Minor ailments and aches and pains are often treated with superficial heat although this modality is much less commonly used by physiotherapists than it used to be. The heating effect is shallow as the fat layer under the skin acts as an insulator against the heat, preventing transfer of energy to deeper tissues. The heat causes an increase in blood flow to the skin which moves heat away from the area treated and reduces the effect further. Techniques of heating are varied and fall into three main groups: heat convection, heat conversion and heat conduction.
In conductive heating the heat transfer is accomplished from one object to the other by static transfer without motion of the medium and the tissues involved and the heat medium closely in contact. Examples of this type of heat application are wax or paraffin baths, hot compresses, hot water baths, electric heat pads and hot packs. Less often used is convective heating where the heating medium is in motion while it transfers heat, examples being hot air devices and whirlpool baths. If light energy from a radiant source is changed into heat in the superficial skin then the process is conversion heating.
Various parameters of the heat application determine how the bodily tissues react to the temperature changes. This depends on the size of the region under treatment, how quickly the temperature rises, how long the heat is applied for and the level of temperature achieved in the tissues. Hot packs, sometimes called hydrocollator packs, uses the conductive heating effect and can be effective but there is a risk of burns as the tissues can be overheated. Hot packs do not mould very effectively to uneven body parts such as the foot or ankle, making predictable heating unlikely. Reduction in the local blood supply can occur with pressure of the pack on the leg or vice versa, giving increased heating.
after, for example, persistent ankle swelling after fracture or repeated ankle sprains. Hot and cold water baths are used with a differential of 25 degrees centigrade between them. The cycle bringing on the greatest changes in blood supply involves ten minutes in the hot bath followed by one in the cold bath, continuing with four minutes hot and one minute cold. This cycle can be repeated until thirty minutes have elapsed and be performed several times a day. This technique uses convective heating which is also employed in pool or hydrotherapy.
Hydrotherapy involves immersion of the body in a large pool of warm water and the heat and support from the water helps pain and weakness and allows increased joint ranges particularly in arthritic conditions. A temperature above 34 degrees centigrade is used and this heat can have side effects such as changes in blood pressure as the heat and water pressure affects the body.
A technique of conversion heating is to use radiant energy of which the commonest form is infra-red radiation, whereby high energy light particles enter the skin and are converted into heat. Heat lamps, which can be purchased on the high street, are an example, and have some visible spectrum of red light also to indicate they are on. These can be used for minor aches and pains with muscle spasms and for osteoarthritic joints or backache.
There is no deep heat effect and skin sensory nerves are sedated, reducing discomfort by local and central means as heat inputs are received in the spinal cord. Heat treatment needs to be carefully set up by a physiotherapist as burns are possible. The inverse square law is important, as you get four times the dose of radiation by merely cutting the skin to source distance in half.
Heat therapy should not be routinely applied and physiotherapists make careful clinical judgements as to whether superficial heating is indicated in the light of the effects being small, short lived and not deep. Skin sensibility should be normal for this method as a deficiency in this could risk a burn as the patient cannot tell when their skin is being overheated. Heating should be avoided in areas of infection and its use in inflammation should be clinically reasoned for appropriateness. - 14130
In conductive heating the heat transfer is accomplished from one object to the other by static transfer without motion of the medium and the tissues involved and the heat medium closely in contact. Examples of this type of heat application are wax or paraffin baths, hot compresses, hot water baths, electric heat pads and hot packs. Less often used is convective heating where the heating medium is in motion while it transfers heat, examples being hot air devices and whirlpool baths. If light energy from a radiant source is changed into heat in the superficial skin then the process is conversion heating.
Various parameters of the heat application determine how the bodily tissues react to the temperature changes. This depends on the size of the region under treatment, how quickly the temperature rises, how long the heat is applied for and the level of temperature achieved in the tissues. Hot packs, sometimes called hydrocollator packs, uses the conductive heating effect and can be effective but there is a risk of burns as the tissues can be overheated. Hot packs do not mould very effectively to uneven body parts such as the foot or ankle, making predictable heating unlikely. Reduction in the local blood supply can occur with pressure of the pack on the leg or vice versa, giving increased heating.
after, for example, persistent ankle swelling after fracture or repeated ankle sprains. Hot and cold water baths are used with a differential of 25 degrees centigrade between them. The cycle bringing on the greatest changes in blood supply involves ten minutes in the hot bath followed by one in the cold bath, continuing with four minutes hot and one minute cold. This cycle can be repeated until thirty minutes have elapsed and be performed several times a day. This technique uses convective heating which is also employed in pool or hydrotherapy.
Hydrotherapy involves immersion of the body in a large pool of warm water and the heat and support from the water helps pain and weakness and allows increased joint ranges particularly in arthritic conditions. A temperature above 34 degrees centigrade is used and this heat can have side effects such as changes in blood pressure as the heat and water pressure affects the body.
A technique of conversion heating is to use radiant energy of which the commonest form is infra-red radiation, whereby high energy light particles enter the skin and are converted into heat. Heat lamps, which can be purchased on the high street, are an example, and have some visible spectrum of red light also to indicate they are on. These can be used for minor aches and pains with muscle spasms and for osteoarthritic joints or backache.
There is no deep heat effect and skin sensory nerves are sedated, reducing discomfort by local and central means as heat inputs are received in the spinal cord. Heat treatment needs to be carefully set up by a physiotherapist as burns are possible. The inverse square law is important, as you get four times the dose of radiation by merely cutting the skin to source distance in half.
Heat therapy should not be routinely applied and physiotherapists make careful clinical judgements as to whether superficial heating is indicated in the light of the effects being small, short lived and not deep. Skin sensibility should be normal for this method as a deficiency in this could risk a burn as the patient cannot tell when their skin is being overheated. Heating should be avoided in areas of infection and its use in inflammation should be clinically reasoned for appropriateness. - 14130
About the Author:
Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapy, back pain, orthopaedic conditions, neck pain, injury management and physiotherapists in Rugby. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.
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