Thermotherapy Lesson 1 23-24 PDF

THERMOTHERAPY PART 1 General Intervention Methods in Physical Therapy Degree in Physiotherapy Academic Year 23-24 USP-CEU SCHEME MODELS OF HEAT TRANSFER CONDUCTION CONVECTION RADIATION CONVERSION EFFECTS 2 MODES OF HEAT TRANSFER CONDUCTION CONVECTION RADIATION CONVERSION 3 CONDUCTION Heat transfer b...

THERMOTHERAPY PART 1 General Intervention Methods in Physical Therapy Degree in Physiotherapy Academic Year 23-24 USP-CEU SCHEME MODELS OF HEAT TRANSFER CONDUCTION CONVECTION RADIATION CONVERSION EFFECTS 2 MODES OF HEAT TRANSFER CONDUCTION CONVECTION RADIATION CONVERSION 3 CONDUCTION Heat transfer by direct contact between 2 materials. Heat is conducted from the warmer to the cooler material. 4 CONDUCTION Heat may be transferred to or from a patient by conduction. o Physical agent has a higher temperature than the patient’s skin: AGENT TO PATIENT. o Physical agents has a colder temperature than the patient’s skin: PATIENT TO AGENT 5 CONDUCTION Heat can be transferred by conduction from one area of the body to another. Heat transfer by conduction needs a direct contact between both materials. Insulation is needed. 6 CONDUCTION TRANSFER The greater the temperature difference between the agent and the body part, the faster the rate of heat transfer. The higher the temperature, the faster the temperature of the skin in contact with. Materials with high thermal conductivity transfer heat more faster (metals>water>air). The larger the area of contact, the greater the total heat transfer. 7 CONDUCTION TRANSFER Human body tissues present, in general, low thermal conductivity. Subcutaneous fat has low thermal conductivity acting as a insulator. Tissue’s thermal properties depends on its relative content in lipids, proteins and water. Great water content implies higher conductivity. 8 CONDUCTION TRANSFER The rate of temperature rise decreases in proportion to tissue thickness. When a thermal agent is in contact with the skin of a patient, the skin temperature increases the more, and deeper tissues are progressively less affected. The deeper the tissue, the less its temperature will change. 9 CONVECTION Heat transfer by circulation of a medium of a different temperature. Heat transfer in liquids (water, blood and air). During heating by convection thermal agent is in motion. 10 CONVECTION Heat transfer by convection transfers more heat in the same period of time than heat transfer by conduction when the same material at the same initial temperature is used. Differences between convective agents. 11 RADIATION Direct transfer of energy from a material with a higher temperature to one with a lower temperature without the need for an intervening medium or contact. Heat is transmitted across the emptiness through electromagnetic waves which are absorbed by the body. 12 CONVERSION Conversion from one type of energy to another. Conversion from a nonthermal energy into heat. Conversion does not require always direct contact between the thermal agent and the body. Heat depends on the power of the energy source (Watts). 13 MODES OF HEAT TRANSFER CONDUCTION CONVECTION RADIATION CONVERSION 14 THERMOTHERAPY CONCEPT The therapeutic application of heat is known as thermotherapy. Superficial therapy agents (up to 1 cm) HOT PACKS, PARAFFIN WAX-BATHS, INFRARED LAMPS Deep thermotherapy agents SHORTWAVE AND MICROWAVE DIATHERMY, ULTRASOUND 15 MODE OF HEAT TRANSFER CONDUCTION: Solid state: sand, dry wraps, heating blanket, hot packs. Semiliquid state: peloids, paraffin, parafango. CONVECTION: Hydrotherapy applications, steam baths and sauna. CONVERSION: Ultrasound, short and microwave diathermy. RADIATION: Infrared therapy. 16 Why we use thermotherapy? - To control pain - To increase soft tissue extensibility - To increase circulation - To accelerate healing 17 EFFECTS OF HEAT 1. HEMODYNAMICS EFFECTS: VASODILATION 2. NEUROMUSCULAR EFFECTS 3. METABOLIC EFFECTS 4. INCREASED COLLAGEN EXTENSIBILITY 18 1. HEMODYNAMICS EFFECTS: VASODILATION LOCAL OR DISTANT/REFLEX SUPERFICIAL HEATING AGENTS more vasodilation in local versus deeper vessels (muscles). To increase skeletal muscle flow: DEEP HEATING AGENTS. 19 1. HEMODYNAMICS EFFECTS: VASODILATION 20 DISTANT OR REFLEX VD Distant areas from site of heat application. Increase blood flow when is difficult to apply heat directly 21 VASODILATION Heat produces HYPEREMIA: Improves oxygenation and cellular nutrition Pathological Products Absorption Increase Germicidal and anti-inflammatory effect. Analgesic and Antispasmodic Effect Tissue Renovation 22 2. NEUROMUSCULAR EFFECTS 2.1. CHANGES IN NERVE CONDUCTION VELOCITY AND FIRING RATE 2.2. INCREASED PAIN THRESHOLD 2.3. CHANGES IN MUSCLE STRENGTH 23 2.1. CHANGES IN NERVE CONDUCTION VELOCITY AND FIRING RATE Increasing tissue temperatures has been shown: to increase nerve conduction velocity. to reduce the firing rate of motor neurons (reduce the muscle spasm) 24 2.1. CHANGES IN NERVE CONDUCTION VELOCITY AND FIRING RATE External, very hot and short-time stimulus increases muscle tone and nervous sensitivity. External, very hot and long-time stimulus produces muscle relaxation and they have an analgesic and sedative effect. 25 2.2. INCREASED PAIN THRESHOLD A direct and immediate decrease of pain by the GATE CONTROL THEORY 26 2.2. INCREASED PAIN THRESHOLD A later and long-lasting reduction of pain by reduction of the ischemia and muscle spasm or facilitation of tissue healing. Thermoreceptors cause VD increasing blood flow and reducing pain. Ischemia decreased due to the reduction of spasms in muscles. VD accelerates tissue healing. 27 2.3. CHANGES IN MUSCLE STRENGTH Muscle strength and endurance decrease during the initial 30 minutes after heat application. After this and over the next 2 hours muscle strength gradually recovers and returns to pretreatment levels. 28 3. METABOLIC EFFECTS Heat increases the rate of all chemical reactions, including enzymatic reactions (39-43ºC). Any increase in enzymatic activity will result in an increase in the rate of cellular biochemical reactions, thus increasing oxygen uptake and tissue healing. 29 4. INCREASED COLLAGEN EXTENSIBILITY Soft tissue heated prior to stretching maintains a greater increase in length after the stretching force is applied (PLASTIC DEFORMATION). 40-45ºC FOR 5-10 MINUTES. Soft tissue not heated prior to stretching increases in length while the force is appied but loses most of the increase when the force is removed (ELASTIC DEFORMATION) 30 TAKE-HOME MESSAGE!!!! 4 modes of heat transfer in thermotherapy: conduction, convection, conversion, radiation Different agents to produce superficial-deep heat. Insulation important to reduce the amount of heat. Convection transfers more heat in the same period than conduction. Conversion heating depends on the power of the energy source. 31 BIBLIOGRAPHY Cameron MH. Physical Agents in Rehabilitation: From Research to Practice. Elsevier, 2021 Bélanger AY. Evidence-Based Guide to Therapetic Physical Agents. Elsevier Churchill Livingstone 2.002. Watson T. Electrotherapy: Evidence-Based Practice. Elsevier, Churchill Livinstone, 2008. Bélanger AY. Therapeutic Electrophysical Agents. Evidence Behind Practice. Lippincott Willians & Wilkins, 2014. 32