Superficial Heating Modalities

Lecture 7Dr. Afaf Ahmed Shaheen

2

Outlines

Factors affecting magnitude of physiologic effects

Physiological effects Indications Contraindications

3

5 Mechanisms of Energy (Heat) Transfer in the Body: Added or Removed

Conduction – transfer of heat through the direct contact between a hotter and a cooler area (2 objects touching each other)– Ice Massage, Hydrocollator Pack, Ice Pack

Convection – transfer of heat by the movement a medium (air, liquid) between regions of unequal temperature– Whirlpool

Conversion – energy is changed from one form to another; does not relate to superficial heat or cold– Electrical energy into heat, Acoustical energy into heat– Ultrasound, Diathermy

4

Radiation – emitted from surfaces with temperatures above absolute 0° (all atomic & molecular motion ceases)– Transfer of energy without the use of a medium– Body, Sun, Infrared lamp, LASER, Ultraviolet

light Evaporation – change from liquid state to

gaseous state requiring thermal energy be removed from the body– Vapocoolant Spray

5

Superficial Heating Modalities Therapeutic application of heat is known as thermo-therapy

Used to heat joints with little soft-tissue covering

Heating deeper structures through reflex mechanisms.

Therapeutic heat………40ºC to 45ºC More than45ºC………….tissue damage. Less than 40ºC………….mild heating. 

6

Biophysical Effects (physiologic effects)

Factors affecting magnitude of physiologic effects:Extent of temperature rise

•Temp. must be elevated 40-45oCRate at which energy is being added to

tissue•Very slow: heat balanced by cooler blood•Very fast: stimulates pain receptors

Volume of tissue exposed•Larger tissue area affected: systemic

reaction

7

   

1)Hemodynamic effect (effect on vascular bed)

 Dilatation of the blood vessels

(vasodilatation) leads to hyperemia and sweating.

a)Direct reflex activation of smooth muscles of blood vessels by cutaneous thermoreceptors.

b) indirect activation of spinal cord reflexes by cutaneous thermoreceptors or by increasing the local release of chemical mediators of inflammation (histamin+prostaglandin).

 

8

Effects on Blood Flow Vasodilatation: blood flow

– Response to temp. change not always the same:• Skin blood flow: maintenance of constant

body core temp. under sympathatic adrenergic nerves

– Has arteriovenous (AV) anastomoses, important for heat loss (bypass capillary bed), triggered by heated blood through anterior hypothalamus

• Skeletal-muscle blood flow: metabolic regulation with greatest response to level of exercise

– Minimal or no change in blood flow

9

10

With maximal vasodilatation there are

Rise in pulse rates. Drop in blood pressure Profuse sweating with chloride

loss Increase fluid transfer across the

capillary wall with increased removal of tissue metabolites

11

Neuromuscular effects 1On muscles:

a) Relaxation: ·    This occurs when the warm blood

reaches deeper and deeper into the muscles causing the vessels to expand.

·        Relaxation relieve of pain by easing any pinching of nerves or blood vessels and by helping the muscles to remove lactic acids and other metabolic wastes.

·        Relaxation in ROM allowing for gentle exercises and stretching.

b)    Increase blood flow·        Heat increase blood

flow in the muscles this is beneficial in muscle spasm or sustained contractions where ischemia may contribute to the pain.

2) On nerve Analgesia on the

peripheral and central nervous system.

Sedative action: as the body tries to register a temperature change, the central nervous system becomes depressed, contributing to muscle relaxation and temporarily relieve of pain.

The thermal stimulus that affects the pain sensation is explained by the gait control theory of pain.

12

Neuromuscular Effects

Heat used to reduce spasm:

– Elevation of pain threshold sensory nerve-conduction velocity

– Change in muscle spindle firing rate (gamma afferent fibers)

– Muscle strength and endurance?

13

Change in muscle strength

1) Decrease in the initial 30 minutes after the application of superficial and deep agents due to

• change in the firing rates of type II muscle spindle efferent,

• gamma efferent • and type Ib fibers from golgi tendon organs.

2) Beyond 30 minutes after the application of heat and for the next 2 hours, muscle strength gradually recovers and then increase to above pretreatment levels.

14

Effects on Connective Tissue

Temperature elevation + Stretch: change viscoelastic properties of connective tissues

Heating decreases joint stiffness and increase tissue extensibility.

Length change with damage: stretch + heat

15

On the whole body and metabolism

Rise body temperature. Increased pulm onary ventilation. Increased metabolism: 10 ºC

increase in the temperature will twice or triple the metabolic rate leading to an increase of oxygen uptake, an increase of nutrients and promotion of healing.

16

Effects on Metabolism

Metabolic rate 2-3 times for each 10 oC energy expenditure oxygen uptake nutrients: healing

17

Reflex effect of prolonged heat 1. Prolonged heat to one extremity

causes vasodilatation of the contra-lateral extremity.

2. Prolonged heat to the abdominal wall causes a decreased in the intestinal blood flow, diminish in the intestinal motility and decrease in the secretion of acid in the stomach.

3. Prolonged heat to the pelvis relaxes the musculature of the pelvic organs, dilates the blood vessels and increases menstrual flow.

18

Reflex effect of prolonged heat 4. Prolonged moist heat to the chest

promotes ease of respiration and expiration.

5. Prolonged heat to the trunk, such as a hot trunk pack, relaxes the ureters or bile ducts and relieves renal or gallbladder colic.

6. Prolonged moist heat to the area over the kidneys in the back and over the lower abdomen in front increases the production of urine.

19

Thermotherapy Effects Local Effects

metabolic rate

– Vasodilation capillary permeability nerve conduction

velocity pain muscle spasm

– Edema formation

Systemic Effects body temperature pulse rate respiratory rate blood pressure

20

Question:

Compare between the effects of cold and heat in terms of their biophysical effects.

21

Indications

Reduction of pain– Before exercises

Alleviation of muscle spasm Increase range of motion Improve tissue healing (increase blood flow

& nutrients) Temperature: 40-45oC Duration: 20-30

22

Contraindications

Sensitivity to temperature and pain Circulatory impairment (arterial disease) Likelihood of bleeding or hemorrhage (e.g.

hemophilia, postacute trauma, long term steroid therapy)

Acute injury or inflamation Impaired sensation Malignancy - thrombophebitis

23

Precautions Pregnancy Impairment circulation Poor thermal regulation Cardiac insufficiency Metal in the area Over an open wound Over areas where topical counterirritants have

recently been applied Edema

24

Conductive heat agents Hot packs

– Superficial moist heat– Canvas cases filled with hydrophilic silicate – Stored in thermostatically controlled cabinet

in water at temperature ~ 71.1 oC– Wrapped in toweling before application (6-8

layers)– Should feel mild to moderate sensation of

heat– Between treatments pack returned to unit

and completely immerse in hot water (30 min)

– Come in sizes and shapes

25

Conductive heat agents

Paraffin wax

– Melting point 45.5oC stay liquid at temperature more than 47.8oC when mixed with mineral oil in a 6:1 or 7:1 ratio of paraffin to oil

– 2 techniques: dip & wrap OR dip & reimmerse

26

Case Study

A 25-year old female is seen in physiotherapy 8 weeks following reduction and casting of a right Colle’s fracture. The cast was removed yesterday. There is mild swelling on the dorsum of the hand. Range of motion of the wrist is limited in all planes. Metacarpophalangeal flexion is reduced in all digits. Pain is present on active and passive motion but not at rest

27

Convective Heating: Fluidotherapy Convection: heat transfer

in which the heated molecules move from one place to another

Fluidotherapy: – dry heat agent transfer

energy by forced convection

– Warm air circulated through a container holding fine cellulose particles

28

Radiant heating: Infrared lamps

Radiation:

Increase in infrared energy causing the molecular motion in the cooler object to increase, thus increasing heat.

29

Regulation of body temperature

1) The rate of heat production usually balances the rate of heat loss.

2) The thermostatic control of temperature occurs in neural centers in the spinal cord and in the hypothalamic region.

3) Reflex and semi-reflex thermoregulatory centers include autonomic, somatic, endocrine and behavioral patterns.

4) Reflex responses activated by the cold are controlled from the posterior hypothalamus, while those activated by warmth are controlled from anterior hypothalamus