AY Honors/Home Nursing/Answer Key
Template:Merge 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, 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 crystallisation 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 below its crystallisation point, clicking makes it crystallise suddenly thereby releasing the energy of the crystal lattice. See sodium acetate for a more technical discussion.
The heat required for crystallisation is retained when the temperature drops and the solution becomes supersaturated. 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 boiling water for 15 minutes (however a few models dissolve in 10 minutes) which redissolves the sodium acetate in its own water of crystalisation. 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.
