in conjunction with the catheter, the combination of the catheter and the thin-Walled cannula being the most satisfactory solution to the hemodynamic or hydraulic problem of re-entry of the blood. By providing a plurality of the stainless steel cannula, the inside diameters of which correspond to the inside diameters of the tapered portion of the catheter at the reference points, a wide range of arteries may be anticipated. As described above the arterial catheter 10 is formed of a flexible material and it is adapted to be severed at any of the reference points extending along the tapered portion thereof. A corresponding cannula may then be inserted in the distal end of the catheter as severed, the resulting inside diameter of the catheter and the associated cannula being of that size necessary for the purpose of carrying out extracorporeal circulation in a particular patient. The tapered catheter and the stainless steel cannula used in conjunction therewith produces a constant non-turbulent flow against a constant back pressure that enables extracorporeal circulation to be successfully carried out.
Referring now to FIGS. 69, the application of the thinwall cannula in combination with the catheter 10 is illustrated. One of the cannula that is adapted to be utilized with the catheter 10 is shown in FIG. 6 and is generally indicated at 16. The cannula 16 is formed of a metallic material such as stainless steel and includes a shank 18 that terminates in an inclined or feathered tip portion 20, the tip portion 25) being the end that is inserted into the artery of the patient. Joined to the end of the shank 18 opposite the tip portion 20 is a head member 22 that is enlarged with respect to the shank 18. The outer surface of the head member 22 is tapered so that the larger end thereof is located adjacent the shank 18 and defines a shoulder 24 therewith. As illustrated in FIG. 7, the wall of the cannula 16 that defines the shank 18 is relatively thin but since the material from which the cannula is formed is stainless steel a rigid constructionis defined. The inside diameter of the cannula 16 is predetermined and extends throughout the length thereof, including the portion that extends through the head member 22. As will be more fully described, the cannula 16 that is selected for use with the catheter has an inside diameter that corresponds to the inside diameter of the severed portion of the catheter, and in use the inclined or feather tip 20 of the cannula is adapted to be easily inserted into the exposed artery. Due to the thin wall of the cannula the reduction in lumen size from artery to cannula is negligible. Since the inside diameters of the cannula and the severed portion of the catheter are substantially equal, the blood is uniformly and gradually accelerated in the long taper, thus minimizing the pressure gradient to which the blood is exposed, minimizing hemolysis, turbulence, and other deleterous effects on the blood normally associated with arterial catheters known heretofore.
Again referring to FIGS. 7 and 8, it is seen that the cannula 16 is firmly retained in position Within the distal end of the catheter 10 by frictional engagement of the severed tapered portion and the enlarged head member 22. Since the material from which the catheter 10 is formed is relatively flexible, the head member 22 may be forced into the distal end thereof, the head member enlarging the distal end as it is pushed therein. Although the cannula is tightly engaged with the catheter as shown, it may be desirable to insure that the cannula is completely immobilized and for this purpose, sutures indicated at 28 in FIG. 8 may be tied around the ends of the catheter and below the shoulder 24 of the cannula. It will be noted that in this position, the cannula 16 has been forced inwardly of the catheter a sufficient distance to enable the distal end of the catheter to engage a substantial portion of the shank 1-8, whereafter the sutures may be applied thereto.
As described above, the tapered portion 14 of the catheter is provided with a plurality of graduation markings that define reference points for indicating predetermined inside diameters along the length of the tapered portion '14. It is apparent that if a cannula is to be inserted into the distal end of the catheter as severed the inside diameter of the cannula must correspond to the inside diameter of the severed portion. For this purpose a plurality of cannulae are provided and are arranged in a kit that includes a block 30' Shown in 'FIG. 9. The block 30 is formed with a plurality of openings 32 in the upper surface thereof, each of the openings 32 varying in diameter and being adapted to receive a cannula therein similar to the cannula 16 shown in FIG. 6. The cannulae mounted in the block 30 are numbered '1 through 7 as indicated and the inside diameters thereof have been calibrated to correspond to the inside diameters of the reference points on the tapered portion 14 of the catheter which bear thecorresponding numbers. Thus if the surgeon determines that the artery exposed during the operation will take a No. 1 cannula the catheter is severed at the number 1 reference point as indicated in FIG. 3, and the number 1 cannula is then inserted into the severed distal end of the catheter. Hence each of the cannula correspond to a reference point and will be selected for use therewith, the selection thereof being determined by the requirements of the exposed artery.
The block 30 also is employed as an aid in interconnecting the cannulae with the catheter and as shown, the cannulae are mounted in the openings 32 with the head members thereof exposed. Since the tip 20 bears against the bottom of the opening 32, the block acts as a backing member when the severed end of the catheter is forced over the head member 22 of the cannula selected for use.
In use and during the operation the surgeon will note the size of the artery exposed and to be catherized. He will then sever the tapered portion 14 of the catheter at the reference point which corresponds to the size of the artery. Since one of the cannulae 16 has an inside diameter that corresponds to the point at which the catheter was severed, the surgeon will then insert the severed end over the head member of the corresponding cannula without removing the cannula from the block 30. If necessary, the sutures 28 are applied and the assembled catheter and cannula are then removed from the block 30 and the cannula is inserted into the exposed artery. Since the inside diameter of the thin-walled cannula 16 is approximately the same as that of the exposed artery, and since the reduction of lumen size from cannula to catheter is negligible, the velocity of the stream will not be affected and hemolysis, turbulence and other deleterious effects on the blood are avoided.
The catheters embodied herein are relatively soft, providing some flexibility without kinking, and can be autoclaved without'any deleterious eitect thereon. The tapered design makes it possible to maintain an inventory of one type of catheter that can be adapted to a multiplicity of sizes. A constant nonturbulent flow against a constant back pressure is produced by using the combina tion of the catheter and cannula, and furthermore the combination of the tapered catheter and the thin-walled cannula makes possible the satisfactory solution of the hemodynamic or hydraulic problem of re-entry.
While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claim.
What is claimed:
In a surgical catheter, an elongated hollow body having a tapered portion formed on one end thereof, said hollow body being formed with a uniform inside diameter that extends a portion of the length thereof, the tapered portion of said body to the distal end thereof having an inside diameter of gradually decreasing diameter, a plurality of reference indicia marked on the outer surface of said tapered portion in spaced relation, said spaced reference indicia designating reference points that relate to the inside diameter of said tapered portion, said tapered portion being severable at :any of said reference indicia, so that the inside diameter of the distal end of said body as severed is formed in a predetermined dimension, and -a cannula termed of a metallic material and including a relatively thin-walled shank that terminates at one end thereof in an inclined edge, an enlarged head member joined to the other end of said shank and having an outer tapered surface that is secured to and inserted into the severed distal end of said tapered portion of said hollow body, the inside diameter of said cannula generally corresponding to the inside diameter of said tapered portion at the severed end thereof.
References Cited in the file of this patent UNITED STATES PATENTS 387,454 Siegenthaler Aug. 7, 1888 675,647 Andersen et a1 June 4, 1901 2,260,086 Matter Oct. 21, 1941 2,523,877 Pestolesi Sept. 26, 1950 2,550,132 Woods Apr. 24, 1951 2,638,897 Poitras May 19, 1953 2,857,915 Sheridan Oct. 28, 1958 2,952,861 Reggio Sept. 20, 1960 2,981,449 Perkins Apr. 25, 1961