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Physical Agents > Principles of thermal energy: Thermotherapy > Flashcards

Principles of thermal energy: Thermotherapy Flashcards

1
Q

Thermal regulation

A

Humans are homeotherms

  • we are able to maintain our core temp at a constant
  • generally normal core temp is 98.6 degree F
  • Can vary due to :
  • diurnal changes: lower core temp in am vs pm
  • the outside surface of the body can be referred to as shell
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2
Q

Thermal kinetic energy

A
  • the movement of molecules or their components is related to the temp of a substance
  • as the temp of a substance increases its molecules move more rapidly
  • kinetic energy is thermal energy
  • heat- energy in transit from high temp object to low temp object
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3
Q

thermal potential energy

A
  • Energy of position
  • molecules are attracted to one another by forces. The energy associated attraction is potential energy
  • remains constant so long as the phase of matter doesn’t change
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4
Q

Phase change

A
  • Change from one state to another
  • always occur with a change of heat
  • solid> liquid
  • occurs without a change in temperature
  • changes in potential energy
  • attraction forces within an object are relaxed
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5
Q

Latent heat of fusion

A

Amount of heat required to convert a certain unit of a solid into a similar unit of a liquid without changing temperature

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6
Q

First law of thermodynamics

A

With the exception of nuclear effects energy can be neither created nor destroyed but is transformed from one form to another.
- whenever this transformation occurs some energy is released as heat and is considered thermal energy

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7
Q

Specific heat

A
  • the amount of energy required to raise the temp of a given material by a specific number of degrees
  • different materials (thermal agents or body tissues) have different specific heats
  • materials with high specific heat require more energy to achieve an equivalent increase in temp than materials with a low specific heat
  • material with high specific heat hold more energy than materials with a low specific heat when both are at the same temp
  • water has a very large specific heat
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8
Q

Specific heat of paraffin

A

0.65

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9
Q

specific heat of water

A

1.0

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10
Q

modes of heat transfer

A
  • conduction
  • convection
  • conversion
  • radiation
  • evaporation
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11
Q

Conduction

A
  • exchange of energy between 2 materials at different temps due to the direct collision of molecules of the materials
  • the molecules of the higher temp material move faster
  • they collide with molecules of the cooler material causing them to accelerate
  • heat will continue until speed of molecular movements become equal
  • for heat transfer to occur the two materials must be in direct contact with each other
  • subcutaneous tissues are heated by conduction of energy through adjacent layers
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12
Q

Rate of heat transfer (ROHT) by conduction depends on:

A
  • temperature difference between materials
  • their thermal conductivity
  • the area in contact
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13
Q

Rate of heat transfer (ROHT) equation

A

ROHT= area of contact x thermal conductivity x temp diff/ tissue thickness

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14
Q

Guidelines for heat transfer by conduction

A

-The greater the temp difference between the two materials the faster the rate of heat transfer (make ice from hot water vs cold)
- materials with high thermal conductivity transfer heat faster than materials with low thermal conductivity
-

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15
Q

Conduction: hot pack

A
  • hot pack kept in water approx 155-165 degree F
  • high temp, high specific heat, and moderate thermal conductivity of water allows efficient heat transfer to pt
  • but temp difference may be large enough that patient may become uncomfortable or even burned
  • dry towels that trap air placed between hot pack and pt will limit the rate of transfer of energy
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16
Q

Conduction modalities application considerations

A
  • metal has high thermal conductivity and may heat rapidly and burn pt
  • the larger the area of contact between two materials the greater the heat transfer
  • the rate of tissue temp rise decreases in proportion to tissue thickness
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17
Q

Convection

A
  • Transfer of heat as the result of direct contact between circulating medium and another material of a different temp
  • thermal agent is in constant motion
  • new parts of the thermal agent (@ the initial temp) keep coming in contact with the material to be heated/ cooled
  • transfers more heat/time than conduction
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18
Q

Convection examples

A
  • Whirlpool
  • Fluidotherapy
  • blood: transfers heat by convection to protect local tissue
  • oven
  • central air conditioning
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19
Q

Conversion

A
  • Converting a non thermal form of energy into heat
  • mechanical: ultrasound, friction
  • chemical: acid to metal> heat (chem heat pack)
  • rate of heat transfer depends upon the power of the energy source
  • rub hands together faster> increased heat
  • does not require direct contact
  • does required a good conductor of energy
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20
Q

Radiation

A

-Direct transfer of energy without direct contact or intervening medium

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21
Q

radiation rate of temp increase depends on:

A
  • intensity of radiation
  • relative size of the radiation source
  • relative size of the radiation area
  • the distance of the source to the target tissue
  • the angle of the radiation source to the target tissue
22
Q

Radiation examples

A
  • infrared lamp

- ultraviolet light

23
Q

Evaporation

A
  • A material must absorb energy before it can evaporate

- example: vapocoolant spray

24
Q

Thermotherapy

A
  • The therapeutic application of heat
  • used outside rehab to :
  • destroy malignant tissue growth
  • treat cold related injuries
  • Used in rehab to provide:
  • hemodynamic effects
  • neuromuscular effects
  • metabolic effects
  • altered tissue extensibility
25
Q

Thermotherapy: hemodynamic effects, Vasodilation

A

-Vasodilation: application of heat increases diameter of BVs and thus increase in rate of blood flow

26
Q

Thermotherapy: hemodynamic effects, stimulation of cutaneous thermal receptors

A
  • reflex activation of smooth muscles in blood vessels causing dilation (direct)
  • increased production and release of histamine, bradykinin, prostaglandins, and nitrous oxide
  • vasoactive mediators directly stimulate the smooth muscles in BV wall
  • stim of cutaneous thermal receptors project through dorsal root ganglion to synapse on interneurons in dorsal horn of spinal cord
  • these interneurons synapse with sympathetic neurons in lateral horn of thoracolumbar segments of spinal cord
  • this causes inhibition of sympathetic activity
  • causes reduction of smooth muscle contraction
  • generally not in skeletal muscle when applied superficially
  • acts to protect body from excessive heating and tissue damage
  • increased blood flow removes heat via convection
27
Q

Thermotherapy: neuromuscular effects, increased nerve conduction velocity

A
  • for each 1.8 degree F ( 1 degree C) increase in temp, NCV may increase by approx 2m/sec
  • increase muscle temp to 108 degree F (42 C)
  • decreased firing rate of type II muscle spindle efferents and gamma efferents
  • increased firing rate of type 1b fibers and GTOs
  • results in decreased firing rate of alpha motor neurons> decrease in muscle contraction (spasm)
28
Q

Thermotherapy: neuromuscular effects, increased pain threshold

A
  • directly by activation of spinal gate

- indirectly by reduction in ischemia and muscle spasm and facilitation of tissue healing

29
Q

Thermotherapy: neuromuscular effects, in demyelinated peripheral nerve

A
  • heat shortens time Na+ channels are opened at node of ranivier
  • this decreases conduction time and effects end organ of that nerve
30
Q

Thermotherapy: neuromuscular effects, changes in muscle strength

A
  • decreases during the first 30 mins after superficial or deep heating
  • decreased firing rate of type 1a muscle spindle efferents and gamma efferents
  • increased firing rate of type 1b fibers and GTOs
  • results in decreased firing rate of alpha motor neurons> decrease in muscle strength
  • for next 2 hours strength returns then increases to above preintervention
31
Q

Metabolic effects

A
  • increases endothermic chemical reaction rate including enzymatic biological reactions
  • from 102 degree F to 109 degree F (39-43 C) reaction rate increases 13% for every 18 degree F rise in tissue temp
  • beyond 113 degree F enzyme activity begins to decrease and ceases at about 122 degree F
  • heat increases oxygen uptake and accelerates healing
  • heat increases activity of collagenase which may increase destruction of articular cartilage in RA
  • heat shifts oxygen-hemoglobin dissociation curve to right-makes more oxygen available for healing
32
Q

Thermotherapy: altered tissue extensibility

A
  • decreases fluid viscosity
  • decreases joint and muscle stiffness
  • relaxes cross-linked collagen fibers
  • increase tissue temp to 104 to 113 degree F for 5-10 mins> plastic deformation
33
Q

Uses for thermotherapy

A
  • pain control
  • increased ROM and decreased joint stiffness
  • accelerated healing
34
Q

Types of thermotherapy

A
  • moist hot packs
  • paraffin bath
  • infrared lamps
35
Q

Moist Hot packs

A

Infrared modality emitting electromagnetic radiation
- wavelength is equal to approx 82,457
- frequency= 3.63 x 1012 Hz
Thermal modality used for superficial heating of tissue
- maximum depth of heat penetration= 1 cm
- heat tissues via conduction
* energy exchange by direct collision between molecules of two materials at different temps

36
Q

Moist hot pack general description

A
  • packs made of canvas and filled with silica gel
  • generally heated in hydrocollator to 160 degree F for at least 20 mins prior to heating
  • capable of retaining heat for approx 20 minutes
37
Q

Moist hot pack, paraffin bath, and infrared lamp therapeutic purposes & goals

A

To heat tissues to therapeutic level
- 105.8 to 113 degree F
- occurs in about 8 to 10 mins
- the bodies physiological response to heat stimulus may be therapeutic
-within 30 mins of superficial heat application the body reaches thermal equilibrium and further heating is not beneficial
primarily used to provide analgesia and reduce pain
increase ROM & decrease joint stiffness ( relax local structures)
accelerate healing

38
Q

Moist hot pack, paraffin bath, & infrared lamp physiological effects

A
  • Muscle relaxation via effects on muscle spindles and GTOs
  • sedation of sensory nerve endings if heat is mild enough
  • increased capillary pressure & cell permeability
  • increased extensibility of CT with stretching exercises
  • increased body temp, pulse rate, & decreased blood pressure (?)
39
Q

Moist hot pack, paraffin bath, and infrared lamp indications

A
  • impairments associated with sub acute and chronic conditions ( OA, muscle injury, muscle guarding, etc)
  • tissue contractures/adhesions
  • joint stiffness
  • stimulation of perspiration to improve electrical stim
40
Q

Moist hot pack, Paraffin bath, & infrared lamp contraindications/ cautions

A
  • acute inflammatory disorders (sprains, strains)
  • previously existing fever
  • malignancies (cancer) in tx area
  • active bleeding in tx area
  • pts with cardiac insufficiency
  • older pts and children under the age of 4
  • pts with peripheral vascular disease (PVD)
  • previously existing edema
  • tissues devitalized by x-ray therapy
41
Q

Moist hot pack advantages

A
  • relatively safe in that MHPs cool over time

- may effectively treat local areas

42
Q

Paraffin baths

A

Infrared modality emitting electromagnetic radiation
- wavelength approx = to 90,187
- frequency approx= to 3.32 x 10^12 Hz
thermal modality used for superficial heating of tissue
- maximum depth of penetration is = to 1 cm
- heats tissues via conduction

43
Q

Paraffin bath description

A
  • tank containing a mixture of medial paraffin wax and mineral oil
  • the two ingredietns are mixed in a ratio of approx 5 lbs of wax to 1 pt of oil
  • tanks generally have a heating unit & a thermostat that keeps the melted wax at about 125-127 degree F
  • pt areas to be treated are immersed in this heated mixture
  • the specific heat of paraffin is low
44
Q

Paraffin baths advantages

A
  • useful in treating chronic orthopedic conditions of the distal extremities
  • aids in softening of the skin
45
Q

Paraffin bath disadvantages

A
  • provides six times the amount of heat in water thus risk of burn is substantial
  • paraffin treatment can be messy
  • cleaning of the tank can be difficult
46
Q

infrared lamp

A

Infrared modality emitting electromagnetic radiation
- wavelength= to 770 nm to 1mm, IR-A wavelength = 770 to 1400 nm
- frequency= 3.63 x 10^12
Thermal modality used for dry superficial heating
- maximum depth of penetration= 1 cm
- generally absorbed within the first 1-3 mm of tissue
-heats tissues via radiation
* energy exchange by direct collision of molecules of two materials at diff temps

47
Q

Infrared lamp classification:

A 
IR-A (short or near IR) 
- most common
- wavelengths between 770 to 1400 nm
-generated by luminous lamp
IR-B (middle IR)
- wavelengths between 1400 and 3000 nm
-generated by nonluminous lamp
IR-C (long or far IR)
-wavelengths betweeen 3000 to 10^6 nm
-generated by nonluminous lamp
48
Q

Infrared lamp description

A
  • A lamp or baker that generates infrared radiation that produces heat when absorbed by matter
  • TTR proportional to :
    • amount of radiation absorbed
    • the power and wavelength of the source
  • the distance of the source to the tissues (inverse sq law)
  • the angle of incidence of the radiation (cosine law)
  • the absorption coefficient of the tissue
  • most lamps deliver power in range of 50-1500 watts
  • clinically used wavelength is 780 to 1500 nm
  • absorbed within first 1-3 mm of human tissue
  • human skin allows maximal penetration at wavelength of 1200 nm
  • IR radiation absorbed best by tissues with high absorption coefficient
    • dark skin has higher absorption coefficient therefore will increase in temp greater than light skin
49
Q

Luminous lamp

A
  • heat produced by resistance to an electric current as it passes through a tungsten or carbon filament surrounded by metal reflectors
  • produces visible, bright white light (IR-A)
  • power output 60-1500 watts
  • no warm up period needed
50
Q

Infrared lamp advantages

A
  • does not require direct contact with the pt

- can see the area being treated during session

51
Q

Infrared lamp disadvantages

A
  • ensuring uniform heating is difficult
  • glare may irritate pt’s eyes
  • hard to localize tx area
52
Q

Reasons for intervention

A
  • to increase local blood flow
  • to relax muscle spasm
  • to increase tissue temp
  • to increase local tissue extensibility
  • to modulate pain
  • to promote tissue healing

Physical Agents (21 decks)

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