Physiological Properties of Thermal Modalities (2)

Physiological Effects of Heat 1. Haemodynamic Effects: Vasodilation Increases the rate of blood flow (locally and systemically) It is increases more locally

1. Haemodynamic Effects: It occurs due to: Direct activation  on the smooth muscles of blood vessels Indirect activation Effect on spinal cord on the grey matter  smooth muscle Sympathetic nervous system  vasodilation

1. Haemodynamic Effects: No increase in the temperature of most muscles Protect body from excessive damage Convection reduce the risk of burning

2. Neuromuscular Effects: Change in nerve conduction velocity and firing rate: Change in nerve conduction velocity (N.V.C) Decrease conduction latency (in sensory & motor nerves) Increase pain threshold Direct  gating Indirect   ischemia +  muscle spasm

3. Metabolic Effects: Increase metabolic rate Increase the rate of chemical reactions including enzymatic activity Up to 45°C Increase rate of cellular biochemical reactions Increase O2 uptake Increase healing

4. Alter Tissue Extensibility : Increase collagen extensibility Stretching the soft tissue without heating  elastic deformation Stretching the soft tissue with heating  plastic deformation Plastic deformation is due to the change in the viscoelasticity of collagen fibers + the organization of collagen fibers 40 - 45°C from 5 – 10 minutes (when applying the agent apply for 15 minutes)

Physiological Effects of Heat Factors affecting these physiological effects: Size of the heated area Depth of absorption of specific radiation Duration of heating Frequency of treatment Intensity of radiation Method of application

Therapeutic Effects of Heat Pain control: Direct due to gating Indirect through healing,  muscle spasm,  ischemia  Skin temperature Not recommended for acute inflammation. Remember! Applying hot agents to acute inflammation might cause destruction of the tissue

Therapeutic Effects of Heat Increase range of motion and decrease joint stiffness  Soft tissue extensibility Passive stretch (45°C for 5-10 minutes)  Extensibility and viscoelasticity of particular structures (joint capsule, ligaments ..etc) Superficial stretching (hot pack, infrared, paraffin) Deep stretching (ultrasound, shortwave diathermy)

Therapeutic Effects of Heat Accelerate healing  Circulation  Enzymatic activity O2, nutrients, remove waste products In chronic inflammation (third & forth stages of inflammation) Inflammation & healing rapidly

Therapeutic Effects of Heat Reduction of muscle spasm Golgi tendon Muscle spindle

Prophylaxis of pressure sores Sedative effect Sleeping Prophylaxis of pressure sores  Blood flow Risk of skin breakdown Skin disease Like I.R. Precursor for other treatment (Before stretching, exercises ,massage)

Contraindications of Superficial Heating Acute injury or inflammation Recent or potential hemorrhage Thrombophlibitis Impaired sensation Impaired mentatiion Malignancy I.R irradiation to eyes damage of retina (use a goggle)

Precautions Pregnancy Impaired circulation Poor thermal regulation Edema chronic  hot agent + elevation Cardiac insufficiency Metal in the area Over an open wound Over area where topical counterirritant hae recently been applied

Adverse Effects of Thermo-therapy Burns  Intensity Too long time of application Patient fall asleep Contraindicating Fainting Vasodilation   blood flow in the area treated   blood pressure

Adverse Effects of Thermo-therapy Bleeding Skin and eye damage from I.R irradiation

Conductive Agents Heat Methods of Application Two types of heat: Dry heat: increase surface temperature Wet heat: increase temperature slightly deeper Conduct techniques: Superficial Deep

Conductive Agents Heat Methods of Application Superficial contact heat depends on: Intensity of heat Length of exposure to heat Thermal medium for surface heat

Conductive Agents Heat Methods of Application Heating tempreture 40 – 45°C Above this level  burning Below this level  mild effect Maximum elevation of skin temperature within 6-8 minutes Deep contact  deep heat modalities

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