AY Honors/Home Nursing/Answer Key
A heating pad is a pad used for warming of parts of the body in order to manage pain. Localized application of heat causes the blood vessels in that area to dilate (Vasodilation), enhancing perfusion to the targeted tissue. Such pads are now usually electrical or chemical, though in the past "hot water bottles" were used and sometimes still are.
Electric pads usually operate from household current and must have protections against overheating. Chemical pads employ a chemical heat reservoir (see below) or a one-time chemical reaction such as catalyzed rusting of iron.
Types
A sodium acetate heat pad contains a supersaturated solution of sodium acetate (CH3COONa) that heats when you start the crystallization process by clicking the piece of metal that is in the liquid. Because the liquid is supersaturated, i.e. the temperature of the solution is raised so that more Sodium Acetate is in solution than could be normally dissolved at room temperature. Clicking makes it crystallize suddenly thereby releasing the energy of the crystal lattice. See sodium acetate for a more technical discussion.
The heat is released on solidification, which is triggered by flexing a (patented[1]) small flat disc of notched ferrous metal which releases very tiny adhered crystals of sodium acetate [2] into the solution which then act as nucleation sites for the recrystallization of the remainder of the salt solution.
To reuse the pad, it is placed in boiling water for 10-15 minutes which redissolves the sodium acetate in the contained water, once again creating a supersaturated solution. Once the pad has returned to room temperature it can be triggered again.
A microwavable heating pad is a heating pad that is warmed by placing it in a microwave oven before use. Microwavable heating pads are typically made out of a thick insulative fabric such as flannel and filled with grains such as buckwheat or flax seed. Due to their relative simplicity to make, they are frequently sewn by hand, often with a custom shape to fit the intended area of use.
Often, aromatic compounds will also be added to the filler mixture to create a pleasant or soothing smell when heated. The source of these can vary significantly, ranging from adding essential oils to ground up spices such as cloves and nutmeg, or even dried rose petals.
A moist heating pad is a heating pad that is used to dry the users skin. These pads register temperatures from 170 to 180 degrees Fahrenheit (76 to 82 °C) and are intended for deep tissue treatment and should never be left turned on unattended. Mainly used by physical therapists but can be found for home use.
Function
Many episodes of pain come from muscle exertion or strain, which creates tension in the muscles and soft tissues. This tension can constrict circulation, sending pain signals to the brain. Heat application eases pain by:
- dilating the blood vessels surrounding the painful area. Increased blood flow provides additional oxygen and nutrients to help heal the damaged muscle tissue.
- stimulating sensation in the skin and therefore decreasing the pain signals being transmitted to the brain
- increasing the flexibility (and decreasing painful stiffness) of soft tissues surrounding the injured area, including muscles and connective tissue.
As many heating pads are portable, heat may be applied as needed at home, at work, or while traveling. Some physicians recommend alternating heat and ice for pain relief. As with any pain treatment, a physician should be consulted prior to beginning treatment.
