Patent Application
20220047273
This disclosure relates generally to tourniquets, and more particularly to windlasses of tourniquets.
A tourniquet is a constricting band placed around a limb and tightened to eliminate arterial flow past the device. Simply tying a constricting band or material tightly around a limb rarely provides enough pressure to occlude arterial flow. To stop bleeding requires a mechanical advantage, and to stop bleeding, tightening the constricting band or material is necessary. A windlass or twist stick is conventionally used to tighten the constricting band or material.
Arterial blood flow (from the heart to extremities) into a limb is usually at a high-pressure and requires high pressure deep in the limb to occlude or stop the arterial flow. Venous flow (from the extremity to the heart) is usually at a low pressure from the limb and returning the blood back to the heart and requires less pressure than arterial flow to stop flow of the blood.
Material wrapped tightly around a limb, but without a “twist stick” or windlass to apply mechanical tension to the material, is a venous (low pressure) constricting band at best. Although arterial flow still occurs when material is merely wrapped tightly around a limb, which moves blood into the injured limb, the venous system is occluded or mostly occluded and can't return blood to the body. The blood that is flowing past the material wrapping through the artery will flow into the limb and will exit the limb through the wound in the limb, and thus out of body, resulting in blood loss. For wounded patients, that is detrimental if not fatal, but for taking blood samples that is desirable, where the phlebotomist places a “venous constricting band” around an arm to occlude the venous system which engorges the veins in the limb, making it easier to draw blood from enlarged veins. Thus, tourniquets without windlasses are venous constricting bands because windlasses are necessary to prevent hemorrhaging through the wound.
Tourniquets should be removed as soon as safely possible. Having a tourniquet applied for more than 6 hours is associated with distal tissue loss. According to at least one authority a tourniquet that has been in place for more than six hours should be left in place until the patient arrives at a medical facility. The personnel at the medical facility need to know the amount of time that the tourniquet has been in place in determining their treatment. Thus, it is critical to record the time that a tourniquet is applied. Many tourniquets have a place designated to record the time applied. However, because tourniquets are typically applied in the field outside of medical facilities, often in combat, disasters, or other emergency situations, a writing instrument capable of writing on the tourniquets may not be readily available.
U.S. Pat. Pub 20190216471 by Strattner for a “Tourniquet Windlass Device” describes a pen that can be used as a tourniquet windlass. The pen cannot be used to record on the tourniquet the time that the tourniquet was applied, because the pen is the windlass. The device of U.S. Pat. Pub 20190216471 is not directed to solving the problem of writing the time when the tourniquet is applied. The device combines the functionality of a pen and a windlass to “render the device desirable for persons who need to balance the weight and cumbersomeness of carrying multiple devices with the need to have a minimum number of functionalities within the set of devices that they carry.”
U.S. Pat. Pub. No. 20180168663 of Hill for a “Windlass Tourniquet With Embedded Writing Implement” describes a writing instrument that screws into a windlass. The writing instrument has male threads that mate with female screws in a tourniquet windlass. Alternatively, the writing instrument may be snapped into place in the windlass.
U.S. Pat. Pub. No. 20160367262 to Burke et al. for a “Tourniquet and Windlass Assembly and Method” describes a marking device, a grease pencil, having a cap on one end, which cap screws into a windlass. The cap has male threads that mate with female screws in a tourniquet windlass.
The above-mentioned shortcomings, disadvantages and problems are addressed herein, which will be understood by reading and studying the following specification.
In one aspect, a tourniquet to restrict a flow of blood in a body part includes a windlass having a cavity into which a writing instrument can be inserted. The writing instrument can be used, for example, for recording the time that the tourniquet was applied. The writing instrument is maintained within the cavity by a non-localized friction fit rather than being threaded into the cavity or held by a detent that requires a large initial force to overcome. The frictional force is determined by the design and is not dependent on how the writing instrument was last inserted.
Apparatus, systems, and methods of varying scope are described herein. In addition to the aspects and advantages described in this summary, further aspects and advantages will become apparent by reference to the drawings and by reading the detailed description that follows.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific implementations which may be practiced. These implementations are described in sufficient detail to enable those skilled in the art to practice the implementations, and it is to be understood that other implementations may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the implementations. The following detailed description is, therefore, not to be taken in a limiting sense.
The detailed description is divided into three sections. In the first section, problems with the prior art are described. In the second section, apparatus of implementations are described. In the third section, implementations of methods are described. Finally, in the fourth section, a conclusion of the detailed description is provided.
The systems of Hill and Burke et al. retain the writing instrument in the windlass using threads. That is, the pen screws into the windlass. Unscrewing the tourniquet pens of Hill and Burke from the windlass requires manual dexterity and multiple application of fine motor skills, which can be difficult to achieve in combat or other stressful situations. It is known that stress reduces dexterity and fine motor skills. See, for example, T. Cuper “Modeling the Effects of Stress: An Approach to Training,” https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100012855.pdf, which states: “In the case of a combat medic, stress levels can be expected to be extremely high as the lives of both the medic and his comrades are at risk. In addition, the medic's performance requirements are complex, demanding both gross (e.g. running) and fine (e.g. applying a tourniquet, firing a weapon) motor skills as well as unaffected cognitive functioning. It is known that under stress, fine motor skills and dexterity can be greatly reduced.”
Moreover, the initial force to begin unscrewing the marking device varies with the torque applied when the marking device was last inserted. Tourniquets are typically applied to patients that are losing a great deal of blood, and the hands of the field medic or first aider are often slippery with blood. This can make it difficult to apply sufficient torque to unscrew the writing device from the windlass, particularly if the writing device was over torqued when it was last inserted.
A snap, such as described by Hill, requires a greater initial force to overcome the snap, which requires a tight user grip that may not be possible with the user's hand wet with blood and fine motor skills compromised by stress. Moreover, if the pen is inadvertently snagged by something in the environment, such as dense vegetation, the pen can move sufficiently far to overcome the snap. Once the localized snap force is overcome, there is nothing to prevent the pen from falling out of the windlass.
Tourniquets are typically used in the field, in conditions in which they are exposed to dirt, mud, and other contaminants. Such contaminates can clog threads and snaps, making it more difficult to remove the pen, especially under stressful conditions.
In this section, the particular apparatus of such an implementation are described by reference to a series of diagrams.
To apply the tourniquet 100 to the limb, the user simply wraps the tourniquet around the subject appendage, loops the first end 120 of the belt 102 through the buckle 112, pulls the tourniquet 100 reasonably tight.
A windlass 106 includes a slot 122 through passes to the inner strap 104 as seen in
As shown in
In one implementation, ridges 712 are parallel to the axis of shaft 620 and evenly spaced circumferentially about smooth cylindrical portion 720 at 60 degrees from each other. Each of ridges 712 extends preferably between about 0.005″ and about 0.10″, above the smooth portion 710. Other configurations can be used, such as differently-shaped ridges or no ridges at all, in which the friction is provided between smooth cylindrical portion 720 and interior wall 508.
The frictional force required to remove writing instrument from cavity 506 depends on several factors, including the materials of which the ridges 712 and the interior wall 508 of cavity 506 are composed, the surface textures of the ridges and the interior wall of cavity 506, the contact area between the ridges and the inner surface of the cavity, and height of ridges 712 which defines the interference fit and determines the compression of the ridges. Additional ridges would increase the contact surface area, which would increase the friction. Skilled person can adjust the friction factors to produce a friction fit that is sufficient to secure the writing instrument 130 in windlass 122, but that permits removal of the writing instrument by a user having reduced dexterity due to stress and/or having hands wet and slippery with blood.
Ridges 712 preferably do not extend to the end of friction fit portion 704 from which the shaft 620 extends, but as described above provide for the gap 732 having a length 711 of preferably between about 0.01″ and about 0.10″, between the end of friction fit portion 704 from which shaft 620 extends and the beginning of ridges 712. The gap facilitates the insertion of the friction fit portion 704 into the cavity 506 of the windlass 106.
As the writing instrument is withdrawn, once the static friction is overcome, the friction decreases smoothly as the area of the ridges having contact with the cavity is reduced. The smooth reduction in friction makes it easier for a user having hands that are wet and slippery with blood to withdraw the writing instrument to write information on the retaining strap. Designing the friction fit portion 720 so that the friction reduces smooths eliminates the requirement for a large initial force, such as the force that would be required to overcome the resistance of a snap or detent.
With a snap or detent, there is a large initial force to overcome and then essentially no frictional force as the writing instrument is further withdrawn. In the embodiment of
Ridges 704, 804, 904, and 1004, referred to below ridges X04, preferably extend between about 0.01″ to 0.1″, preferably about 0.06″, above the major cylindrical surface of friction fit portion 710. When inserting the writing instrument into the interior cavity, the ridges are compressed slightly to maintain the writing instrument 130 within the interior cavity 506. The friction that keeps the writing instrument within the windlass cavity is determined by the materials of which the windlass and the ridges X04, as well as the number and geometry of the ridges. As the writing instrument is withdraw, the friction decreases in a relatively smooth manner as the contact area between the ridges and the interior wall of cavity 506 is reduced. The incremental reduction in friction makes it easier for a user having hands that are wet with blood to withdraw the writing instrument to write information on the retaining strap. Because the friction is spread amount the ridges, there is no initial large force needed to overcome.
In some implementations the writing instrument includes a ball point pen. The pen uses gel-type, waterproof, permanent ink or other marking substance. In some implementations, the windlass pen comprises a felt tip pen, a grease pencil, or a carbon pencil. The shaft is preferably made of copper or other material that will not rust or corrode. The writing substance may be stored within shaft 620.
The diameter of the standoff portion 622 is slightly larger than the inner diameter of the windlass cavity so that the stand-off portion will not go into the cavity 506, thereby preventing the writing instrument 130 from being inserted into the cavity 506 in windlass 106 up to the end 706. Keeping the end 706 positioned slightly way from the end of the windlass 106 facilitates grasping of the knurled end portion by a user.
The previous section describes an example of a tourniquet having a writing instrument configured to be stored in a windlass. In this section, the particular methods of such an implementation are described by reference to a series of flowcharts.
Method 1500 includes in step 1505 wrapping the tourniquet 100 around the subject appendage and then step 1510 includes looping the first end 120 of the belt 102 through the buckle 112. The tourniquet 100 is pulled reasonably tight in step 1515.
Step 1520 includes winding the windlass 106 to develop a tension force to tighten inner strap 104 which tightens the belt 102. After the windlass 106 has been sufficiently tightened to restrict the arterial blood flow in the limb, the windlass 106 is inserted into windlass clip 302 in step 1525 to prevent inner belt 104 from unwinding. In step 1530, the opening in the windlass clip is covered with the retaining strap 108, which includes hook-and-loop fasteners that mate with the hook-and-loop fasteners on the windlass clip to prevent the windlass from coming out of the windlass clip.
In step 1535, writing instrument 130 is removed from windlass 106 and in step 1540, the protective substance is removed from the tip of the writing instrument. The protective substance can be removed by merely starting to write with the writing instrument, with the protective substance coming off as the writing instrument contacts and moves relative to the markable surface. In step 1545, a user records the time at which the tourniquet was applied and any additional notes. The time can be recorded on the tourniquet itself, such as on the restraining strap 304. Alternatively, the time can be recorded elsewhere, such as on the clothing or skin of the patient. In step 1550, writing instrument 130 is then discarded or temporarily reinserted into windlass 106. If writing instrument 130 is temporarily reinserted in windlass cavity 506, it should eventually be disposed of because with the protective substance removed, the ink or other marking substance may eventually dry and render the writing instrument unusable.
Although the description described a tourniquet with an inner and outer strap, the writing instrument can be used with a windlass of any type of tourniquet.
A tourniquet having a windlass that stores a writing instrument is described. Although specific implementations are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific implementations shown. This application is intended to cover any adaptations or variations. For example, although described in medical terms, one of ordinary skill in the art will appreciate that implementations can be used in industrial environments or any other environment that provides the required function.
In particular, one of skill in the art will readily appreciate that the names of the methods and apparatus are not intended to limit implementations. Furthermore, additional methods and apparatus can be added to the components, functions can be rearranged among the components, and new components to correspond to future enhancements and physical devices used in implementations can be introduced without departing from the scope of implementations. One of skill in the art will readily recognize that implementations are applicable to future tourniquet devices, different pens, and new buckles.
The terminology used in this application is meant to include all tourniquets, buckles, belts and connecting members and alternate technologies which provide the same functionality as described herein
