Physics 101: How Do Cold Compresses Work Why Are They Effective in Reducing Inflammation

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Why a Cold Compress is Effective. The effectiveness of a cold compress has its basis in physics specifically the concepts of Thermodynamics, Fluid Mechanics and Entropy. Thermodynamic is the study of how temperature reacts within a defined system. Fluid Mechanic is the study of how fluids flow within a confine space. Entropy is a measure of a system’s naturally tendency to proceed towards spontaneous change.

These are simplified definitions but work perfectly well for our narrow discussion. However, of importance with all of the above topics is the need for a well defined system. Since the topic is “Why a Cold Compress is Effective”? Let’s take a system such as a swollen jaw. There are three essential areas that make up such a system, the source of the inflammation, some form of disruption in normal blood flow such as an incident due to impact damage. We also need a cold compact. Finally there is the thin wall between the two, the jaw itself.

The human body when it comes to the laws of physics is no different than the world we live in. The only difference is the size and how well we define the system under discussion. Having said that let’s combine all three. Using the above description where there is an injury to the jaw. The impairment causes the temperature transference from one area to another facilitated by the use of a liquid until equilibrium is reached. This localized internal trauma is a passive process similar to how a heat exchanger works but it also demonstrates how the body is subject to the laws of Thermodynamic, Fluid Mechanics and Entropy.

Take for example Entropy which is the measure of a system's tendency towards spontaneous change, in this case the focus would be on temperature stability or change as governed by the flow of a fluid, i.e. blood. However one of the laws of entropy is, in an islolated systems such as the body temperature tends not to decreases or increase unless energy such as the impact of a force or a cold compress is intorduced.

Then there is the aspect of Fluid Mechanics. It comes into play at the source of the impact damage. Since we are talking about the body the liquid of concern is blood. There are a number of forces acting on blood flow but the two which most effect our discussion are pressure delivered by a pump, the heart and friction forces as a result of any obstructions hindering the flow in any way. This is dependent on the conduit carry the liquid, the size of the artery and the condition of the walls.

The cold compress is the use of applied Thermodynamic. Effectively, temperature will continue to pass between the cold compress and the wall of the affected area until a new steady state or a point where temperature equilibrium exists. Systems are said to be in thermal equilibrium when the temperature does not change. By introducing the cold compress steady state is disrupted.

Essentially this is how a cold compress works. Temperature in combination with a liquid medium is somewhat like gravity the natural tendancy is to drop unless something else supports it. Meaning, it is easier to go from a higher state of potential energy to a lower state. Look at the blood in the affetcted area as stagnate. Thus at a lower temperature or at a lesser potential than the blood flowing in the rest of the body. Yet because of the mini system developed around the damaged area a state of equillibrium has been established an no new blood can get to the affected area.

The idea is to decrease swelling and improve blood flow. The cold compress effectively does this by lower the temperature of the affected area. Since temperature is subject to the laws of Entropy the tendancy is for it to naturally roll down hill. Temperature like most things in our reality, i.e. gravity, current and liquids, all tend to naturally travel from a higher potential to a lower potential with very little energy input. So the warmer blood will seek out the colder blood effectively setting up a heat pump situation by moving warmer fresh blood to the effected area. While at the same time slowing pushing the stagnate blood through. The result is an increase in blood flow. Which is what you need to help improve the healing process.