Download Physiological Properties of Thermal Modalities Lecture Notes 2

Physiological Properties of
Thermal Modalities (2)
Physiological Effects of Heat
1. Haemodynamic Effects:
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Vasodilation
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Increases the rate of blood flow (locally and
systemically)
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It is increases more locally
1. Haemodynamic Effects:
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It occurs due to:
A.
Direct activation  on the smooth muscles
of blood vessels
B.
Indirect activation

Effect on spinal cord on the grey matter 
smooth muscle
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Sympathetic nervous system  vasodilation
1. Haemodynamic Effects:

No increase in the temperature of most
muscles
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Protect body from excessive damage
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Convection reduce the risk of burning
2. Neuromuscular Effects:
A.
Change in nerve conduction velocity and
firing rate:
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B.
Change in nerve conduction velocity (N.V.C)
Decrease conduction latency (in sensory &
motor nerves)
Increase pain threshold
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Direct  gating
Indirect   ischemia +  muscle spasm
3. Metabolic Effects:
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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 :
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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:
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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
A. Pain control:

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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
B. Increase range of motion and decrease
joint stiffness
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 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
C. Accelerate healing
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 Circulation
 Enzymatic activity
O2, nutrients, remove waste products
In chronic inflammation (third & forth stages of
inflammation)
 Inflammation & healing rapidly
Therapeutic Effects of Heat
D. Reduction of muscle spasm
 Golgi tendon
 Muscle spindle
 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
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Recent or potential hemorrhage

Thrombophlibitis
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Impaired sensation
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Impaired mentatiion
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Malignancy
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I.R irradiation to eyes damage of retina (use a goggle)
Precautions
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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
A. Burns
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 Intensity
Too long time of application
Patient fall asleep
Contraindicating
B. Fainting
 Vasodilation   blood flow in the area treated
  blood pressure
Adverse Effects of Thermo-therapy
A. Bleeding
B. 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
 Good Luck 