Heat Generating Tourniquet for Venipuncture Applications

1. Field of the Invention

The present invention concerns medical tourniquet devices for stabilizing and/or for inducing vasodilation of human veins in support of the venipuncture of or intravenous insertions into such veins.

2. Description of the Relevant Art

When in medical therapy or diagnosis it becomes necessary to puncture a human's blood vessel, nominally a vein, with a needle or syringe in order to inject medication, remove blood and/or make an intravenous connection, it is necessary to (i) locate a suitable vein and subsequently (ii) insert a needle through the skin (i.e. soft tissue) and into the interior of the vein. Sometimes during this procedure a suitable vein proves difficult to locate as well as often difficult to reliably insert the needle into its interior. Difficulties in location and/or insertion may exist because the walls of the patient's vein have degenerated at the site of venipuncture either from the effects of previous punctures because the patient is elderly or obese, and/or because the patient's vein is prone to roll from side to side. When a venipuncture is not reliably performed upon an initial attempt then it causes, at the minimum, additional discomfort and accumulative injury to the patient when the venipuncture is repeated. Unreliably performed venipuncture can also magnify and compound damage to the veins. Finally, unreliably performed venipuncture potentially results in poor intravenous connection for the collection of blood and/or the administration of therapeutic agents.

Devices for holding, stabilizing, constricting, immobilizing, and/or stimulating veins during medical venipuncture in order to aid the successful performance thereof are known in the prior art. U.S. Pat. No. 2,234,961 for a VEIN HOLDER to P. L. Canada shows a tourniquet in combination with a device for holding an adjacent vein against movement in order to facilitate intravenous injections and the like. The holding device comprises an arm of complex structure including a pressure member with fingers spaced to receive between them the vein which is to be punctured. Canada generally shows that a vein may be mechanically held not only against movement, but may also be held in high relief to aid medical personel in performing venipuncture.

U.S. Pat. No. 4,314,568 for VASCULAR STABILIZER to Loving shows an adjustable and disposable device maintained on a human appendage, and in pressured contact with the flesh about the location of a vein, by a strap. A living hinge portion connects two half body portions and permits a pivotal motion whereby ribs on each half-bodied portion may be brought together in parallel in order to stabilize a blood vessel lined between the ribs. A step locking mechanism prevents pivotal motion in a retrograde direction and thus ensures that the device is used for only a single venipuncture procedure, thereby preventing cross-contamination between patients. Loving generally shows that mechanical force may be used against the skin of a patient in order to draw a vein nearer to the surface of the skin.

U.S. Pat. No. 4,586,924 for VEIN CONSTRICTOR AND IMMOBILIZER for Lanning shows a device having a pressure plate which is hand held in pressured contact with the skin at the position of a vein. The planar pressure plate has in one of its ends a notch entirely through its thickness. At the apex of the notch a tapered groove is present within the bottom surface of the pressure plate. This tapered groove starts at the apex of the notch and terminates at the bottom surface of the pressure plate at a position intermediate the apex and the opposing edge of the pressure plate. When the groove and notch are both placed in pressured contact about the vein, they combinatorially constrict and immobilize the vein so as to allow venipuncture at the position of the notch. Lanning generally shows that veins may be mechanically constricted longitudinally, as well as laterally, along their length.

U.S. Pat. No. 4,316,461 for INTERVENOUS VASULAR STABILIZER to Marais, et al. discloses a method of performing venipuncture through a cutaway section within a central slot of a base plate, which slot overlays a vein. The slot is defined by an arched connector, or hood portion, which rigifies the slot and protects a needle-type catheder in its inserted positon. By exerting pressure on this connector, or hood, portion then the base is pressed downwardly on either side of the vein, which vein is then noticeably elevated into the slot area as well as being laterally stabilized. The pressure plate is held in position upon the human flesh and about the vein by straps. Marais, et al. generally shows that lateral pressure about a vein is useful for its mechanical stabilization during venipuncture.

Soft tissue in the area of veins may be mechanically manipulated other than in direct support of venipuncture. An example of the prior art showing mechanical manipulation of a vein at the site of venipuncture is contained within U.S. Pat. No. 3,620,209 for DEVICE FOR REDUCING THE PAIN OF INJECTIONS OF MEDICINES AND OTHER BILOGICALS to Kravitz. This patent shows a device which is held upon the skin, nominally by straps, and which vibrates the skin about the injection area. The vibration stimulates the pain center of the skin so that the pain of injections perceived by the patient may be minimized. Generally Kravitz indicates that stimuli, particularly taught to be mechanical stimuli, which is applied to the skin at or near the site of injection is potentially beneficial in mitigating or alleviating the patient's perception of pain associated with injection.

Also of relevance to the present invention is certain prior art concerned with the application of heated medical compresses to the skin, and the manner of generating heat externally or internally to such heated compresses. In this regard, U.S. Pat. No. 3,951,127 for CONSTANT TEMPERATURE DEVICE to Watson, et al., discloses a chemical heating device useable in medical applications. Specifically, a flexible container of a substantially planar configuration encloses a reservoir within which a first and second chemical may be combined in order to produce constant temperature heating. The resulting heated device is effected for use as a warm baby mattress, a warm blanket, or a hot water bottle substitute.

U.S. Pat. No. 3,463,161 for TEMPERATURE MAINTAINING DEVICE to Andrassy shows a flexible container containing a composition which is permanently plastic at temperatures throughout the range of zero degrees to one hundred and fifty degrees F. The container as well as its composition remains relatively soft and plastic during use. The container is generally divided into compartments by barriers and/or dividers. Andrassy generally shows that flexible containers which are useful in medical applications and which contain emulsions or dispersions may be readily fabricated.

U.S. Pat. No. 4,573,447 for CHEMICAL HEATER to Thrash, et al., discloses a chemical heater having a ruptureable container inside a substantially puncture- and rupture-proof envelope. After rupture of the inner container, heat is produced by exothermic reation. The particular chemical compositions, and the particular concentrations of chemicals within these compositions, which allow attainment of some desired exothermic reaction temperature are described.

The present invention is embodied in a disposable heat-generating tourniquet, and a method of using such a tourniquet in support of venipuncture or the making of intraveneous connections. The purpose of the tourniquet, and the method of its use, is to both (i) stabilize and (ii) vasodilate a vein which is subject to venipuncture. The stabilization is by mechanical means. The vein is stabilized by physically locking, or immobilizing, it within a window of a tourniquet pad portion of the device. The simultaneous vasodilation is both by mechanical means and also by thermal means. The vein is vasodilated, causing the vein to pressurize and swell, by subjecting it to (i) selective constriction and (ii) the application of heat by the same tourniquet pad portion in an area adjacent to the vein.

In one of its aspects, the disposible tourniquet in accordance with the present invention includes a pad portion which defines a substantially central window aperture. This pad portion, when pressured by a tourniquet strap portion against a patient's skin in a position about a vein, physically immobilizes and stabilizes this vein. Venipuncture may then be accomplished on that portion of the vein which is outlined within the tourniquet's window aperture without any attendant rolling or movement of the vein. This window aperture aspect of the present invention is, without more, efficacious in support of venipuncture.

In another of its aspects, the disposable tourniquet in accordance with the preent invention has a pad portion which is not of equal thickness. The pad portion of the tourniquet has a contour which initially increases in thickness radially from its window aperture. The tourniquet pad portion is also pliable and resilient, particularly because the pad portion preferably defines and contains one or more fluid reservoirs. The aperture window, the contours, and the flexible compliance of the pad portion are, without more, sufficient to cause the patient's skin and a portion of his vein to "puff up" through the window aperture. This puffing further facilitates locating, immobilizing, and stabilizing the vein for the purpose of venipuncture.

In still another of its aspects, the tourniquet in accordance with the present invention thermally induces vasodilation of the vein which it also immobilizes. Specifically, the pad portion of the tourniquet preferably defines a pair of storage reservoirs, preferably one reservoir within another. The reservoirs contain chemicals, preferably, but not necessarily limited to liquids, which are capable of producing an exothermic reaction upon mixing. A barrier which is located between the reservoirs, or which constitutes the wall of the inner reservoir, is frangible and may be manually ruptured, allowing he chemicals to mix. This mixing initiates an exothermic reaction of a temperature sufficient to induce vasodilation of that vein in the region about which the pad portion of the tourniquet is temporarily affixed, yet insufficient to cause damage, i.e. burn the soft tissue of the patient. This vasodilation swells and distends the vein, allowing it to further engorge with blood thereby enhancing venipuncture.

The tourniquet in accordance with the present invention further preferably includes a reusable tape tab for easy affixation to the limb of a patient. A frangible path, lined by a ripcord, is preferably provided between the window aperture and outer the periphery of the pad portion. Upon those instances that a butterfly intravenous needle, or other medical instrument is left inserted within a vein, then the tourniquet may readily be removed from about the medical instrument by fracturing, or ripping, along this predetermined frangible path. The tourniquet is preferably entirely disposable after use.

These and other aspects of the present invention will become increasing clear upon reference to the drawings wherein:

FIG. 1 is a perspective view showing the preferred embodiment heat generating tourniquet for venipuncture applications in accordance with the present invention.

FIG. 2 is a cross-sectional view, taken along aspect line 2--2 shown in FIG. 1, of the preferred embodiment tourniquet in accordance with the present invention.

FIG. 3 is a diagrammatic representation of the manner of actuating the exothermic reaction within the preferred embodiment tourniquet in accordance with the present invention.

FIG. 4 is a diagrammatic representation showing the manner of accomplishing venipuncture through the window aperture within the preferred embodiment tourniquet in accordance with the present invention.

FIG. 5 is a partial perspective view of the preferred embodiment tourniquet in accordance with the present invention particularly showing the ripcord by which a channel may be opened within the pad portion of the tourniquet from the pad edge to the window aperture.

The present invention is concerned with stabilizing, immobilizing, controlling blood flow through, physically squeezing into a "puffed up" position of prominence relative to the surrounding skin, and vasodilating human blood vessels all in support of the medical puncture of such vessels. Particularly, the present invention is concerned with (i) mechanically (including hydrodynamically) and (ii) thermally manipulating human veins is support of venipuncture, or the intravenous entrance of medical syringes and needles into such veins.

The present invention is embodied in a heat generating tourniquet, and the method for the use of such tourniquet. A preferred embodiment tourniquet in accordance with the present invention is generally shown in drawings FIGS. 1-5. Within drawing FIG. 1 the tourniquet 10 may be seen to generally include an elongate strap portion 16 which is preferably fabricated of a plastic material formed integrally with a pad portion 12 and tab portion 29. The integral tab portion or area 29 is preferably covered with an adhesive 30 which is applied to the tourniquet surface and covered by a removable plastic cover or slip sheet 28.

As illustrated in FIG. 4, the tourniquet 10 may readily be mounted upon a human appendage, illustrated by example to be arm 42. Tourniquet 10 is mounted by removing the cover sheet 28 from the pad area 29, wrapping the strap portion 16 tightly around the human appendage, and then pressing the strap portion 16 tightly into contact with adhesive 30 at an appropriate extension along such strap portion 16. The strap portion 16 is formed sufficiently long to encircle desired appendage, and may be trimmed to length with scissors as desired either before or after mounting. If the unused length of the strap portion 16 is not trimmed then it flops harmlessly, and does not interfere with venipuncture.

Returning to FIG. 1, the pad portion 12 of tourniquet 10 defines a substantially central window aperture 14. This window aperture 14 may be of various shapes, but is preferably a rectangle which is centrally and symetrically located within pad portion 12. Again referring to FIG. 4, two opposed edges of the window aperture 14 to pad portion 12 will normally lie transversely across a human blood vessel (which generally runs longitudinally along a human appendage) when the window aperture 14 is positioned about such a blood vessel during operational use of tourniquet 10. In accordance with the general constriction principle of a tourniquet, the tourniquet 10 will stop blood flow within the blood vessel or vein, illustrated by example in FIG. 4 to be a vein 44. With the tourniquet 10 in place, the pad portion 12 of the tourniquet 10 may optionally be momentarily lifted with the finger at the portion of pad 12 which is upstream to vein 44, which vein 44 the pad 12 otherwise partially encloses within window aperture 14. This optional, momentary, lifting allows blood to accumulate within the apertured portion of vein 44 under the hydrodynamic pressure of the body's normal circulatory system. A slight distension, or swelling, or vasodilation of the vein 44 within the region of window aperture 14 may thus be immediately obtained. The finger may be used to enhance this effect by poking, prodding, and massaging flesh and blood toward the window aperture 14.

Therefore, as one aspect with in accordance with the present invention, a tourniquet defines a window aperture within which a human blood vessel may be positioned. Medical puncture of the blood vessel may transpire while the blood vessel is stabilized within this aperture window. In this regard, the vein is stabilized within the window by opposite end portions of the pad portion 12 clamping or anchoring down opposite ends of the vein therebenath, thereby eliminating any rolling of the vein within the vicinity of the window aperture 14. Furthermore, this particular apertured geometry presents an immediate opportunity to manipulate the edge of the tourniquet pad and the underlying flesh at the region of the window aperture in order to both mechanically and hydrodynamically cause a portion of a blood vessel within the window aperture became prominent by being both "puffed up" and mechanically (hydrodynamically) vasodilated.

Still another aspect of the present invention concerns thermal vasodilation of the blood vessel otherwise held in position by the tourniquet. Returning to FIG. 2, it may be noted that pad portion 12 is formed by a pair of layers 17, 18 which define a first cavity or reservoir 20. This reservoir 20 preferably extends around the substantial portion of pad portion 12. An additional reservoir is located within pad portion 12. This reservoir may be at an independent location within pad 12 where it is separated from the first reservoir 20 by a frangible wall, or may preferably be, as illustrated in FIG. 2, a second reservoir 26 which is entirely contained within the first reservoir 20. This reservoir 26 is defined by and held in position by sheets or walls 22, 24.

In accordance with the present invention, the first reservoir 20 and the second reservoir 26 each independently and separately store a chemical, preferably a fluid, which is capable of producing an exothermic chemical reaction upon mixing with the chemical of the other reservoir. The boundary between reservoirs is frangible, and subject to being ruptured by hand manipulation. Particularly in the preferred embodiment, the walls of second reservoir 26 located entirely within first reservoir 20 may be ruptured by twisting or squeezing with the human hand 40 as illustrated in FIG. 3. The resulting mixing or commingling of the separate chemicals previously stored within first reservoir 20 and second reservoir 26 results within an exothermic chemical reaction. This exothermic reaction preferably produces temperatures in the range of 105 degrees F. to 107 degrees F. A number of chemicals, both dry and liquid, which permit the generation of a safe exothermic reaction in this particular temperature range are taught within those patents identified within the Background of the Invention section to this specification disclosure. The teachings of those patents regarding the generation of medically theraputic exothermic chemical reactions are incorporated herein by reference. A preferred exothermic reaction will produce and sustain a temperature in the indicated range for a time period in excess of three minutes, which allows adequate time for deployment and use of the tourniquet in accordance with the present invention.

When the tourniquet 10 in accordance with the present invention produces heat by a commingling of chemicals in order to produce an exothermic reaction, then the tourniquet 10 will be warm when applied to the human arm 42 in a position about the blood vessel 44. The heat provided by the tourniquet 10 will cause vasodilation of the blood vessel 44, including both dimensional and coloration changes which still further serve to make the blood vessel 44 prominent within the region of window aperture 14.

Therefore, in accordance with the present invention the blood vessel 44 is simultaneously stabilized, distended by internal hydrodynamic pressure, "puffed-up" above the surface of the surrounding skin and vasodilated, meaning widened or distended. Particularly by the synergistic combination of all this mechanical and thermal manipulation, the blood vessel 44, even if its walls are corroded and damaged, will be presented to needle or syringe 46 as best as is possible. So presented, the blood vessel 44 is more probable of being successfully medically punctured than would otherwise be the case.

In the event of venipuncture by a syringe for the withdrawal of blood from a vein, or upon the occasion of the injection of any blood vessel, then after a withdrawal of the needle, or syring, 46 the tourniquet 10 is left disposed upon the arm 42. The strap 16 may be peeled from contact with adhesive 30 on tab 29 and the entire tourniquet 10 may be summarily discarded. However, in those instances that a continuing, semi-permanent, intravenous connection to blood vessel 44 is desired, the present invention provides a means to enable removal of the tourniquet from the patient without disturbing the existing intervenous connection. This means is illustrated in FIG. 5 and comprises means for severing a portion of the pad portion 12 to enable the same to be manually spread and removed from the patient. This severance is facilitated by a frangible channel, fracturable joint, or severable line or the like formed in the pad portion 12. Particularly in accordance with the preferred embodiment tourniquet 10 of the present invention which is illustrated in FIG. 5, it is preferred that the body portion 12 should be capable of being ripped and severed along a channel or demarcation line 32. The severance of body portion 12 long this line is facilitated by rip cord 34. When the window aperture 14 to body portion 12 is so opened by pulling the rip cord, then the tourniquet 10 may readily be removed from its position about any medical apparatus which remains in position within blood vessel 44 (shown in FIG. 4).

The heat-generating tourniquet in accordance with the present invention has been seen to exhibit diverse mechanical and thermal aspects. Many of these aspects are seperate and severable, and could readily be recombined to produce alternative tourniquet structures by a practitioner in the design of medical appliances. For example, the tourniquet body itself could be substantially of the shape and cross section taught without incorporating any reservoirs, or any means of producing exothermic reaction. For example, a pad which generates heat, whether by exothermic reaction or otherwise, could be used to temporarily overlay the entire region normally occupied by pad portion 12, including the area of window aperture 14. Upon such time as the heat from this pad had produced sufficient vasodilation of the blood vessel held within the window aperture, then the heated pad could be removed and venipuncture could then be accomplished through the window aperture identically as it is accomplished within the preferred embodiment of the invention.

Because the synergistically interactive principles expressed within the present invention are readily capable of being realized, and combined, in diverse physical embodiments, the present invention should be interpreted broadly. Particularly, the invention should be interpreted in accordance with the language of the following claims, only, and not solely in accordance with that particular preferred embodiment tourniquet in which the present invention has been taught.