Physiological Properties Of Thermal Effects Flashcards
What is Thermotherapy
Application of heat source (thermal agent) over skin surface areas for the purpose of heating SUPERFICIAL and DEEP soft tissues
Thermotherapy is rested on heat transfer from the _________ to the _____________________
Thermal agent
Biological tissue
Two types of heat produced and how they are delivered
1- Moist heat
- hot packs
- paraffin baths
2- Dry heat
- fluidotherapy
- SWD (short wave)
- US (ultrasound)
Thermotherapy has been classified as
1- superficial Thermotherapy
2- deep Thermotherapy
Difference between superficial and deep Thermotherapy
Superficial : heating of soft tissue located within 1 cm from skin surface
Deep: heating of soft tissue deeper than 1 cm from skin surface
What is thermodynamics
Branch of physics concerned with the relationship between heat and other forms of energy
Laws of thermodynamics
First law - energy is neither created nor destroyed, it only changes from one form to another or transfers from one object to another
Second law- heat energy transfer occurs in ONE direction (warmest to coolest)
What is the first law of thermodynamics also called
Law of conservation of energy
Which thermodynamic law is the law of conservation of energy
First law
What is heat
Heat is a form of energy. It is the total kinetic energy or molecular motion of a substance
Heat is interchangeable with other forms of energy such as ….
Electrical energy
Mechanical energy
The greater the molecular motion of a substance, the ________ heat it contains
More
_________ is a unit of heat
Calorie
It says in the slides “heat unit is calorie” but im pretty sure the SI unit for heat is Joules ….
What are thermophysical properties
Specific heat capacity (C)
Thermal conductivity (K)
What is specific heat capacity (C)
The amount of heat energy (in calories) required to increase the temperature of 1g of a substance by 1 C.
It is the ability of a substance to store heat
Unit of specific heat capacity
Cal/gC
The higher the specific heat capacity of a substance, the __________ its capacity to store heat
Higher
What is thermal conductivity (K)
The heat needed to increase the temperature of 1g of a substance by 1C
The ability of a substance to conduct heat
The higher the thermal conductivity of a substance, the _______ its ability to conduct heat.
Better
Why must jewelry be removed during Thermotherapy ?
Metal and carbon are great conductors due to their high thermal conductivity and high specific heat capacity
Why should we be careful when using Thermotherapy on obese patients ?
Because subcutaneous fat absorbs and stores heat well (good specific heat capacity)
The specific heat of wax (0.45) < of water (1.0) and the thermal conductivity of wax (0.59) < of water (1.42)
Modes of heat transfer
Conduction
Convection
Radiation
Evaporation
What is conduction
Heat transferred by physical contact between two solid substances of different temperature
Conduction occurs from the __________ to the _________ substance
Warmest
Coldest
Thermotherapy examples of conduction
Hot packs
Paraffin wax
Cold packs (cryotherapy)
Guidelines for heat transfer by conduction
- The GREATER the temperature difference between agent and body part = the FASTER the rate of heat transfer
- Materials with HIGH thermal conductivity = transfer heat FASTER than those with lower conductivity
What is convection
Transfer of heat through fluid or gas caused by its molecular motion
It occurs through physical contact between a gas or fluid medium and a solid substance both at different temperatures
Heat transfer by circulation of a medium of a different temperature is ……
Convection
Examples of convection
Fluidotherapy
Hydrotherapy
Boiling water is what form of heat transfer
Convection
What is radiation
DIRECT transfer of heat energy in space between the emitting source at one temperature and the absorbing medium at a different temperature
Examples of radiation
UV (ultraviolet)
SWD (short wave)
LLLT (low level laser therapy)
Rate of temperature increase by radiation depends on:
- intensity of radiation
- side of radiation source
- distance
- angle of radiation source
Cosine and inverse square laws refers to the ……
Angle of radiation source
What type of mode of heat transfer is this
Radiation
What is evaporation
The transformation of a material from a liquid to a gas
Example of evaporation
Vapocoolant sprays
What is temperature
The measure of the level of heat
The great the amount of heat in a substance = the ___________ its temperature
Higher
Temperature is measured by which scales
Celsius (C)
Fahrenheit (F)
0 Celsius = ? Fahrenheit
0 C = 32 F
100 Celsius = ? Fahrenheit
100 C = 212 F
What is the unit of temperature
Kelvin (K)
0 Celsius = ? Kelvin
0 C = 273.2 K
100 Celsius = ? Kelvin
100 C = 373.2 K
Two compartments for body temperature
The core compartment
- controlled by the physiological mechanisms at constant level
- around 37 C but even more in organs
The shell/ superficial layer
- subject to much greater variations in temperature
The temperature of the shell/ superficial layer varies according to:
- core temperature
- external environment
How to take body temperature measurement
Thermometers
What is skin thermal discrimination test
Ruffini and Krause’s bulb
Receptors sensitive to heat and cold information from skin and deep tissues
Role of hypothalamus involving temperature
It monitors heat balance of body and prevents any deviation of core temperature
Which center is for heat loss
Pre-optic center
Which center is for heat gain
Post-optic
Pre-optic center
Heat loss
Post-optic center
Heat gain
Physical effects of heat
- increases kinetic energy of molecules
- increase expansion of materials
- change in physical state of material
- acceleration of chemical reactions
- reduction in viscosity of fluids
Why does heat cause expansion of materials
The increase in kinetic energy causes an increase in vibration of molecules
Changing substance from one physical state to another requires a specific amount of heat energy
This heat energy is called
Latent heat
Heat causes acceleration of chemical reactions.
What law states this?
Van’t Hoff’s Law : any chemical reaction capable of being accelerated is accelerated by a rise in temperature
Thermophysiological effects of heat
- Haemodynamic effects
- vasodilation
- increased metabolic rate - Neuromuscular effects
- increased nerve conduction velocity and firing rate
- increased pain threshold
- decreased muscle spasm - Altered tissue extensibility
- increase collagen extensibility
What does heat do to blood
Lowers the viscosity and increases blood flow along with vasodilation
Why does heat increase metabolic rate
- increases rate of chemical reaction / enzyme activity
- increases rate of cellular biochemical reaction (phagocytosis and growth)
- increases oxygen uptake
- increases tissue healing
How does heat increase the pain threshold thus reducing pain?
Directly through gating
This is based on the Gate Control Theory of Pain, which suggests that there is a gating system in the CNS that opens and closes to let pain messages through the brain or block them.
How does heat decrease muscle spasm
Decrease alpha and gamma motor neuron activity
How does heat increase collagen extensibility
Changes organization and viscoelasticity of collagen fibers
Therapeutic effects of superficial heating
- Pain control
- Increased ROM and decreased joint stiffness
- Accelerates healing
How does heat control pain
Directly through gating
Indirect due to improve healing (reducing muscle spasm)
Explain how gating reduces pain
Stimulation of heat receptors and vascular changes will wash out pain provoking metabolites
Heating is not recommended for
Acute inflammation
How does heat increase ROM and decrease stiffness
- Increase collagen extensibility
- analgesic effect
- decreases joint viscosity
- increases tissue elasticity
What to use for superficial stretching
Hot pack
Paraffin wax
IR (infrared therapy)
For deep stretching use :
Ultrasound
Short wave SWD
How does heat accelerate healing
-Increases circulation (provides oxygen and nutrients and removes waste products)
-Increases enzymatic activity
-Increases metabolic rate
Target temperature window
40 C to 45 C
(104 F to 113 F)
Above 45 C, what will occur
Tissue damage
Below 40 C , what will occur
Mild physiologic response
Heat gain in tissue depends on:
-Body area
-Thickness of subcutaneous fat
-Magnitude of heat dosage
-Treatment duration
Keep this in mind:
Fat has high specific heat capacity, it holds the heat and acts as a barrier and prevents heat from reaching deep tissues, affecting heat gain.
Got it?
Methods of application of superficial heating
Paraffin wax
Hot pack
Hydrotherapy
Fluidotherapy
Infrared
Counterirritants
What is paraffin wax used to treat
Distal parts of the upper and lower extremities
Melting point of wax is
54 C (130 F)
Why is mineral oil used for paraffin wax
To add moisture to the treated area
The paraffin mixture temperature is maintained in a thermoregulated bath with temperatures ranging between …
51 C to 54 C
(124 F -129 F)
First layer of paraffin wax acts as an ______________ to prevent _____________.
Insulator
Heat loss
Recommended application duration of paraffin wax is
30 minutes
Methods of application of wax
Dipping with wrapping
Dipping with continuous Emerson
Brushing with wrapping
Why do hotpacks come in different sizes and shapes
To accommodate different parts of the human body
Hotpacks are heated in a thermoregulated unit called :
Hydrocollators
Temperature in hydrocollators range between
71 C to 74 C
What is important during the application of a hot pack
A coupling medium of layers of toweling is used between the hotpack and the skin surface .
A thick commercial cloth cover may also be used
Why should you never apply hot packs directly over the skin surface ?
Their high heat content can easily burn skin
Recommended duration for hotpack
20 minutes
How many minutes should the hot pack be heated before uses
30 minutes
True or false
Hot pack size should be as large as the tissue area under the treatment
True
General Contraindications of paraffin wax and hot packs
- confused or unreliable patients
- cardiac pacemaker, cardiac insufficiency
- over acute and severe inflammatory pathology
- over thrombophlebitic area
- fever
- over cancerous area
Why is confusion / impaired mentation a general contraindication?
Risk of complications during therapy, reducing treatment effectiveness
Why is acute and severe inflammatory pathology a general contraindication
Risk of worsening the condition by aggravating the inflammatory response through increased blood flow resulting from heat application
Why is a thrombophlebitic Area a general contraindication
Risk of dislodging blood clot, which may then circulate into the vessels of vital organs, causing serious circulatory problems, and possibly death
Why is fever a general contraindication
Risk of adverse reactions 
Why is cancer a general contraindication
Risk of enhancing tumor growth and metastasis
What are LOCAL contraindications
Impaired sensation
Over the abdominal, pelvic, and low back areas of pregnant women
Over hemorrhagic area
Closed and open wounds including grafted or burned wounds
Impaired blood circulation
Metal implants
Why is impaired sensation a local contraindication
Risk of cutaneous burn
Why are the abdominal, pelvic, and low back areas of a pregnant woman a local contraindication
Risk of affect on fetal development and growth caused by increased local and systemic maternal body temperature
Why is a hemorrhagic area a local contraindication
Risk of additional bleeding caused by increased blood flow
Why are wounds a local contraindication
Risk of breaking down immature burn scars and grafts
Why is impaired blood circulation a local contraindication
Risk of tissue overheating
Why are metal implants a local contraindication
May cause internal soft tissue burn due to the high conductivity and specific heat capacity of metals
What are counterirritants
Topically applied ointment that chemically stimulates thermal receptors in the skin which produces sensation of heat or cold
What are counter irritants composed of
Methanol, methylsalicylate, capsaicin
Purpose of counter irritants
Relieve pain from strains and sprains and increase range of motion
How are counterirritants applied
With massaging and vigorous rubbing until no ointment is visible
Revise this
