Thermal: heat and cold Flashcards Preview

PHTY2240 > Thermal: heat and cold > Flashcards

Flashcards in Thermal: heat and cold Deck (16):
1

Sensory appreciation of temperature

0 - 13 = very cold
13 - 18 = cold
18 - 27 = cool
27 - 33 = neutral
33 - 37 = warm
37 - 40 = hot
40 - 44 = very hot
> 45 = painful

2

Heat capacity and conductivity

• Different materials have different heat capacity and conductivity

3

Heat transfer:
3 modes

• Conduction
• Convection
• Radiation

4

• Conduction

• The kinetic motion of atoms and molecules being passed from one to the next

5

• Convection

• By the movement of molecules (liquid or gas) from one place to another e.g. convection ovens
wind

6

• Radiation

• Conversion of heat energy to electromagnetic radiation

7

** Physiological effects of heat:

• Increased metabolic activity
• Decreased viscosity
• Blood vessel changes
• Collagen tissue changes
• Pain relief and reduction in muscle spasm
• Tissue healing and resolution of inflammation
• Cutaneous thermoreceptors signal temperature change

8

Increased metabolic activity

•Metabolic activity inc. with rise in temperature
• Van’t Hoffs Law ‐ 13% increase in metabolism for each 1 degree (eg. 4° rise
– 50% increase in metabolism)
• Increases O2 uptake and healing process
• However, also increase activity of destructive process (enzymes)
• > 45° starts to decrease
• > 50° proteins (enzymes) denature
• For therapy, temperature changes in deep tissues should be no greater than 5‐6 oC above or below core temperature.

9

Viscosity

• Decrease viscosity of fluid
• Therefore less resistance to flow and more blood into the area
• Affects blood, lymph and fluid movement within tissues, joints
• Clinical significance not clear but may help to flush out inflammatory products

10

Blood vessel changes

• LOCAL changes thought to be due to several mechanisms:
• Direct effects on local capillaries, arterioles, venules‐ dilate
• vasodilation of local blood vessels is an axon reflex triggered by stimulation of polymodal receptors in the skin
• Increased metabolism leading to more carbon dioxide and lactic acid – greater acidity – provokes dilation of blood vessels
• a mild inflammatory reaction
• GENERAL
• 20 mins ‐ general warming of body • drop in blood pressure

11

Collagen tissue changes

• Collagen becomes more extensible
• At 40‐45°C – collagen shown to be more extensible
• Only occurs if the tissue is simultaneously stretched
(Robertson et al 2006)
Therefore, heat and stretching should result
• greater increase in length
• less force required
• reduced risk of tissue tearing

12

Nerve stimulation

• Nerve activity is markedly affected by changes in temperature
• Heat stimulates sensory receptors
• Stimulation of afferent nerves may act on pain gate control mechanism ‐ block pain – local analgesia
• Heat affects muscle spindle nerve endings and Golgi tendon organs and may result in reduced muscle spasm

13

Increase blood and tissue fluid

• Increased metabolism
• Vasodilation
• Lowered blood viscosity

All Increase in fluid exchange across capillary walls and cell membranes
• Speeding up healing processes

14

Therapeutic effects

Therapeutic effects
• Tissue healing
• In the sub acute to chronic phases of the inflammatory cycle
• Not well supported by recent literature but general agreement
• Relief of pain
• Most common reason for use
• Some evidence (Barbour et al 1986, Sluka et al 1999, On et al 1997)
• Reduction o fmuscle spasm
• Sedative effect
• Increase joint ROM
• Prophylaxis (prevention)of pressure sores
• Reduction of chronic oedema
•Precursor too their treatment(eg.stretching, joint mobilisation,massage)

15

Clinical Scenarios for Using Heat

• Generally avoided in acute phase ?potential for increasing bleeding
• Sub‐acute – chronic musculoskeletal conditions e.g. osteoarthritis
• Following immobilisation for extended periods e.g. fractures • Prior to other Rx

16

EPAs that produce heat

• Superficial heat
• Hydrocollator/Hot packs (HP)
• Wax
• Aquatic therapy/hydrotherapy
• Deep heat
• Ultrasound (US)
• Shortwave diathermy (SWD)
• Microwave (MW)
• Radiant heat
• Heat lamps, infrared, ultraviolet (not used much these days)