Patent Application
20160228289
1. Field of Invention
The present invention relates generally to cold therapy, and specifically to improving the safety and effectiveness of a cold therapy unit which reduces pain and swelling at an injury site of a patient.
2. Description of Related Art
Cold therapy or cryotherapy (e.g., ice) is used to reduce pain and swelling, otherwise known as edema formation, from an acute injury or post-surgery site. The therapy is especially useful for injuries such as sprains, strains, pulled muscles, and pulled ligaments during sports and other activities. Cold therapy is also often recommended by orthopedic surgeons following surgery, as ice is one of the principles of Rest, Ice, Compression, and Elevation (RICE) therapy.
The ice principle, known as cryotherapy, is the use of cold or ice to lower the temperature of the injured tissue, which reduces the tissue's metabolic rate and helps the tissue survive the period following the injury. In a therapeutic setting, cryotherapy has become one of the most common treatments in orthopedic medicine.
Alternatives to ice include cold wraps such as re-freezable gel packs, which are less messy and reusable. Another popular alternative is portable cold therapy units, which are an effective and convenient alternative to icing, as the cold therapy unit circulates ice water through a treatment pad wrapped around an injury or surgery site of the patient to reduce pain and swelling. Cold therapy unit are often prescribed by doctors or selected by patients after surgery for use in their home.
According to the medical community's guidelines, the length of time that cold can be applied to an injury or wound site depends on the temperature of the treatment medium. For example, ice, which will have a surface temperature of 32 degrees F., should generally be limited to a maximum of 15-20 minutes at a time and no more frequently then every two hours. Exceeding these established limitations puts the patient at risk for further injury. For example, exceeding the 20 minute treatment limitation can cause frostbite or other damage to skin, tissue, and nerves. However a cold therapy unit, with a treatment pad having a surface temperature greater than 45 degrees F., can be applied continuously for as long as needed to reduce pain and swelling.
The portable cold therapy units existing in the prior art consist of a reservoir which hold ice and water, a pump to circulate the water and a treatment pad through which the water is circulated. All of the units that are intended for continuous use, (greater than 20 minutes), rely on body heat from the patient to warm the water from just above freezing to a safe level. This is typically done by controlling how fast the water flows through the pad, typically about 4 oz. per minute. Unfortunately there are many variables other than flow rate that effect the resulting temperature of the treatment water such as the size of the treatment pad, the amount of blood circulation the patient has at the treatment site and the location of the treatment site on the patient. For example an ankle typically has poor circulation while a shoulder has very good circulation. Also an ankle treatment pad is typically much smaller than a shoulder pad therefor the water would remain in the ankle pad for a very short time not allowing much time to warm up while it would remain in the shoulder pad much longer therefor warming to a much greater extent. The result is that the ankle is exposed to temperatures lower than what are safe and the shoulder doesn't see low enough temperatures to help much in the treatment.
The manufacturers of prior art devices deal with this issue in a couple of ways. One way is to put a thermometer in the line returning from the treatment pad to the reservoir and provide controls for the patient or medical practitioner to control the flow rate of the treatment fluid so that the desired temperature can be maintained. This method has some major drawbacks. One drawback is that the heath care practitioner as well as the patient need to fully understand the proper use of the device as well as the risks if not used according to directions. Unfortunately, the patient often does not read through the instructions and warnings and sometimes concludes that if a little is good a lot is better which often results in serious skin or nerve damage. Since the treatment area is numb from the cold the patient does not feel any pain from the damage that is occurring.
Another drawback to manually controlling temperature is that it sometimes results in ineffective treatment. This is because one of the major influences on the amount of heat that is transferred from the body to the treatment pad is the thickness and number of layers of dressing between the treatment pad and the skin. What happens is that a lot of dressing equals a lot of insulation resulting in little heat transfer which results in the thermometer showing that the water is too cold. The patient, according to the instructions, would decrease the flow resulting in a warmer treatment pad and thermometer reading. With that much insulation, in order to get enough heat transfer for the treatment to be affective, the patient would actually need to increase the flow rate rather than decrease resulting in a cooler treatment pad.
Another way that manufacturers of prior art cold therapy units deal with the problem of different treatment sites and different sizes treatment pads having different heat transfer rates, is by having a different fixed flow rate for each type of treatment pad. For example, an ankle pad might have a flow rate one quarter of that of a shoulder pad. While this method is safer than the manual control method, since the patient or medical practitioner cannot adjust the flow rate, it still does not address the issue of patients having differing blood circulation at any given treatment site due to factors such as age, health, smoking, prior surgeries at that location, etc.
There is another major problem with all of prior art portable units that rely on the water warming from just above freezing to a safe level in a single pass through the pad. The water enters the inlet port of the pad at just above freezing, travels an arduous path around barriers that prevent the water from shortcutting from the inlet directly to the outlet and then the water exits the outlet port at approximately 50 degrees F. What this means is that the inlet quadrant of the pad will be close to freezing while the outlet quadrant will be about 15 degrees warmer. This could result in skin or nerve damage localized at the inlet quadrant of the pad.
Many of the injuries such as skin necrosis, blistering and nerve damage, observed in patients using cold therapy units, are also observed in patients who did not use cold therapy. This and the fact that there is no way to determine what temperature the treatment site experienced, makes it very difficult if not impossible to determine the exact cause of the injury. This confusion has led to each manufacturer spending millions of dollars each year between litigation and injury compensation for cases that may or may not been a result of their product.
It is therefore advantageous to have a portable cold therapy unit that delivers a treatment fluid to a treatment pad entering the pad at consistent and safe temperature. It is also desirable that the treatment fluid circulates at a relatively high flow rate so that the temperature of the fluid exiting the pad is only slightly warmer than the fluid entering the pad. Such a unit would not be subject to miss-adjustment, cold spots on the pad, and in the event of litigation, testing of the unit to determine if it was maintaining a safe temperature is more easily accomplished.
Embodiments of the present invention provide a cold therapy unit incorporating a cold reservoir containing a cold treatment fluid, typically water with ice and a treatment pad with an inlet line and an outlet line. A thermo-mechanical mixing valve receives treatment fluid from the reservoir and warmer fluid from the pad in a ratio that results in treatment fluid of the desired temperature. A pump delivers that treatment fluid to the inlet line on the pad. A portion of the treatment fluid exiting the pad through an outlet line will return to the reservoir and a portion to the mixing valve as required to maintain a predetermined temperature in the mixing valve.
In one embodiment of the present invention the mixing valve employs a sealed chamber with two inlet ports on opposite sides of the chamber, the first inlet port receiving cold fluid from the reservoir and the second inlet port receiving warmer fluid from the outlet line of the treatment pad. A bimetal strip reactive by bending in accordance with exposure temperature is oriented in the chamber to block off a first one of the two inlet ports when the temperature of the fluid in the chamber is below a predetermined lower threshold or the second one of the two inlet ports when the treatment fluid in the chamber is above a predetermined upper threshold. Adjustment screws calibrate the temperature at which the fluid in the chamber is maintained.
In another embodiment of the present invention the bimetal mixing valve employs a sealed chamber with two inlet ports on opposite sides of the chamber, the first inlet port receiving cold fluid from the reservoir and the second inlet port receiving warmer fluid from the outlet line of the treatment pad. A dual ended tapered needle valve is adapted for one end to be received in each of the inlet ports to gradually increase or decrease the flow of fluid as the needle valve is retracted from or inserted into each of the ports. A bimetal strip which is reactive in accordance with exposure temperature is oriented in the chamber to act on the dual ended needle valve causing the respective ends to be inserted or retracted from each of the ports depending on the temperature of the fluid in the chamber causing a restriction of flow in the first inlet port when the fluid in the chamber is below a predetermined threshold temperature or in the second inlet port when the treatment fluid in the chamber is above a predetermined threshold temperature. Adjustment screws are provided to calibrate the temperature at which the fluid in the chamber is maintained.
In another embodiment of the present invention the mixing valve employs a sealed chamber with two inlet ports on opposite sides of the chamber. A first inlet port receives cold fluid from the reservoir and a second inlet port receives warmer fluid from the outlet line of the treatment pad. A bimetal coil which is reactive by winding or unwinding in accordance with exposure temperature is oriented in the chamber to block off the first inlet port when the fluid in the chamber is below a predetermined threshold temperature or the second inlet port when the treatment fluid in the chamber is above a predetermined threshold temperature. An adjustment screw at the center of the bimetal coil is employed to calibrate the temperature at which the fluid in the chamber is maintained.
In another embodiment of the present invention the bimetal mixing valve employs a sealed chamber with two inlet ports on opposite sides of the chamber, a first inlet port receiving cold fluid from the reservoir and a second inlet port receiving warmer fluid from the outlet line of the treatment pad. A dual ended tapered needle valve is adapted for one end to be received in each of the inlet ports to gradually increase or decrease the flow of fluid as the needle valve is retracted from or inserted into each of the ports. A bimetal coil which is reactive by winding or unwinding in accordance with exposure temperature is oriented in the chamber to act on the dual ended needle valve causing the respective ends to be inserted or retracted from each of the ports depending on the temperature of the fluid in the chamber causing a restriction of flow in the first inlet port when the fluid in the chamber is below a predetermined threshold temperature or in the second inlet port when the treatment fluid in the chamber is above a predetermined threshold temperature. An adjustment screw at the center of the bimetal coil is employed to calibrate the temperature at which the fluid in the chamber is maintained.
The features, functions, and advantages that have been discussed can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings.
Embodiments disclosed herein provide a novel method and apparatus for maintaining a safe temperature in ice water cooled cold therapy pads using a thermo-mechanical valve for flow mixing of pumped water to the pad by receiving return flow from the pad and a cold reservoir with ice water supply. In one embodiment the return flow from the pad is routed through a holding reservoir before being routed to the thermo-mechanical valve.
Referring to the drawings,
In the first embodiment, the connection between the first input port and outlet line 16 is direct through first bifurcated line 28a and a second bifurcated line 28b is provided to recirculate water to the reservoir 24 for specific flow conditions to be described subsequently. In a second embodiment shown in
Initially when the pad 12 is first applied to a patient and the pump 10 is turned on, the water pumped through the thermo-mechanical mixing valve 18 will be drawn from the cold reservoir 32 and into the pad which will cool to a little above freezing (or the refrigerated temperature of the water in the cold reservoir). Because the water is below a lower temperature threshold, the thermo-mechanical mixing valve will substantially close off the second inlet port 22 receiving the iced water and only recirculate the water from the pad outlet line 16, directly from the pad outlet line for the first embodiment or from the holding reservoir 30 for the second embodiment, through inlet port 20 and through the pump 10 to the pad 12 until the water reaches the predetermined safe temperature. At that point the thermo-mechanical mixing valve 18 will adjust to allow inflow through cold conduit 26 to the second inlet port 22 and allow some iced water to enter the system to maintain that preset temperature. With a large pad such as a shoulder pad, the unit may have a hard time keeping up with the amount of heat the body is adding to the system and the thermo-mechanical mixing valve may shift to close the first inlet port 20 upon reaching a high threshold temperature resulting in a higher percentage of iced water flowing through the pad 12. In any case, no matter what size pad, where it is placed on the body, or the health of the patient's circulation, the water being fed to the pad 12 will always be adjusted automatically to remain in a safe range.
The thermo-mechanical mixing valve 18 operates automatically for water temperature adjustment. Water flowing through the valve is in contact with an adjustment element which is reactive to the temperature to which it is exposed and thus alters shape based on the temperature of the water. In a first example a bimetal valve 18a may be employed as the thermo-mechanical valve by the embodiments disclosed herein.
Greater control of the flow rates of water entering the sealed chamber of the bimetal valve can be accomplished as shown in
Alternatively, as shown in
As with the bimetal strip, greater control of flow can be achieved with the bimetal coil 52 as shown in
In yet another alternative embodiment, as shown in
As with the bimetal mixing valves, greater control of flow can be achieved with the pressure valve as shown in
The embodiments disclosed herein allow a method for operation of a cold therapy pad as shown in
Having now described various embodiments of the disclosure in detail as required by the patent statutes, those skilled in the art will recognize modifications and substitutions to the specific embodiments disclosed herein. Such modifications are within the scope and intent of the present disclosure as defined in the following claims.
