Method and system for optimization of an exsanguination tourniquet

The exsanguination tourniquet includes a constricting member and at least one sleeve removably coupled to the constricting member. The system includes the exsanguination tourniquet and an applicator device. The method of assembling includes obtaining a constricting member, obtaining at least one sleeve, and wrapping the at least one sleeve around the constricting member.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is related to U.S. patent application Ser. No. 14/282,980 entitled “METHOD AND SYSTEM FOR OPTIMIZATION OF AN EXSANGUINATION TOURNIQUET” and PCT Application No. PCT/IL2014/050499 entitled “METHOD AND SYSTEM FOR OPTIMIZATION OF AN EXSANGUINATION TOURNIQUET” filed on the date of filing of the present application, which are incorporated herein by reference in their entirety.

FIELD OF INVENTION

This invention relates to the field of healthcare of humans and non-human mammals, and more specifically to the modification of blood flow in a limb.

BACKGROUND

Creation of a blood free surgical field during orthopedic, vascular and plastic surgery has been the standard of care for over 100 years. The initial device was described by Friederich August von Esmarch in 1873 and is still being used today as the Esmarch bandage. In 1908, Dr. Harvey Cushing first described the use of a pneumatic tourniquet to occlude the blood flow into the scalp during brain surgery. Combination of an Esmarch bandage for squeezing the blood away from a limb (exsanguination) and a pneumatic tourniquet to occlude arterial blood flow is currently used in over 90% of limb operations. The use of a pneumatic tourniquet to occlude the arterial blood flow into a limb is associated with a number of side effects and adverse reactions. The side effects and adverse reactions may include tourniquet paralysis, which is transient or permanent nerve damage caused by the mechanical affect of the wide tourniquet cuff on the nerve. (Ochoa at el. Anatomical changes in peripheral nerves compressed by a pneumatic tourniquet. J Anat. 1972; 113(Pt 3):433-55.) In addition, side effects and adverse reactions may include skin lesions, which are skin abrasions or liquid blisters at the site of tourniquet placements (tourniquet burn) and tourniquet pain, which is tenderness at the site where the tourniquet was placed, that may last for days or even weeks.

More recently devices combining the exsanguination effect of the Esmarch and the blood flow blocking of a tourniquet are being used. This new class of devices is called exsanguination tourniquets. This new technology not only acts as a tourniquet, but is also capable of shifting blood from one part of the limb to another or to the central circulation. Exsanguination tourniquets are described in details in U.S. Pat. Nos. 4,848,324 and 7,854,748 which are included herewith as reference. An important aspect of an exsanguination tourniquet is the need to maintain the pressure applied to the limb in a safe range to avoid crush injuries to the tissues beneath it at any point along the limb. At the same time, it is also critical that the pressure applied by the exsanguination tourniquet is sufficient in order to block the arterial blood flow into the limb.

SUMMARY OF INVENTION

Shortcoming of the prior art are overcome and additional advantages are provided through the provision of a method for determining at least one parameter of at least one component used to construct a safe and effective exsanguination tourniquet. The method includes: obtaining, by a processor, at least one parameter related to a material comprising the exsanguination tourniquet; obtaining, by the processor, at least one parameter related to the positioning of the exsanguination tourniquet on a given limb; obtaining, by the processor, identifying information comprising a description of at least one component of the exsanguination tourniquet; based on the identifying information, selecting program instructions for execution by the processor, wherein the program instructions comprise a relationship between a compressive pressure of the at least one component of the exsanguination tourniquet, the at least one parameter related to the material comprising the exsanguination tourniquet, and the at least one parameter related to the positioning of the exsanguination tourniquet, wherein the program instructions are stored on a computer readable storage medium; determining, by the processor, a compressive pressure of the exsanguination tourniquet by executing the selected program instructions; and determining, by the processor, if the compressive pressure of the exsanguination tourniquet is optimized by comparing the compressive pressure to one or more predefined values, wherein the one or more predefined values are stored on a computer readable storage medium.

Computer systems, computer program products and methods relating to one or more aspects of the technique are also described and may be claimed herein. Further, services relating to one or more aspects of the technique are also described and may be claimed herein.

In another aspect, an exsanguination tourniquet is provided which includes, for instance: a constricting member and at least one sleeve removably coupled to the constricting member.

In yet another aspect, an exsanguination tourniquet system is provided which includes, for instance: a constricting member; at least one sleeve removably coupled to the constricting member; and an applicator device.

In a further aspect, a method of assembling an exsanguination tourniquet is provided which includes, for instance: obtaining a constricting member; obtaining at least one sleeve; and wrapping the at least one sleeve around the constricting member.

Additional features are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered part of the claimed invention. For example, embodiments of the present invention utilize one parameter related to a material comprising an exsanguination tourniquet that is obtained from a tensile test machine communicatively coupled to the processor via a network connection, one parameter related to a component that is an elastic ring, one parameter related to the positioning of the exsanguination tourniquet on the given limb relative to the end of an extremity on the limb, and verifying the compressive pressure of the exsanguination tourniquet.

DETAILED DESCRIPTION OF THE INVENTION

The computer system, method, and computer program product disclosed herein address the challenge of determining one or more parameters and/or dimensions for an exsanguination tourniquet, that can be applied to a limb in a safe range to avoid crush injuries to the tissues beneath it at any point along the limb, but also apply pressure sufficient to block the arterial blood flow into the limb.

Specific challenges addressed by aspects of the present technique include, but are not limited to, determining parameters for an exsanguination tourniquet for foot and ankle applications, determining parameters for an exsanguination tourniquet for forearm applications, determining parameters for an exsanguination tourniquet for oversize thick leg applications, and determining parameters for an exsanguination tourniquet for grossly oversize thick leg applications.

In an aspect of the present technique, an embodiment of the present invention obtains properties of the materials used to construct an exsanguination tourniquet, and/or the physical dimensions of the exsanguination tourniquet, and/or the placement of the exsanguination tourniquet when in use to determine at least one parameter that can be utilized to design at least one exsanguination tourniquet, adapted for one or more specific applications.

In another aspect of the present technique, an embodiment of the present invention obtains properties of the materials used to construct an exsanguination tourniquet, and/or the physical dimensions of the exsanguination tourniquet, and/or the placement of the exsanguination tourniquet when in use to verify the efficacy of at least one exsanguination tourniquet, adapted for one or more specific applications.

In another aspect of the present invention, properties of the materials used to construct an exsanguination tourniquet, and/or the physical dimensions of the exsanguination tourniquet, and/or the placement of the exsanguination tourniquet when in use, are utilized to monitor the pressure of the tourniquet to maintain a uniform pressure profile across the site to which the exsanguination tourniquet is applied. As understood by one of skill in the art, a pressure profile is uniform when at any point the pressure is no more than 20% more or less than the average value of the pressure profile.

FIG. 1is a computer system100configured to perform at least one aspect of an embodiment of the present invention. In the embodiment ofFIG. 1, software10is executed by at least one processor on a computer, termed a base computer12inFIG. 1for clarity. The terms software, program code, computer program code, code, computer program product, and executable instructions, are used interchangeably throughout this application.

The software comprises code that is accessible to the processor and executable by at least one processor of the computer12. The software can be stored on a memory on the physical computer12, and/or in a memory and/or on removable media accessible to the computer12via a network connection, including but not limited to, a wireless and/or wireless network, utilizing a protocol known to one of skill in the art. The computer may also be configured to act as a web server, which may be capable of running the software and hosting and/or interacting with the database14.

The base computer12, as well as any other computer described in the present specification can include personal computers, servers, smart phones, mobile devices, laptops, desktops, and/or any means of personal or corporate computing device capable of executing the software10or portions of the software10, or communicating with a computer executing the software10over a wireless or hard wired network.

In the embodiment ofFIG. 1, the base computer is connected to a computer network16, including but not limited to private and publicly accessible wired and wireless networks, and the Internet. In this embodiment, one or more computers, termed auxiliary computers18a-18care communicatively connected to the computer12via a computer network16, including but not limited to, the Internet. The auxiliary computer18a-18creceive data from the computer12, via, for example, the web server on the computer12and the auxiliary computers18a-18ccan render (for viewing) determinations of parameters served by the base computer12, and the base computer can obtain data from the auxiliary computers18a-18c, including but not limited to, properties of the materials used to construct an exsanguination tourniquet, and the physical dimensions of the limb(s) to which an exsanguination tourniquet is to be applied.

The base computer12in the embodiment ofFIG. 1includes a database14. Additional embodiments of the present invention utilize databases and other memory devices in different physical locations that are remotely accessible to the base computer12executing the software10. In the embodiment ofFIG. 1, the database14stores data regarding the properties of the materials used to construct an exsanguination tourniquet, as well as data related to various parameters affecting the utilization of embodiments of the technique.

FIG. 2illustrates a block diagram of a resource200in computer system100, such as base computer12and auxiliary computers18a-18c, which is part of the technical architecture of certain embodiments of the technique. Returning toFIG. 2, the resource200may include a circuitry202that may in certain embodiments include a microprocessor204. The computer system200may also include a memory206(e.g., a volatile memory device), and storage208. The storage208may include a non-volatile memory device (e.g., EEPROM, ROM, PROM, RAM, DRAM, SRAM, flash, firmware, programmable logic, etc.), magnetic disk drive, optical disk drive, tape drive, etc. The storage208may comprise an internal storage device, an attached storage device and/or a network accessible storage device. The system200may include a program logic210including code212that may be loaded into the memory206and executed by the microprocessor204or circuitry202.

In certain embodiments, the program logic210including code212may be stored in the storage208, or memory206. In certain other embodiments, the program logic210may be implemented in the circuitry202. Therefore, whileFIG. 2shows the program logic210separately from the other elements, the program logic210may be implemented in the memory206and/or the circuitry202.

Using the processing resources of a resource200to execute software, computer-readable code or instructions, does not limit where this code can be stored. Referring toFIG. 3, in one example, a computer program product300includes, for instance, one or more non-transitory computer readable storage media302to store computer readable program code means or logic304thereon to provide and facilitate one or more aspects of the technique.

Referring toFIG. 4, in an embodiment of the present invention, a tensile test device can be communicatively coupled to a resource200, such as that inFIGS. 1-2, for verifying mechanical properties of materials that can be processed utilizing software10executed by at least one processor in a computer system, such as resource200, to determine the efficacy of an existing tourniquet and/or determine characteristics, such as ranges of pressure, that enable the effective design of additional exsanguination tourniquets. Aspects of this embodiment and methods for verifying the efficacy of an exsanguination tourniquet in accordance with the present technique will be discussed in greater detail later.

Referring toFIGS. 5A-5B, in an embodiment of the present invention, one or more tools500for verifying the pressure generated by a tourniquet can be communicatively coupled to a resource200, such as that inFIGS. 1-2, for verifying the pressure generated by the tourniquet, which can be processed utilizing software10executed by at least one processor in a computer system, such as resource200, to determine the efficacy of the tourniquet.FIG. 5Ais a schematic view of a pressure measurement device for verifying the pressure generated by a tourniquet when applied to a limb model, whileFIG. 5Bis a schematic cross sectional view of a pressure measurement device for verifying the pressure generated by a tourniquet when applied to a limb model. Aspects of this embodiment and methods for verifying the efficacy of an exsanguination tourniquet in accordance with the present technique will be discussed in greater detail later.

As will be appreciated by one skilled in the art, aspects of the technique may be embodied as a system, method or computer program product. Accordingly, aspects of the technique may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system”. Furthermore, aspects of the technique may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus or device.

These computer program instructions, also referred to as software, such as the software10inFIG. 1, may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

In one aspect of the technique, an application may be deployed for performing one or more aspects of the technique. As one example, the deploying of an application comprises providing computer infrastructure operable to perform one or more aspects of the technique.

As a further aspect of the technique, a computing infrastructure may be deployed comprising integrating computer readable code into a computing system, in which the code in combination with the computing system is capable of performing one or more aspects of the technique.

As yet a further aspect of the technique, a process for integrating computing infrastructure comprising integrating computer readable code into a computer system may be provided. The computer system comprises a computer readable medium, in which the computer medium comprises one or more aspects of the technique. The code in combination with the computer system is capable of performing one or more aspects of the technique.

Further, other types of computing environments can benefit from one or more aspects of the technique. As an example, an environment may include an emulator (e.g., software or other emulation mechanisms), in which a particular architecture (including, for instance, instruction execution, architected functions, such as address translation, and architected registers) or a subset thereof is emulated (e.g., on a native computer system having a processor and memory). In such an environment, one or more emulation functions of the emulator can implement one or more aspects of the technique, even though a computer executing the emulator may have a different architecture than the capabilities being emulated. As one example, in emulation mode, the specific instruction or operation being emulated is decoded, and an appropriate emulation function is built to implement the individual instruction or operation.

FIG. 6shows a cross section of an exsanguination tourniquet40. The exsanguination tourniquet40issued as U.S. Pat. No. 7,854,748 which is herein incorporated by reference in its entirety. The other half of the exsanguination tourniquet40may be generally symmetrical to the portion shown inFIG. 6. The exsanguination tourniquet40may be constructed from an elastomeric ring2and may include an elastic sleeve4coupled to a plurality of straps6and wrapped around the elastomeric ring2. The straps6may include at least one handle8. As seen inFIG. 6, in general, an exsanguination tourniquet consists of at least one elastic ring which is wrapped around by an elastic sleeve.

Exsanguination tourniquets can be constructed in varying configurations and from a variety of materials. In general, an exsanguination tourniquet includes an elastic ring, which an elastic sleeve is wrapped around, as seen inFIG. 6, and described in greater detail above. However, some embodiments of the exsanguination tourniquets of the present invention include a constricting ring comprised of a flexible material, including but not limited to, steel. A constricting device in the exsanguination tourniquet can also include one or more concentric metallic springs, as described in greater detail below. In one example, a plurality of metallic springs are placed one inside the other to create the constricting portion of the exsanguination tourniquet. Given that limbs to which the exsanguination tourniquets are applied are not always uniform in circumference, some embodiments of the exsanguination tourniquets include an elastic ring and a non-uniform elastic sleeve, for example, a non-uniform sleeve with a conical shape. However, regardless of the materials that comprise the exsanguination tourniquet, aspects of the present technique enable optimization of the pressure level in order to achieve a uniform pressure profile over the length of the application site.

FIG. 7is an exemplary workflow700of the present invention that can be performed by a computer system, such as that inFIG. 1, utilizing resources, such as that inFIG. 2. For ease of understanding, the process ofFIG. 7is framed in the context of the system ofFIG. 1, with reference toFIGS. 4 and 5.

Embodiments of the present invention can be utilized both to develop parameters that can be utilized in an exsanguination tourniquet to achieve the requisite pressure to operate efficiently and can also evaluate an existing exsanguination tourniquet to determine whether the desired pressure can be achieved given the properties of the exsanguination tourniquet and the application thereof. The workflow700ofFIG. 7utilizes aspects of an embodiment of the present invention to determine the pressure applied by a given exsanguination tourniquet in order to evaluate the efficacy of this exsanguination tourniquet.

An embodiment of the present technique can be used to determine whether an exsanguination tourniquet is being applied to a given site in an effective manner, but in order to make this determination, an embodiment of the technique first determines the pressure that is applied by a given exsanguination tourniquet at the given site. As aforementioned, embodiments of the present technique determine whether the pressure applied over the entire site to which the exsanguination tourniquet is applied is within an effective (predetermined) range as well as whether that pressure profile is uniform across the application site, e.g., a limb.

Referring toFIG. 7, the software10executed on one or more processors of a computer system obtains descriptive parameters710including, but not limited to, characteristics of the exsanguination tourniquet, including but not limited to, parameters related to the materials that comprise the given exsanguination tourniquet and physical dimensions of the exsanguination tourniquet. In embodiments of the present invention, parameters utilized by the software10vary in accordance with the composition of the exsanguination tourniquet.

When obtaining parameters related to a given exsanguination tourniquet, some embodiments of the present invention do not utilize values related to all components of the exsanguination tourniquet. For example, the software10can make a determination regarding whether the pressure in a given exsanguination tourniquet is consistent with maintaining a uniform pressure profile throughout and within an effective range by evaluating parameters related to one or more components of the exsanguination tourniquet, and/or all the combined components. Embodiments of the present invention can be utilized to determine the efficacy of a given exsanguination tourniquet based upon components, including but not limited to, an elastic ring, a spiral spring, a plurality of concentric spiral metallic springs, a combination of an elastic ring and elastic cylinder, and an elastic ring and at least one non-uniform elastic sleeve.

Alternatively, certain embodiments of the present technique can utilize parameters related to all elements of an exsanguination tourniquet to determine its efficacy. One embodiment of the present invention obtains parameters related to a plurality of tension generating circular elements and a plurality of sleeves of different parameters.

Parameters related to the exsanguination tourniquet obtained by the software10in various embodiments of the present technique vary depending upon the design and/or components of the exsanguination tourniquet. For example, for a tourniquet comprised of an elastic ring, parameters include, but are not limited to, the internal diameter of the ring before stretching it, the thickness of the ring before stretching it, the elastic constant of the ring from Hooke's law, and/or the thickness of the ring in the stretched mode at a desired distance from the tips of the toes or the fingers. For a constricting ring including a spiral spring made of steel or similar flexible material that is a component of an exsanguination tourniquet, parameters obtained by the software10include, but are not limited to, the wire diameter of the spring, the mean diameter of the spring before stretching it, the number of active coils in the spring, and/or the mean diameter of the spring in the stretched mode at a desired distance from the tips of the toes or the fingers. When obtaining the parameters of an exsanguination tourniquet that includes concentric spiral metallic springs, parameters include, but are not limited to, the wire diameter of the spring, the mean diameter of spring before stretching it, the number of active coils in spring, and/or the mean diameter of spring in the stretched mode when applied at a given distance from the tips of the toes or the fingers of a wearer. For an exsanguination tourniquet comprising an elastic ring and elastic cylinder, in an embodiment when parameters are obtained by the software10relating to both components, parameters obtained related to the elastic cylinder include, but are not limited to, the length of the elastic cylinder, the width of the elastic cylinder before stretching it, the thickness of the cylinder wall, the radial elastic constant of the elastic cylinder (from Hooke's law), and/or the contribution of the elastic cylinder to the thickness of the device in the stretched mode at a given distance from the tips of the toes or the fingers.

In addition to obtaining parameter information related to the exsanguination tourniquet, the software10also obtains information related to the positioning of the exsanguination tourniquet on a given limb720. In embodiments of the present invention, the software10obtains the distance of the position of the exsanguination tourniquet on the limb relative to the tips of the toes or the fingers, depending upon the limb upon which the exsanguination tourniquet is placed and/or the limb circumference at this position.

In embodiments of the present invention, the software10executed on one or more processors of a computer resource obtains the descriptive parameters related to the exsanguination tourniquet and/or the placement data by communicating with external tools that are coupled to a computer resource that is accessible to a processor executing the software10, over a communications network. These tools include, but are not limited to a tensile verification tool, such as that inFIG. 4.

FIG. 4is a tensile test machine400, which is a tool that is used, in embodiments of the present invention, for obtaining parameters related to tensile characteristics of the materials that comprise exsanguination tourniquets and the components of the exsanguination tourniquet, for example, an elastic ring, elastic spring, elastic sleeve, and/or the assembled tourniquet. The tool is utilized in embodiments of the present invention to verify the mechanical properties of these components. The tensile test machine400is an example of a device known in the art that can be utilized to obtain and/or verify the mechanical properties of elements comprising exsanguination tourniquets, as well as the assembled tourniquet. One of skill in the art will recognize that other known methods of evaluating these properties can be implemented and communicatively coupled to a computer resource accessible to software10executed by a processor to practice aspects of the disclosed technique.

In embodiments of the present invention, the tensile test machine400is used for testing a specimen3while being held on the upper hook5and the lower hook7. The mobile base11of the upper hook5enables stretching of the specimen. The control panel9of the tensile test machine400is communicatively coupled to a computer resource accessible to the software10. To obtain parameters related to the materials and components of the exsanguination tourniquet, the processor executes software10that instructs the tensile test machine to apply a known force to a component of an exsanguination tourniquet, and/or to set a specific elongation for a component of the exsanguination tourniquet. While the specimen is stretched by the tensile test machine400, enabled by the software10, the calibrated unit13measures both force and elongation. Since the pressure generated by any element/component is determined by its mechanical properties, the tensile test machine enables the software10to determine several parameters from the tensile test, including but not limited to K, the elastic constant of the component.

In further embodiments of the present invention, one or more of these parameters are entered via a user interface into a computer resource of the computer system practicing aspects of the technique.

In another embodiment of the present invention, one or more of the parameters utilized by the present invention are obtained by the software10from a memory device, such as a database, communicatively accessible to the one or more processors executing the software10.

Returning toFIG. 7, in addition to obtaining descriptive parameters710and information related to the positioning of the exsanguination tourniquet on a given limb720, the software10also obtains a description of the one or more components of the exsanguination tourniquet730to be used in determining the compressive pressure of the exsanguination tourniquet. As aforementioned, embodiments of the present invention can determine the compressive pressure of a given exsanguination tourniquet based on one or more of the components that comprise the exsanguination tourniquet. The software10obtains this information from a resource accessible to the computer resource executing the software10, including but not limited to, inputs by a user through an input device on a computer resource accessible to the software10via a network connection, including but not limited to inputs into a specialized tool, such as those inFIGS. 4-5, and/or a standard input device known to one of skill in the art. In embodiments of the present invention, this information includes whether the exsanguination tourniquet includes one or more of the following components: an elastic ring, a spiral spring, a spiral metallic spring, an elastic cylinder, a non-uniform elastic sleeve, a circular element. In the embodiment ofFIG. 7, the description obtained730can include both the identification of one or more components and the number of each of the identified components. For example, a given exsanguination tourniquet may contain more than one circular element and/or more than one elastic sleeve.

Once the software10obtains a description of the one or more components of the exsanguination tourniquet730, the software10selects computer instructions (computer code) wherein the computer instructions comprise instructions for determining the compressive pressure of the exsanguination tourniquet740. For ease of understanding, these instructions are represented throughout this specification as mathematical formulas (equations). These equations represent the relationship of the compressive pressure of an exsanguination tourniquet relative to various parameters obtained by the software10. In embodiments of the present invention, the computer program selected by the software and subsequently executed by a processing resource in the computer system practicing the technique can be embodied in a stored procedure, a code fragment, a plain text file, etc., or any similar medium known to one of skill in the art and accessible by executing software10, in various embodiments of the present invention.

The software10utilizes the selected program and the obtained parameters to determine the compressive pressure generated by a given exsanguination tourniquet750. In general most cases, an exsanguination tourniquet consists of an elastic ring which is wrapped around by an elastic cylinder. For any specific limb of a circumference CLimb(x) at a position that is a distance XLimbfrom the tips of the toes or the fingers with a desired minimum compressive pressure PMinand a maximum compressive pressure PMax, the software10utilizes a method represented by Equation 1 to calculate of the pressure generated by an elastic ring, when an elastic ring is identified as a component.

In Equation 1:

x=a position on the limb that is located at a distance XLimbfrom the tips of the toes or the fingers.

C(x)=the limb circumference at position x.

DRing=the internal diameter of the ring before stretching it.

dRing=the thickness of the ring before stretching it.

KRing=the elastic constant of the ring from Hooke's law.

dRing(x)=the thickness of the ring in the stretched mode at a distance XLimbfrom the tips of the toes or the fingers, calculated using the Poisson's ratio of the ring.

This elastic ring, when stretched, generates circumferential force and radial pressure that can be determined by the software10.

In an embodiment of the present invention, the software10selects and utilizes a method represented by Equation 2 when determining the pressure generated by a constricting ring consisting of a spiral spring made of steel or similar flexible material.

In Equation 2:

x=a position on the limb that is located at a distance XLimbfrom the tips of the toes or the fingers.

dsp=the wire diameter of the spring.

Dsp=the mean diameter of the spring before stretching it.

nsp=the number of active coils in the spring.

Dsp(x)=the mean diameter of the spring in the stretched mode at a distance XLimbfrom the tips of the toes or the fingers, corrected for effect of elongation on Dsp.

In an embodiment of the present invention, the software10selects and utilizes a method represented by Equation 3 when determining the compressive pressure of an exsanguination tourniquet comprising concentric spiral metallic springs. This component includes a plurality of concentric spiral metallic springs that are placed one inside the other.

In Equation 3:

x=a position on the limb that is located at a distance XLimbfrom the tips of the toes or the fingers.

dspi=the wire diameter of spring i.

Dspi=the mean diameter of spring i before stretching it.

nspi=the number of active coils in spring i.

Dspi(x)=the mean diameter of spring i in the stretched mode at a distance XLimbfrom the tips of the toes or the fingers, corrected for effect of elongation on Dspi.

In Equation 3, above, i goes from 1 to M, and M designates the properties of the external-most-spring.

An exsanguination tourniquet can comprise an elastic ring and an elastic cylinder, for example, an elastic constricting ring wrapped around by an elastic cylindrical sleeve comprises such an exsanguination tourniquet. In this case, in an embodiment of the present invention, the software10selects and applied a method represented by Equation 4 to calculate the compressive pressure.

The parameters for the ring are described in relation to Equation 1, but in Equation 4 for the elastic cylinder are as follows:

x=a position on the limb that is located at a distance XLimbfrom the tips of the toes or the fingers.

LCyl=the length of the elastic cylinder.

WCyl=the width of the elastic cylinder before stretching it.

KCyl=the thickness of the cylinder wall.

KCyl=the radial elastic constant of the elastic cylinder from Hooke's law.

N(x)=the contribution of the elastic cylinder to the thickness of the device in the stretched mode at a distance XLimbfrom the tips of the toes or the fingers.

FIG. 8is a graph showing the pressure generated by an elastic ring wrapped around by an elastic cylindrical sleeve, when applied to a uniform diameter cylinder.FIG. 9shows the pressure when the elastic ring wrapped around by the elastic sleeve is applied over a conical shaped member from its narrower end (X=0) to its wider end (X=100 [cm]).

By selecting and applying a method embodied by a formula, the software10determines the compressive pressure. Returning toFIG. 7, once the software determines the compressive pressure, the software10evaluates whether the compressive pressure is optimized, i.e., whether the pressure is relatively uniform over the entire length of the conical limb as shown inFIG. 9.

In an embodiment of the present technique, designs produced by the technique are based on one or more of the following constraints: 1) the linear stretching range of the elastic elements (ring, sleeve and spring); 2) the thickness of the device shall be at least 15 [mm] (or 25[mm] in case of a grossly thick limb) at all times; 3) the ring dimensions (thickness and internal diameter) shall enable its rolling on the limb; 4) both the Young's modulus of the elastic elements and the thickness of the sleeve are limited due to production constraints; 5) the pressure profile exerted by the device shall be within the range of 150-350 [mm Hg] and shall be uniform—all values shall be within the range of ±20% that of the average pressure of the profile; 6) the elastic constant (K) of the spring is limited up to 0.05 [kg/mm] due to the mechanical properties of steel; 7) the maximal values of the following parameters are limited due to cost considerations: DRing, LCyl, WCyl, dsp, Dspand nsp.

In an aspect of this embodiment, the constraints ensure that the design will be effective. For example, the pressure profile, in an exemplary exsanguination tourniquet wherein at least one parameter was determined by the present technique, is within the range of 150-350 [mmHg]. A pressure lower than 150 [mmHg] is less effective because it may not occlude the arterial blood flow, and a pressure greater than 350 [mmHg] is less effective because it may cause tissue injuries.FIG. 10is a graph showing the pressure profile exerted by two designs of a foot and ankle device.

Referring toFIG. 10, the higher line on the graph is an effective design produced by the present technique as, with a pressure profile within the range of 150-350 [mmHg]. The lower line inFIG. 10represents an ineffective design, as the sleeve of the tourniquet associated with this parameter is too wide.FIG. 10demonstrates that the pressure of the non-effective design is below 150 [mmHg] along most of the limb and that utilizing this parameter in an exsanguination tourniquet may cause the tourniquet to fail.

An exsanguination tourniquet may also comprise an elastic ring and a non-uniform elastic sleeve. An embodiment of an invention applies the method in Equation 5 to determine the pressure applied by an elastic ring wrapped around by an elastic sleeve that has a non-uniform conical shape.

The majority of the parameters of Equation 5 are defined in Equation 4, for the elastic sleeve of Equation 5: WCyl(x)=the width of the elastic sleeve before stretching it at a distance XLimbfrom the distal end of the limb.

As discussed earlier, a standard exsanguination tourniquet is comprised of one to a plurality of tension generating circular elements and one to a plurality of sleeves, in which the sleeves are optionally of different parameters. Upon receiving descriptive information indicating this configuration via an input, including but not limited to, a selection through a user interface, or a reading from a tool configured to communicated with a computer resource of a system practicing aspects of the method, the software10utilizes the method of Equation 6 below to determine the compressive pressure of the exsanguination tourniquet.

In Equation 6, “M” defines the number of circular elements and “N” defined the number of circular sleeves.

For M circular elements:

x=a position on the limb that is located at a distance XLimbfrom the tips of the toes or the fingers.

=the internal diameter of the circular element j before stretching it.

dj=the thickness of the circular element j before stretching it.

Kj=the elastic constant of the circular element j from Hooke's law.

dj(x)=the thickness of the circular element j in the stretched mode at a distance XLimbfrom the distal end of the limb, calculated using the Poisson's ratio of the circular element.

For N elastic sleeves:

x=a position on the limb that is located at a distance XLimbfrom the tips of the toes or the fingers.

L=the length of sleeve i.

Wi(x)=the width of sleeve i before stretching it at a distance XLimbfrom the distal end of the limb.

Hi(x)=the thickness of sleeve i wall at a distance XLimbfrom the distal end of the limb.

Ki=the radial elastic constant of sleeve i from Hooke's law.

Ni(x)=the contribution of sleeve i to the thickness of the device in the stretched mode at a distance XLimbfrom the distal end of the limb.

In addition to providing parameters related to the mechanical properties of the elements, as well as the assembled tourniquet, herein disclosed are validation methods and devices for verifying and validating that a design of any exsanguination tourniquet, developed based on the unified equations and range of parameters disclosed in Table 1 below, meets the required specifications. These devices and methods can be divided into 2 groups:

1. Tools and methods for verifying the mechanical properties of the elements, as well as the assembled tourniquet.

2. Tools and methods for validating the pressure generated by an exsanguination tourniquet when applied to a limb-shaped simulator.

FIG. 7described aspects of an embodiment of the technique when utilized to determine whether the compressive pressure of a given exsanguination tourniquet is optimal. However, embodiments of the present invention can also be utilized to assist in designing exsanguination tourniquets in accordance with the anatomical properties of an application site and the known optimal compressive pressure. Additionally, one of skill in the art will understand that the method can be utilized to locate an optimal application site given parameters describing the materials utilized in a given exsanguination tourniquet and the desired compressive pressure. To this end, an embodiment of the present technique was utilized to generate Table 1, shown below, which exhibits a range of values for each of the parameters for a number of specific anatomical dimensions of limbs. It is understood that one of skill in the art could utilize the present technique to determine other parameter value combinations for the examples below, as well as other limb dimensions.

Referring to Table 1, for the elastic ring, the following parameters are provided:

DRing=the internal diameter of the ring before stretching it.

dRing=the thickness of the ring before stretching it.

ERing=the Young's modulus of the ring.

Referring to Table 1, for the elastic sleeve:

LCyl=the length of the sleeve.

WCyl=the width of the sleeve before stretching it.

HCyl=the thickness of the sleeve wall.

ECyl=the Young's modulus of the sleeve.

Referring to Table 1, for the elastic spring:

dsp=the wire diameter of the spring.

Dsp=the mean diameter of the spring before stretching it.

nsp=the number of active coils in the spring.

Table 2 below represents the anatomical dimensions of the limbs referred to in Table 1.

Referring to Table 1, in an embodiment of the present technique, the range of values for the parameters in Table 1 is bounded based on one or more of the following constraints: 1) the linear stretching range of the elastic elements (ring, sleeve and spring); 2) the thickness of the device shall be at least 15 [mm] (or 25 [mm] in case of a grossly thick limb) at all times; 3) the ring dimensions (thickness and internal diameter) shall enable its rolling on the limb; 4) both the Young's modulus of the elastic elements and the thickness of the sleeve are limited due to production constraints; 5) the pressure profile exerted by the device shall be within the range of 150-350 [mm Hg] and shall be uniform—all values shall be within the range of ±20% that of the average pressure of the profile; 6) the elastic constant (K) of the spring is limited up to 0.05 [kg/mm] due to the mechanical properties of steel; 7) the maximal values of the following parameters are limited due to cost considerations: DRing, LCyl, WCyl, dsp, Dspand nsp.

The effect of stretching the ring beyond initial circumference (C0) for a given set of parameter values taken from Table 1 as applied to a limb geometry taken from Table 2 is shown inFIG. 11, where the X-axis is the distance starting from X=0 at the tips of the toes or the fingers in centimeters, and the Y-axis is the pressure in mm Hg at each location. As explained previously, the efficacy of an exsanguination tourniquet relies, in some part, upon the exsanguination tourniquet applying a nearly uniform compressive pressure across an application site, such as a limb.

Returning toFIG. 7, after the compressive pressure for a given exsanguination tourniquet application to a specific area is determined, the software10executed by a processor can verify that the pressure is accurate760. In embodiments of the present invention, pressure measurements from an exsanguination tourniquet are obtained from a pressure measurement device500such as the device inFIGS. 5A-5B. Measurements from this tool can be utilized by the software10in systems to verify the pressure determined by the software10based on the parameters obtained and/or to verify the efficacy of an exsanguination tourniquet designed utilizing embodiments of the present invention.

Referring toFIGS. 5A-5B, a pressure measurement device500utilized in an embodiment of the present invention includes a limb model21(also called a limb simulator) that consists of several layers23for modeling different depths inside the limb. Each layer is covered along the simulated limb by an array of pressure sensors25, which are sampled by a sensor measurement device27connected to a computer resource in an embodiment of the present invention. The pressure measurement device500is an example of a device known in the art that can be utilized to obtain and/or verify the pressure generated by an exsanguination tourniquet when applied to a limb-shaped simulator. One of skill in the art will recognize that other known methods of pressure on a limb simulator can be implemented and communicatively coupled to a computer resource accessible to software10executed by a processor to practice aspects of the disclosed technique.

While the tourniquet29is applied to the limb the generated pressure is measured according to the selected sensor (the selected depth).FIG. 5B, to which reference is now made, shows a cross-section of the limb model21. The layers23of different depths are covered by the pressure sensors25which measure the pressure generated when the tourniquet29is applied to the simulated limb model. In the center of the limb model there is a rigid rod30, which simulates a bone inside the limb. It is clear that by selecting different materials and dimensions it is possible to create different limb models, varying by shape, depths levels and stiffness.

An example of the pressure measurement results as shown in the software is shown inFIG. 12to which reference is now made. The chart41shows the pressure distribution along the limb in the selected depth (according to the selected pressure sensor). The baseline pressure43is related to the limb's area which is unaffected by the tourniquet, while the peak pressure45is related to the limb's area affected by the constricting tourniquet. These results enable the validation of important parameters, such as: average pressure, peak pressure, total pressure and the area influenced by the tourniquet, which are critical for the validation of the unified equations described above.

Utilizing embodiments of the technique of the present invention, software10executed by a processor, can determine new designs and configurations for exsanguination tourniquets, based upon the compressive pressure and the parameters discussed related to the materials and characteristic of the materials that comprise the tourniquet as well as the characteristics of the site (limb) to which the newly determined configurations for exsanguination tourniquets will be applied. Embodiments of the present invention were utilized to produce exsanguination tourniquets that are optimized to accommodate the following sites: the foot and ankle, the forearm, an oversize thick leg, a grossly oversize thick leg. The following exsanguination tourniquets configurations determined utilizing aspects of embodiments of the present technique are offered as examples. One of skill in the art will recognize that the methods disclosed can be adapted to determine configurations for exsanguination tourniquets adapted to any and all application sites on a body, irrespective of the location of the site and any individual characteristics of the site.

An embodiment of the present technique was utilized to determine an original design for a ring and two sleeves exsanguination tourniquet for foot and ankle. An embodiment of the present technique was used to determine an original design for an exsanguination tourniquet comprising a ring and two sleeves for use on a forearm. An embodiment of the present invention was utilized to determine an exsanguination tourniquet configuration (design) for an oversize thick leg comprising a spring and two sleeves. An embodiment of the present invention was also utilized to determine a configuration for an exsanguination tourniquet for grossly oversize thick leg and the resultant exsanguination tourniquet comprises two springs and two sleeves.

The aforementioned exsanguination tourniquet including a ring and two sleeves adapted for the foot and ankle includes an elastic ring wrapped around by two elastic sleeves.

Table 3 below contains the parameters for this exsanguination tourniquet, derived utilizing an embodiment of the present invention.FIG. 13is a graph depicting the pressure generated by this exsanguination tourniquet, when applied to a conical shaped limb from its narrower end to its wider end (from an initial circumference of 20 [cm] to a final circumference of 40 [cm] over a length of 60 [cm]).

An embodiment of the present technique was utilized to determine an original design for a ring and two sleeved exsanguination tourniquet for a forearm. The resultant exsanguination tourniquet comprises an elastic ring wrapped around by two sleeves adapted for use on the forearm, the parameters of which are listed in Table 4.FIG. 14is a graph depicting the pressure generated by such exsanguination tourniquet when applied to a conical shaped limb from its narrower end to its wider end (from an initial circumference of 10 [cm] to a final circumference of 35 [cm] over a length of 35 [cm]).

An embodiment of the present technique was utilized to determine an original design for an exsanguination tourniquet for an oversize thick leg. Table 2 defines the dimensions of an oversize thick leg. The resultant exsanguination tourniquet comprises a spring and two sleeves. The elastic ring in this device consists of a spiral spring made of steel and wrapped around by two sleeves. The parameters of this device are shown in Table 5.FIG. 15shows the pressure generated by such exsanguination tourniquet when applied to a conical shaped limb from its narrower end to its wider end (from an initial circumference of 25 [cm] to a final circumference of 85 [cm] over a length of 100 [cm]).

FIG. 16shows a cross-section of an embodiment of an exsanguination tourniquet61including a plurality of coiled concentric spring members67,69and at least one sleeve65. The device is applied to a limb63, for example, a conical shaped limb, and consists of an internal spring member69placed inside an external spring member67which is wrapped around by at least one sleeve65. The at least one sleeve65may be, for example, two elastic cylindrical sleeves. The two elastic cylindrical sleeves65may partially overlap both while wrapped around the constricting member67,69and when deployed onto the patient's limb63. In addition, although not shown, it is also contemplated that the exsanguination tourniquet61may include at least one strap and at least one handle on the strap for deploying the exsanguination tourniquet61on the patient's limb63. The at least one strap and at least one handle may be of the type shown inFIG. 6and described in greater detail above, in U.S. Pat. No. 7,854,748 and International Application No. PCT/IL2013/050563, each of which is herein incorporated by reference in their entireties. Further, the exsanguination tourniquet61may be used with an applicator device, such as applicator device170, as described in greater detail below.

A configuration for an exsanguination tourniquet, as seen inFIG. 16may be utilized for placement of a grossly oversize thick leg, as defined by the parameters to Table 2. An embodiment of the present invention is utilized to determine this design wherein the constricting member in this device consists of, for example, two spiral concentric spring members made of a flexible metal such as steel, placed one inside the other and wrapped around by two sleeves. Exemplary parameters determined by an embodiment of the present invention for this exsanguination tourniquet are listed in Table 6.FIG. 17is a graph that depicts the pressure generated by this exsanguination tourniquet when applied to a conical shaped limb from its narrower end to its wider end (from an initial circumference of 25 [cm] to a final circumference of 120 [cm] over a length of 100 [cm]).

FIGS. 18-19depict different views of an embodiment of an exsanguination tourniquet180utilizing the aforementioned two sleeve configuration and can be utilized on a foot, ankle, leg, and forearm, as described above. The exsanguination tourniquet180may include a constricting member182and at least one sleeve186,188. The exsanguination tourniquet180may also include an applicator device170. The applicator device170may be of the type disclosed in International Application No. PCT/IL2013/050563, which is incorporated herein by reference in its entirety. In the depicted embodiment, the at least one sleeve186,188may be wrapped around the constricting member182, as shown inFIG. 18. Then the at least one sleeve186,188may optionally be applied over the applicator device170as the exsanguination tourniquet180is deployed over the patient's limb, as shown inFIG. 18. Further, the exsanguination tourniquet180may include at least one strap (not shown) secured to the constricting member182to assist with placing the exsanguination tourniquet180onto the patient. The at least one strap (not shown) may also include at least one handle (not shown) to assist with placing the exsanguination tourniquet180onto the patient's limb. The at least one strap and at least one handle may be of the type shown inFIG. 6and described in greater detail above and in U.S. Pat. No. 7,854,748 and PCT/IL2013/050563, each of which is incorporated herein by reference in their entireties.

The at least one sleeve186,188may be, for example, a single sleeve (not shown) or multiple overlapping sleeves, such as, a first sleeve186and a second sleeve188which overlap in region184. Additional numbers of sleeves are also contemplated as would be understood by one of ordinary skill in the art to cover larger or longer limbs. As depicted inFIGS. 18-19, the at least one sleeve includes a first sleeve186which may be, for example, a distal sleeve, and a second sleeve188which may be, for example, a proximal sleeve. The sleeves186,188may be separate sleeves which overlap in the region184, although it is also contemplated that the sleeves186,188may be coupled or secured together in the region184to create a single sleeve. The sleeves186,188may overlap by, for example, approximately 3-5 [cm], although other amounts of overlap are also contemplated depending on the parameters required for excluding blood from the patient's limb. An exsanguination tourniquet180with multiple independent sleeves186,188, which overlap during deployment onto a patient, enables easy removal of the first sleeve186after deployment is complete to expose the surgical site or field, while keeping the second sleeve188on the patient's limb.

The constricting member182may be, for example, a generally ring-shaped member that enables the at least one sleeve186,188to couple to the constricting member182for deploying the exsanguination tourniquet180onto a patient's limb. The constricting member182may have, for example, a generally circular cross-section to enable easier rolling of the exsanguination tourniquet180onto the patient's limb. The constricting member182may be, for example, an elastic ring or at least one spring member. The elastic ring may be, for example, an elastic member, such as a silicon ring or ring made of another elastic material as known by one of ordinary skill in the art which can expand and contract. The at least one spring member may be, for example, at least one ring shaped spring member which may be a coiled spring that forms a ring.

In embodiments which use multiple spring members, the spring members may each be, for example, coiled spring members that each form a ring and the spring members may be fit inside of each other. For example, as shown inFIG. 21, a first spring member2001may be positioned inside of a second spring member2003. The first and second spring members2001,2003may have, for example, a generally circular cross-section to enable easier rolling of the exsanguination tourniquet2000onto the patient's limb. The first spring member2001may be, for example, an internal spring member and it is contemplated that multiple internal spring members may be used to obtain the desired pressure on the patient's limb to exclude blood from the patient's limb while the exsanguination tourniquet2000is deployed. The exsanguination tourniquet2000, ofFIG. 21, may also include at least one sleeve2005. The second spring member2003may be, for example, an external spring member and the at least one sleeve2005may be wrapped around the second spring member2003.

FIG. 20depicts a two spring member embodiment of an exsanguination tourniquet190. A cross-section of the exsanguination tourniquet190is shown after being deployed on the patient's limb196. As shown inFIG. 20, a first spring member194may be positioned inside the second spring member192. To enable the first spring member194to be positioned inside of the second spring member192, the outer diameter of the first spring member194will be smaller than the inner diameter of the second spring member192. The first spring member194may include a plurality of coils and each coil is represented by two dots inFIG. 20. Likewise, the second spring member192may include a plurality of coils and each coil is represented by two dots inFIG. 20. The first and second spring members194,192may have, for example, a generally circular cross-section to enable easier rolling of the exsanguination tourniquet190onto the patient's limb. As the exsanguination tourniquet190is deployed on the patient's limb196both spring members192,194may apply a force on the limb196to exclude blood out of the patient's limb196. As the spring members192,194are deployed onto the patient's limb196, the spring members192,194stretch radially and the distance between the coils increases. As depicted inFIG. 20, as the exsanguination tourniquet190is deployed onto the patient's limb196the distance between the coils of the external circumference of each spring member192,194is larger than the distance between the coils of the internal circumference of each spring member192,194which contact the patient's limb. In addition, as the exsanguination tourniquet190is rolled over the patient's limb196, at least one sleeve, such as sleeve198, is deployed onto the patient's limb196to maintain pressure on the limb196and restrict blood flow to the patient's limb196. The sleeve198may be wrapped around the spring members192,194prior to being rolled out onto the patient's limb196. The spring members used in the exsanguination tourniquets190,2000may include a plurality of coils and the number of coils is dependent upon the desired properties of the spring member, as described in greater detail above with reference to Table 1. In addition, the number of coils in each spring member will be dependent upon the dimensions of the patient's limb.

The exsanguination tourniquet embodiments ofFIGS. 20-21may also include at least one strap (not shown) secured to the external spring members192,2003of the constricting members to assist with placing the exsanguination tourniquets190,2000onto the patient. The at least one strap (not shown) may also include at least one handle (not shown) to assist with placing the exsanguination tourniquet190,2000onto the patient's limb. The at least one strap and at least one handle may be of the type shown inFIG. 6and described in greater detail above and in U.S. Pat. No. 7,854,748 and PCT/IL2013/050563, each of which is incorporated herein by reference in their entireties. In addition, the at least one sleeve198,2005may optionally be applied over the applicator device170, as described in greater detail above, as the exsanguination tourniquet190,2000is deployed over the patient's limb.

The exsanguination tourniquets61,180,190,2000, as shown inFIGS. 16 and 18-21, may be used on a patient's limbs, for example, a patient's foot, ankle, leg, hand, wrist, and arm. The exsanguination tourniquets61,180,190,2000may include a constricting member, for example, an elastic ring182or at least one spring member67,69,192,194or2001,2003, and at least two sleeves65,186,188,198,2005. The elastic ring182and the at least one spring member67,69,192,194or2001,2003may be formed to exert a desired tension force on to the patient's limb. The tension forces of the elastic ring182and/or the at least one spring member67,69,192,194or2001,2003are determined by the dimensions, materials, and mechanical properties of the elastic ring182and/or the at least one spring member67,69,192,194,2001,2003. Where there are at least two springs, such as in the embodiments ofFIGS. 16, 20, and 21each spring may have a different dimension so that they may fit inside of each other, may each be made of the same or different material, and may each have the same or different material properties. Based on the desired pressure profile, an elastic ring182, at least one spring member67,69,192,194or2001,2003, or any combination thereof may be selected with the dimensions, materials, and mechanical properties necessary to achieve the desired pressure profile, which may be determined as described in greater detail above with reference toFIGS. 1-17. Also as described in greater detail above, the exsanguination tourniquets61,180,190,2000may be formed with the desired parameters based on the materials used and the number of constricting members and sleeves used to exclude a patient's blood from their limb without causing tissue damage. For example, the at least one spring member67,69,192,194,2001,2003may be made of a metal, such as, stainless steel, and the elastic ring182may be made of silicone or another elastic material. At least one spring member67,69,192,194or2001,2003may be used instead of an elastic ring182for the constricting member to reduce costs and make it easier for the surgeon to roll the constricting member over the patient's limb in order to exclude the patient's blood. Although not shown, it is also contemplated that an elastic ring may be positioned inside at least one spring member to form yet another embodiment exsanguination tourniquet.

The exsanguination tourniquets61,180,190,2000may be made based on the parameters discussed above with reference toFIGS. 8-17and which will not be described again here for brevity sake. The parameters may be used to optimize the blood exclusion from a patient's limbs using the exsanguination tourniquets180,190,2000. Exclusion may include both exsanguination or removing the blood from the patient's limb and arterial occlusion or preventing the re-entry of blood into the limb.