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Physical Agents > Heat > Flashcards

Heat Flashcards

1
Q

What 5 things do the biophysical effects of temperature elevation depend on?

A
  • the extent of temperature rise
  • rate energy is added to tissue
  • volume of tissue exposed
  • composition of absorbing tissue
  • capacity of tissue to dissipate heat
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2
Q

What temp do you have to get tissue at or above in order to reach therapeutic levels?

A

100 degrees F (40 degrees C)

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3
Q

what is skin temp typically?

A

98
want to get above that

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4
Q

what skin temp is “feeling cool”

A

96 or below

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5
Q

signs of heating

A

redness
swelling
sweating

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6
Q

what is one of the mechanisms that rises skin temperature?

A
  • blood flow
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7
Q

when skin is getting warm, what does blood do?

A

starts flowing with cooler blood

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8
Q

what occurs if you add heat too fast

A

the blood cant keep up with cooler blood and results in a burn

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9
Q

do all tissues have the same rate of warming?

A

nope

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10
Q

what makes a difference in heating

A

the rate of application

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11
Q

the larger the area you heat…

A

the more likely you are going to get a systemic effect

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12
Q

Composition of absorbing tissue

A
  • how much fat is there? it will be a barrier to getting heat down to muscle
  • what is composition of that area of tissue
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13
Q

capacity of tissue to dissipate heat

A
  • heat on people with peripheral vascular disease or arterial disease should be used with caution
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14
Q

4 physiologic responses to heat

A
  1. metabolic reactions
  2. hemodynamic techniques
  3. neuromuscular response
  4. connective tissue effects
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15
Q

how much does metabolic reaction increase for each ten degrees Celsius?

A

2-3 times

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16
Q

at what temperature is increased enzymatic activity observed?

A

40 degrees Celsius / 102-109 F
lend to therapeutic significance

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17
Q

what temp is scalding

A

120 F

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18
Q

why does tissue burn occur

A

due to metabolic activity required to repair
tissue not being capable of matching protein denaturation

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19
Q

what increases with heat, promoting tissue healing?

A

oxygen uptake
even with mild temperatures
happens greater with higher elevations

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20
Q

take home message for metabolic reactions

A

if you dont have enough heat, it won’t increase the metabolic activity enough to make a change BUT dont increase it too much or too fast

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21
Q

what hemodynamic effect does heat cause?

A

vasodilation –> increased blood flow

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22
Q

Direct Axonal Reflex (neural)

A

 Heat applied to skin stimulates cutaneous
thermoreceptors
 These sensory afferents carry impulses to the
spinal cord
 Some of these afferents are carried toward the
skin blood vessels, causing release of a
vasoactive mediator
 Leads to vasodilation through an axon reflex

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23
Q

Spinal Cord Reflex

A
  • decreased sympathetic nerve activity to smooth muscle of blood vessels
  • probably the biggest thing that is happening
  • Most things that are happening are going up to the spinal cord saying “open up, we need cold blood to the area”
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24
Q

chemical mediators released from heat

A

histamine and prostaglandins

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25
Q

what does sweat secretion produce

A

an enzyme called Killikren

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26
Q

does what killikren do?

A
  • acts on globulin and kininogen to release Bradykinin and nitrous oxide which then acts on smooth muscle and endothelial cells of
    contractile structures
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27
Q

what occurs to permeability with heat?

A

here is an increase in permeability in capillary and post capillary venule due to the action of the chemical mediators on the endothelial cells

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28
Q

what occurs due to increase in capillary pressure?

A
  • outward fluid filtration from vascular to extravascular space can occur
  • Mild inflammation –> little bit is normal but sweating occurs first
29
Q

shunting

A

When overheating occurs, branches of the
peripheral system which were bringing blood to the
area may constrict shunting the blood to the
periphery

30
Q

clinical implication for hemodynamic effects?

A
  • due to increased blood flow, there should be some redness and possible mild swelling
  • when moving blood out, there could be some inflammation in the periphery (be careful!)
31
Q

neuromuscular response to heat

A

Heat can elevate the pain threshold, alter nerve conduction velocity and change muscle spindle firing rate

32
Q

How does heat affect pain?

A

 Decrease underlying muscle spasms
 Counterirritant
 Gate theory (maybe stimulating aBetas)
 Still under investigation –> heat is rarely getting to the muscle yet we’re still seeing changes

33
Q

How does heat affect muscle spasms?

A

 Type II afferent firing decreases and firing of Ib fibers increases
 Decrease firing of alpha motorneruons leading to decreased extrafusal fiber activity (1b fibers coming off GTOs) CANT PRODUCE AS MUCH STRENGTH
DONT PUT HEAT ON FIRST

34
Q

another theory on how heat affects muscle spasms

A

gamma Efferents: heat decreases the firing of the muscle spindle via gamma efferents

35
Q

DOMS

A

 Moist heat more effective than heat wraps and chemical wraps
 Heat wrap PRIOR to exercise  45%-52% decrease pain, disability and improvement in self-reported physical function
 138% greater pain relief for 24 hours postexercise

36
Q

Neural Clinical Implications

A
  • positives: pain threshold is addressed; promotes relaxation
  • use of heat to resolve pain is not well understood
  • nonetheless, heat does appear to alter pain perceptions
  • multiple ways to decrease muscle spasm via changes in nerve conduction velocity
  • potential downside: can effect strength
37
Q

what occurs to collagen at 50 C

A

collagen shrinks and dematerializes

38
Q

what occurs to tendons at 41-50 C?

A

they show a different behavior
 450C, water properties become dominate
 If temperature is elevated, but no load applied there is no residual elongation (have to heat AND stretch)
- changes the structural soundness of tissue (stress/strain curve)
- stiffness is decreased

39
Q

As far as the stress/strain curve goes, heating the tissue =

A

less force, more elongation
(more deformation with less load)

40
Q

Clinical implications of connective tissue affects of heat?

A
  • superficial tendons and scar tissue most likely tissues affected
  • if you want to maintain the stiffness of the tissue, heat is a bad choice (dont heat ligaments)
  • tissue needs to be stretched WHILE heat is applied
41
Q

therapeutic effects of heat

A

 Increases the extensibility of collagen tissues
 Decreases joint stiffness
 Produces pain relief
 Relieves muscle spasms
 Assists in resolution of inflammatory infiltrates, edema, and exudates

42
Q

how long should you apply heat

A

8-10 minutes
not much change after that

43
Q

Factors that influence heat exchange

A
  1. Conductivity of material
  2. Intensity of Heat Supply*
  3. Time of Exposure*
  4. Gradient between thermal agent and material being heated
44
Q

conduction

A

 Kinetic motion of atoms and molecules of one object get
passed to another
 Total heat transfer with conduction is dependent on: time of flow, temperature gradient, treatment area, and thermal conductivity (all directly proportional)

45
Q

Convection

A

 Bulk movement of moving molecules, in liquid or gaseous form, from one place to another
- transfer of heat by movement of air or liquid around the object to be heated
- little bit more heat transfer with this rather than conduction
- contact is not constant like conduction
- ask Daniela the last bullet here

46
Q

Radiation

A

 Conversion of heat energy to electromagnetic radiation
 All objects above –2730C (absolute 0) emit and absorb radiant energy
- not the biggest form of transfer but always there

47
Q

Superficial heating agents

A

 Hot Packs
 Paraffin Wax
 Fluidotherapy
 Hydrotherapy
 Radiant Heat
 Moistaire Cabinets

48
Q

what is a hot pack

A

 Canvas or nylon case filled with hydrophilic silicate or sand

49
Q

what temp of water is a hot pack kept in?

A

158-167 F (70-75 C)

50
Q

when is greatest tissue temp increase seen with a hot pack?

A

after 8 minutes with reduction after that time secondary to increase in blood flow and cooling of the hot pack

51
Q

what occurs if you repeat the application of a hot pack (change the pack)

A

may increase the time of heating effects, but does not significantly change tissue temperature

52
Q

are deep tissues affected from hot packs?

A

usually not affected secondary to heat transfer
from skin to the deep tissue is inhibited by subcutaneous fat

53
Q

clinical implications of hot pack- Advantages

A
  • easy prep and application
  • variety of sizes
  • positioning
  • home applications
54
Q

clinical implications of hot pack - disadvantages

A
  • no temp control (poor heat retention)
  • poor conformity
  • hard to secure sometimes
  • passive patient environment
  • tank maintenance
55
Q

what is paraffin wax mixed with?

A

paraffin oil or mineral oil (5-7:1)

56
Q

what does oil do to the wax

A

Oil decreases its melting point (54 C); wax remains molten between 45-54C

57
Q

what does molten state of wax allow?

A

even distribution of wax around area
being treated

58
Q

somethings about wax

A

 Wax has a low specific heat and therefore feels less hot than water at the same temperature; also decreases risk of burn with greater temperature
 Conducts heat more slowly than water, allowing more gradual buildup of heat lending to decreased risk of burn; also tolerated better by patient
 Heat is conducted from the layer of solid wax on the skin

59
Q

types of application of paraffin wax

A
  • dip wrap
  • dip re-immersion
60
Q

dip wrap

A

multiple layers of wax wrapped with insulated towels (is it 8 times??)

61
Q

dip re-immersion

A

dip 1-2 times for a protective later then leave the body part in the wax mixture for remaining treatment

62
Q

advantages of paraffin wrap

A
  • apply at a higher temperature without burn
  • contours to body part
  • increase skin moisture
  • home use
63
Q

disadvantages of paraffin wrap

A
  • only useful on distal parts of extremities
  • no temp control
  • passive
  • some wax reusable
64
Q

Fluidotherapy

A

 A bed of finely divided solids (glass beads with an avg diameter of .0165”, or finely ground corn cob called “cellex”) through which thermostatically controlled heated air is blown to produce a warm semifluid mixture to which the body can be exposed
 The solid particles become suspended when air is blown into them, and the particles behave as a liquid
 Permits movement of the body part due to the low viscosity

65
Q

temperature ranges of fluidotherapy

A

38.3 - 47.8 C

66
Q

clinical applications of fluidotherapy- advantages

A

heat control
can have activity
desensitization

67
Q

disadvantages of fluidotherapy

A

claustrophobia
no home application
$$$

68
Q

advantages of hydrotherapy

A
  • conformity
  • exercise
  • desensitization
  • other principles of water
69
Q

disadvantages of hydrotherapy

A
  • $$$
  • positioning
  • possible systemic reactions
  • fear of water

Physical Agents (11 decks)

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