METHOD FOR PREVENTING AIR EMBOLISM IN A SYRINGE FOR ANGIOGRAPHIC POWER INJECTOR
United States Patent 3752145
A power injector or syringe designed for use in angiographic studies having a cylindrical, hollow housing and a plunger or piston fitted for reciprocating action within the housing. The housing is provided with a transparent, magnifying conical-shaped head for more easily detecting air bubbles entrained in a liquid contained by the syringe. Detection of these bubbles prior to injection minimizes the chances of air embolism during intravenous injections.
US Patent References:
METHOD AND APPARATUS FOR INJECTING FLUID INTO THE VASCULAR SYSTEM
Hobbs - January 1972 - 3631847
Injection syringe
Gidlund - October 1967 - 3349767
Administration set
Thornton, Jr. - April 1962 - 3030954
Magnifying attachment for syringes
Tschischeck - February 1952 - 2586581
METHOD AND APPARATUS FOR INJECTING FLUID INTO THE VASCULAR SYSTEM
Hobbs - January 1972 - 3631847
Injection syringe
Gidlund - October 1967 - 3349767
Administration set
Thornton, Jr. - April 1962 - 3030954
Magnifying attachment for syringes
Tschischeck - February 1952 - 2586581
Inventors:
Runnells, Robert R. (Fruit Heights, UT)
Longson, Frank W. (Salt Lake City, UT)
Longson, Frank W. (Salt Lake City, UT)
Application Number:
05/194747
Publication Date:
08/14/1973
Filing Date:
11/01/1971
View Patent Images:
Export Citation:
Assignee:
MDT Instrument Company (Salt Lake City, UT)
Primary Class:
Other Classes:
604/155, 604/122
International Classes:
A61B6/00; A61M5/178; A61M5/31; A61M5/18; A61B5/02
Field of Search:
128/218R,218C,221,218N,2R,215,216,214C,218A,2.5R,2.5F,2S
Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Mcgowan J. C.
Claims:
We claim
1. In angiography wherein contrast solution is poured into the housing of a power injector syringe and thereafter expelled at a controlled rate by power means advancing the plunger of said syringe towards the outlet thereof, the improvement for eliminating the hazard of air embolism resulting from expelling entrapped air from said syringe into the vascular system of a patient comprising:
2. The improvement of claim 1 wherein the contrast solution is poured into said syringe from the outlet end with the said magnifying head removed.
3. The improvement of claim 1 including attaching a tube to said outlet;
1. In angiography wherein contrast solution is poured into the housing of a power injector syringe and thereafter expelled at a controlled rate by power means advancing the plunger of said syringe towards the outlet thereof, the improvement for eliminating the hazard of air embolism resulting from expelling entrapped air from said syringe into the vascular system of a patient comprising:
2. The improvement of claim 1 wherein the contrast solution is poured into said syringe from the outlet end with the said magnifying head removed.
3. The improvement of claim 1 including attaching a tube to said outlet;
Description:
Background of the Invention
1. Field
This invention relates to a liquid injector, and particularly to a power syringe or injector designed for use in angiographic studies.
2. State of the Art
Angiography is generally defined as the visual roentgenological study of blood vessels. As the definition implies, a dye or contrast fluid is continuously injected into an artery or vein until the fluid is distributed throughout the vascular system. X-rays are then taken, permitting the vascular system (because of the opaque quality of the dye) to be clearly outlined. Defects, constrictions, etc. of the vascular system can thereby be easily detected. The inadvertent introduction of air during transportation of the contrast fluid into the vascular system can result in air embolism.
Power injectors are commonly used in angiographic studies. Normally, such an injector includes a syringe with a cylindrical hollow housing having an outlet at one end and a piston or plunger mounted slidably within the housing and capable of removal from the end of the housing opposite the outlet. Contrast fluid is poured into the syringe housing opening with the plunger removed. The plunger is controllably moved within the housing by a power means, typically, a hydraulic drive mechanism. The housing and power means are usually held in predetermined stationary position by an adjustable support means (the "syringe arm housing" of the injector). A catheter is conventionally connected to the syringe housing's outlet, and a contrast fluid is forced through the catheter into a vascular system. Heretofore, angiographic techniques relying upon power injectors have exposed the patient to an undesirably high risk of air embolism, because of the difficulty of determining whether air is entrapped within the syringe.
Summary of the Invention
The present invention provides an improved angiographic syringe specifically adapted for use in conventional angiographic power injectors. The syringe of this invention comprises a special magnifying head at the outlet end of the syringe housing which facilitates the discovery of entrapped air. The head is also specially contoured within to provide a safety chamber which, in cooperation with stop means, prevents the expulsion of a certain quantity of the contrast fluid from the syringe.
Brief Description of the Drawings
The drawing, which illustrates what is presently regarded as the best mode for carrying out the invention, is a perspective view of the angiographic syringe of this invention with sections cut away for clarification.
Description of the Illustrated Embodiment
The syringe of this invention includes a cylindrical, hollow housing 12 and a plunger or piston plate 14 match-fitted within the housing for slidable action. By providing an outside wall diameter of the piston plate 14 fractionally smaller than the inner wall diameter of the cylindrical housing 12, substantially no liquid escapes from between the walls under normal use. However, to insure a tight circumferential fit between the inner wall of the housing and the outer wall of the plunger (yet not overly restricting reciprocating action of the plunger), O-rings 16 are inserted into grooves 18 cut along the outer wall of the plunger. The sealing action of these O-rings insures a tight fit against the inner wall of the housing, particularly if the inner housing wall happens to be irregular.
A threaded shaft 20 is attached to the piston plate 14 and extends up beyond the cylindrical housing 12, even when fully advanced toward the outlet 22 of the housing 12. The shaft 20 may be either permanently or detachably fastened to the piston plate 14. As shown, one end 20a of the shaft 20 is screwed into a corresponding threaded central opening 24 of the piston plate 14. The other end 20b of the shaft 20 may be connected to the drive mechanism of a power injector by any suitable means (not shown). The central portion 20c of the shaft 20 engages a threaded cental opening 30 of a circular stop plate 32 having a diameter larger than the inner diameter of the syringe housing 12. The stop plate 32 may be positioned at any desired location along the shaft 20 to check the advance of the piston plate 14 (by contact with the upper edge 34 of the syringe housing 12) as the shaft 20 is pushed down through the syringe housing 12. In this fashion, a predetermined quantity of contrast fluid, as selected by proper positioning of the stop plate, but no more, is injected into the vascular system of the patient.
In most angiographic studies the amount and rate of fluid introduced into the vascular system by the syringe must be carefully controlled. The upper portion 36 of the syringe housing 12 is threaded for mounting within the syringe arm housing (not shown) of conventional power injectors. When so mounted, the upper end 20b of shaft 20 is connected as described hereinbefore to a drive system capable of moving the shaft and piston plate 14 through the housing at a preselected controlled speed, thereby insuring a constant and continuous flow of a contrast fluid from the syringe into the vascular system.
At the outlet end of the syringe housing 12 is a novel syringe head 40 manufactured from a transparent material which is molded and/or machined to achieve magnification sufficient to facilitate viewing of the fluid contained therewithin. The syringe head 40 is preferably conically shaped--that is, the walls 42 of the syringe head converge in and down toward a centraly located outlet 22. A catheter (not shown) may be connected to the outlet 22 by means of a coupling means, such as the luer lock catheter coupling 44 illustrated, for carrying fluid from the syringe and into the vascular system.
The interior 46 of the magnifying head 40 provides a safety chamber which captures and retains a residual portion of the contrast dye or other fluid even when the piston plate 14 is fully advanced toward the outlet 22. Further advance of the piston plate 14 is checked by a stop surface 48 defined in part by the upper edge 40a of the head 40. It is thus physically impossible to expel all of the fluid contained by the syringe housing 12 through the outlet 22 by merely advancing the piston plate 14. This feature, together with the magnification provided by the head 40, makes it possible to virtually assure that no air will be injected into a patient from the claimed syringe.
The procedure normally followed in using the claimed syringe is to first position the syringe housing with the outlet end up and the magnification head 40 removed. Contrast solution is poured into the syringe housing and the head 40 is replaced. A tube is then attached to the outlet 22 of the syringe and the free end of the tube is submerged in contrast solution. Air is bled from the syringe by advancing the piston plate 14 toward the outlet 22. Additional contrast solution may then be drawn through the tube into the syringe housing by retracting the piston plate. The contents of the safety chamber 46 may then be viewed through the transparent wall 42 of the magnifying safety head. If bubbles are noted, the piston plate is advanced and retracted once more to expel the entrapped air and to replace the desired volume of contrast solution. The contents of the safety chamber are again viewed, and the piston plate may again be advanced and retracted as often as necessary until no bubbles are observed through the magnifying walls 42 of the head 40.
Sometimes it is convenient to eliminate the step of filling the syringe housing through the tip end, but in any event, the presence of entrapped air is determined by visual observation with the magnifying head up and the syringe as nearly vertical as possible, and after all observed air is expelled, injections should be given with the outlet down and the syringe as nearly vertical as the angiographic procedure permits.
The piston plate is advanced in accordance with the program of the angiographic procedure, but the piston plate can never advance beyond the stop surface 48 of the magnifying head 40. Any entrapped air will tend to rise in the contrast solution toward the piston plate. Accordingly, it will be retained within the safety chamber 46.
Although in most cases the housing is constructed from a metal such as stainless steel, durable plastic may also be used. The syringe head, although normally totally transparent, may be constructed from an opaque material such as plastic or metal and magnifying windows inserted into the head to permit internal viewing.
For most angiographic work the solution introduced into the patient should be maintained at a controlled temperature, e.g., a temperature approaching body temperature. The claimed syringe is compatible with the heating jackets (not shown) contained within the syringe arm housings of available power injectors, but it is within contemplation that heating coils may be provided in the syringe housing 12 if desired.
The syringe head 40 is transparent and capable of magnification, but it must also have high resistance to breakage and be resistant to the conditions normally encountered in sterilization procedures. The magnifying power of the head should be substantially greater than is provided by the glass walls of a conventional medical syringe, for example. Thus, the surfaces of the walls 42 should be contoured to increase the magnification provided by the shape of a conventional syringe tip. Transparent polycarbonate resin, such as that marketed by the General Electric Company under the Trademark "LEXAN," is the presently preferred material of construction, but certain other plastic and resin materials have suitable properties for use.
Reference herein to details of the illustrated embodiment is not intended to restrict the scope of the claims which themselves recite the features regarded as essential to the invention.
1. Field
This invention relates to a liquid injector, and particularly to a power syringe or injector designed for use in angiographic studies.
2. State of the Art
Angiography is generally defined as the visual roentgenological study of blood vessels. As the definition implies, a dye or contrast fluid is continuously injected into an artery or vein until the fluid is distributed throughout the vascular system. X-rays are then taken, permitting the vascular system (because of the opaque quality of the dye) to be clearly outlined. Defects, constrictions, etc. of the vascular system can thereby be easily detected. The inadvertent introduction of air during transportation of the contrast fluid into the vascular system can result in air embolism.
Power injectors are commonly used in angiographic studies. Normally, such an injector includes a syringe with a cylindrical hollow housing having an outlet at one end and a piston or plunger mounted slidably within the housing and capable of removal from the end of the housing opposite the outlet. Contrast fluid is poured into the syringe housing opening with the plunger removed. The plunger is controllably moved within the housing by a power means, typically, a hydraulic drive mechanism. The housing and power means are usually held in predetermined stationary position by an adjustable support means (the "syringe arm housing" of the injector). A catheter is conventionally connected to the syringe housing's outlet, and a contrast fluid is forced through the catheter into a vascular system. Heretofore, angiographic techniques relying upon power injectors have exposed the patient to an undesirably high risk of air embolism, because of the difficulty of determining whether air is entrapped within the syringe.
Summary of the Invention
The present invention provides an improved angiographic syringe specifically adapted for use in conventional angiographic power injectors. The syringe of this invention comprises a special magnifying head at the outlet end of the syringe housing which facilitates the discovery of entrapped air. The head is also specially contoured within to provide a safety chamber which, in cooperation with stop means, prevents the expulsion of a certain quantity of the contrast fluid from the syringe.
Brief Description of the Drawings
The drawing, which illustrates what is presently regarded as the best mode for carrying out the invention, is a perspective view of the angiographic syringe of this invention with sections cut away for clarification.
Description of the Illustrated Embodiment
The syringe of this invention includes a cylindrical, hollow housing 12 and a plunger or piston plate 14 match-fitted within the housing for slidable action. By providing an outside wall diameter of the piston plate 14 fractionally smaller than the inner wall diameter of the cylindrical housing 12, substantially no liquid escapes from between the walls under normal use. However, to insure a tight circumferential fit between the inner wall of the housing and the outer wall of the plunger (yet not overly restricting reciprocating action of the plunger), O-rings 16 are inserted into grooves 18 cut along the outer wall of the plunger. The sealing action of these O-rings insures a tight fit against the inner wall of the housing, particularly if the inner housing wall happens to be irregular.
A threaded shaft 20 is attached to the piston plate 14 and extends up beyond the cylindrical housing 12, even when fully advanced toward the outlet 22 of the housing 12. The shaft 20 may be either permanently or detachably fastened to the piston plate 14. As shown, one end 20a of the shaft 20 is screwed into a corresponding threaded central opening 24 of the piston plate 14. The other end 20b of the shaft 20 may be connected to the drive mechanism of a power injector by any suitable means (not shown). The central portion 20c of the shaft 20 engages a threaded cental opening 30 of a circular stop plate 32 having a diameter larger than the inner diameter of the syringe housing 12. The stop plate 32 may be positioned at any desired location along the shaft 20 to check the advance of the piston plate 14 (by contact with the upper edge 34 of the syringe housing 12) as the shaft 20 is pushed down through the syringe housing 12. In this fashion, a predetermined quantity of contrast fluid, as selected by proper positioning of the stop plate, but no more, is injected into the vascular system of the patient.
In most angiographic studies the amount and rate of fluid introduced into the vascular system by the syringe must be carefully controlled. The upper portion 36 of the syringe housing 12 is threaded for mounting within the syringe arm housing (not shown) of conventional power injectors. When so mounted, the upper end 20b of shaft 20 is connected as described hereinbefore to a drive system capable of moving the shaft and piston plate 14 through the housing at a preselected controlled speed, thereby insuring a constant and continuous flow of a contrast fluid from the syringe into the vascular system.
At the outlet end of the syringe housing 12 is a novel syringe head 40 manufactured from a transparent material which is molded and/or machined to achieve magnification sufficient to facilitate viewing of the fluid contained therewithin. The syringe head 40 is preferably conically shaped--that is, the walls 42 of the syringe head converge in and down toward a centraly located outlet 22. A catheter (not shown) may be connected to the outlet 22 by means of a coupling means, such as the luer lock catheter coupling 44 illustrated, for carrying fluid from the syringe and into the vascular system.
The interior 46 of the magnifying head 40 provides a safety chamber which captures and retains a residual portion of the contrast dye or other fluid even when the piston plate 14 is fully advanced toward the outlet 22. Further advance of the piston plate 14 is checked by a stop surface 48 defined in part by the upper edge 40a of the head 40. It is thus physically impossible to expel all of the fluid contained by the syringe housing 12 through the outlet 22 by merely advancing the piston plate 14. This feature, together with the magnification provided by the head 40, makes it possible to virtually assure that no air will be injected into a patient from the claimed syringe.
The procedure normally followed in using the claimed syringe is to first position the syringe housing with the outlet end up and the magnification head 40 removed. Contrast solution is poured into the syringe housing and the head 40 is replaced. A tube is then attached to the outlet 22 of the syringe and the free end of the tube is submerged in contrast solution. Air is bled from the syringe by advancing the piston plate 14 toward the outlet 22. Additional contrast solution may then be drawn through the tube into the syringe housing by retracting the piston plate. The contents of the safety chamber 46 may then be viewed through the transparent wall 42 of the magnifying safety head. If bubbles are noted, the piston plate is advanced and retracted once more to expel the entrapped air and to replace the desired volume of contrast solution. The contents of the safety chamber are again viewed, and the piston plate may again be advanced and retracted as often as necessary until no bubbles are observed through the magnifying walls 42 of the head 40.
Sometimes it is convenient to eliminate the step of filling the syringe housing through the tip end, but in any event, the presence of entrapped air is determined by visual observation with the magnifying head up and the syringe as nearly vertical as possible, and after all observed air is expelled, injections should be given with the outlet down and the syringe as nearly vertical as the angiographic procedure permits.
The piston plate is advanced in accordance with the program of the angiographic procedure, but the piston plate can never advance beyond the stop surface 48 of the magnifying head 40. Any entrapped air will tend to rise in the contrast solution toward the piston plate. Accordingly, it will be retained within the safety chamber 46.
Although in most cases the housing is constructed from a metal such as stainless steel, durable plastic may also be used. The syringe head, although normally totally transparent, may be constructed from an opaque material such as plastic or metal and magnifying windows inserted into the head to permit internal viewing.
For most angiographic work the solution introduced into the patient should be maintained at a controlled temperature, e.g., a temperature approaching body temperature. The claimed syringe is compatible with the heating jackets (not shown) contained within the syringe arm housings of available power injectors, but it is within contemplation that heating coils may be provided in the syringe housing 12 if desired.
The syringe head 40 is transparent and capable of magnification, but it must also have high resistance to breakage and be resistant to the conditions normally encountered in sterilization procedures. The magnifying power of the head should be substantially greater than is provided by the glass walls of a conventional medical syringe, for example. Thus, the surfaces of the walls 42 should be contoured to increase the magnification provided by the shape of a conventional syringe tip. Transparent polycarbonate resin, such as that marketed by the General Electric Company under the Trademark "LEXAN," is the presently preferred material of construction, but certain other plastic and resin materials have suitable properties for use.
Reference herein to details of the illustrated embodiment is not intended to restrict the scope of the claims which themselves recite the features regarded as essential to the invention.