Hydro collator packs

Heat exchange by conduction When an object is heated by a source in contact with it, the speed at which the heat will flow and cause a rise in temperature will depend upon the thermal conductivity of the source and the substance. The thermal conductivity of water is greater than that of fat. Tisseues with high water content will conduct faster than tissues with low water content.

The specific heat of the tissue will also govern the amount of heat needed to raise temperature by any particualr amount. Fat has a specific heat of only 0.6 and can therefore be heated with less expenditure of energy than for water (specific heat = 1.0)

Hydro collator packs The use of moist heat as a therapeutic agent is one of the oldest forms of medicine. Today we have efficient automatic units producing a uniform and constant temperature to heat steam packs. The heating unit is called a hydro collator unit.

The hydro collator unit is a stainless steel tank with silica gel packs are heated The capacities of the machines vary, and all units have insulated bases, the larger machines being insulated with fiberglass. The units contain a wire rack which act as a devider for the packs and prevents contact of packs with the bottom of the tank. The heatere is thermostatically controlled and maintains water in the unit at a temperature between 76°c and 80°c

A hydro collator packs is a fabric envelop containing silica gel. The main property of the gel is its capability to absorb many times its own volume of water and, when heated, to give off moist heat for 30 to 40 minutes. The packs are heated in a hydro collator unit. Packs come in varying sizes and shapes. They are designed to fit neraly any body contour and are uesd repeatedly.

The part selected to be treated must be able to tolerate pressure of the pack (approximately 500 to 800 gram) and to tolerate a 7 to 10 degree rise in temperature. It is important to ensure that the circulation can dissipate heat, and that skin sensation responses to thermal differences are normal, as it is easy to produce a burn.

Biological effect of hydro collator packs 1- heat production The effect of the packs on the tissues is due to mainly the heat generated, and is subject to the quantity and depth of penetration of the long infrared rays emitted from the pack. When infrared is absorbed by tissues it produces heat. The penetration of the rays is no more than 0.5 to 1 mm deep. The conduction depth is governed by the properties of the underlying fat, muscle, connective tissue and bone.

Temperature elevation will depend upon the patency of the circulation and sensation, and the ability of the tissues to dissipate heat. Bone and fat will impede heat distribution— fatty tissue having a low specific heat will heat rapidly and will cause heat conduction away from the site. Temperature rise takes place if the heat generated exceeds the rate at which the tissue can dissipate the heat

2- skin temperature Within 7 minutes there is a maximum 7 to 8 degree rise in temperature and then drop of about 2 degree over the remainder of the 20 to 30 minutes of application period

3- subcutaneous tissue and muscle There is a mximum rise about 1-3°c after maximally 30 minute and drop within one hour

4- hyperaemia There is increased vasodilatation of the main venous channels in the skin through the opening of the arteriovenous anastomosis, by –passing the capillaries, since the main function of the skin circulation is heat regulation. Skin blood flow increases than twofold and remains at a constant level for about 15 minutes. This is due to the release of histamine like substance and brady kinin producing vasodilatation of the capillaries.

5- sedative effect Moist heat is a safe analegesic and a muscle relaxant.

Indication 1- pain and muscle spasm 2- inflammation 3- oedema 4- adhesion

Contra-indication 1- impaired skin sensation 2- circulatory dysfunction 3-Analgesic drugs 4- infections and open wounds 5- cancer and tuberculosis 6- gross oedema 7-lack of comprehension 8- deep x rays