Heat & Cold Physics Flashcards
5 things physical therapists and patients should question
- Don’t use (superficial or deep) heat to obtain clinically important long term outcomes in musculoskeletal conditions
- Don’t prescribe under-dosed strength training programs for older adults. Instead, match the frequency, intensity and duration of exercise to the individual’s abilities and goals
- Don’t recommend bed rest following diagnosis of acute deep vein thrombosis (DVT) after the initiation of anti-coagulation therapy unless significant medical concerns are present
- Don’t use continuous passive motion machines for the postoperative management of patients following uncomplicated total knee replacement
- Don’t use whirlpools for wound management
Types of Spectra
spectra = bands of energy
- electromagnetic spectrum
- acoustic spectrum
Electromagnetic Spectrum
emit energy with wavelengths & frequencies; electromagnetic radiation, radiant energy and diathermies
Acoustic Spectrum
Subset of radiant energy, but sound vs. electromagnetic
Acoustic energy travels at ____ velocities
lower
Acoustic energy is more effectively transmitted through ____ tissue vs. electromagentic energy
dense
Acoustic energy is ____ penetration vs. electromagnetic energy
deeper
Radiant energy
process by which energy in various forms travels through space; ROYGBIV
Radiant energy is at a _____ temperature and thus a _____ activity
higher; greater
What are the regions of the electromagnetic spectrum?
- Visible Spectrum
- Invisible Spectrum
a. Infrared
b. Ultraviolet
Infrared is located beyond the visible ____ and produces ____, which means it penetrates the skin ___
red; heat; 1cm
Ultraviolet is located beyond the visible ____ and produces ____ changes, which means it is very _____ and only penetrates 1-2mm.
violet; chemicals; superficial
Electromagnetic Radiations are produced when sufficiently intense ____ or ____ forces are applied to any material
electrical; chemical
Radiant energy may be _____, _____, _____ or _____ depending upon the medium they strike (especially in tissues)
reflected, refracted, absorbed, transmitted
Wavelength
Distance b/w peak of one wave and peak of preceding or succeeding wave
Frequency
Number of wave oscillations occurring in 1 sec (hz)
Velocity is equal to
Wavelength x Frequency
Longer wavelengths produce
lower frequencies
Shorter wavelengths produce
higher frequencies
Radiant Modalities
purpose is to stimulate a specific body tissue to perform its normal function
What are the various Radiant Modalities?
DULUI(th)
- Diathermies (microwave/shortwave)
- Infrared (cold packs, whirlpool, paraffin, moist heat)
- Ultraviolet
- Laser
- Ultrasound
Effects of Media (in what 4 ways can energy travel?)
- Reflection
- Absorption
- Refraction
- Penetration
Which media produces the longest wavelengths, greatest depth regardless of frequency?
Penetration
Reflection strikes the surface of skin and _______. It produces _____ physiological response and the ___ reflected depends upon frequency
bounces off; NO; %
The 2 Absorption Principles/Laws
- Arndt-Schultz Principle
2. Law of Grotthuss-Draper
What does the Arndt-Schultz Principle state?
No reactions or changes can occur in the body tissues if the amt of energy absorbed is insufficient to stimulate the absorbing tissues
What does the Law of Grotthuss-Draper state?
Energy that is NOT absorbed will penetrate to deeper tissue layer
Refraction occurs at
tissue interfaces
Penetration has no
reflection, refraction or absorption
What are 3 additional laws related to heat & cold physics besides Draper and Arndt?
- Cosine Law
- Inverse Square Law
- Bunsen Roscoe Law of Reciprocity
What does the cosine law state? What modalities is it delivered through?
- The smaller the angle b/w the energy source and 90 dg, the less reflected. This is why the sun is most intense at noon because it’s almost perpendicular
- The air; diathermies, UV, infrared heat
What does the inverse square law state?
hint: intensity varies inversely with the ____ of the distance from what?
Intensity varies INVERSELY with the square of the distance from the source
Diathermy, radiation & UV
I = 1/D^2
What does the Bunsen Roscoe Law of reciprocity state?
Intensity and duration of the dose of radiant energy are INVERSELY proportional; the pizza example
Energy = Intensity x Time
What are the categories of thermal modalities?
- Heat (thermotherapy)
a. superficial
b. deep - Cold (cryotherapy)
Local Application
requires a specific modality; specific area of treatment such as ultrasound or ice cup massage
General Application
Larger, non-specific treatment such as whirlpool, hot pack, ice pack. Helpful for dx of non-specific LBP
Local Reaction
physiological changes ocurring at the site of local application
Systemic Reaction
physiologic changes occurring in the various systems of the body such as an increase in the circulatory system
Specific Dosage
Precise treatment factors based on INJURY and TARGET TISSUES, such as E-stim
General Dosage
the effect the modality has on the patient (hotpacks, coldpacks); can’t really set parameters but CAN change temperature
The 4 dosage reactions of tissues
MMVC
- Mild
- Moderate
- Vigorous
- Critical Cooling
Mild change in tissue temp provides what?
sensation benefit
Moderate change in tissue temp
TT increased to 100-105F; slight increase in blood flow
Vigorous change in tissue temp
TT increased to 106-113F (max) significant heating with marked increase in blood flow (RISK OF BURNS!)
Critical Cooling change in tissue temp
TT drops to 32-50 degrees
50 degrees F has the greatest amount of ______ and 32 degrees F has the greatest amount of _____
vasoconstriction; vasodilation
Changes in firing of thermal sensory neurons depend on (3)
- type of receptors
- type of stimulus (heat, cold, pain)
- surface area
Considerations of specific dosages
- Parameters of treatment (intensity, duration, frequency - how often)
- Specific absorption rate of tissues
Thermal energy =
kinetic energy
Heat =
molecular motion in matter
1st law of thermodynamics states that energy cannot what?
energy CANNOT be lost, but can be transformed from one form to another
4 methods of heat transfer (RCCC)
- Radiation
- Conduction
- Convection
- Conversion
Radiation is energy transmitted from _____ to ______ source through a conducting medium
WARMER to COOLER
Conduction is
heat transfer through DIRECT CONTACT with a cold or heat source
Convection is
particles of air or water moving across tissue to create a TEMPERATURE GRADIENT
Conversion is
changing from ONE energy form into ANOTHER
What is an example of radiation?
ultraviolet light from the sun
What is an example of conduction?
A non-moving hot tub/whirlpool
What is an example of convection?
A moving hot tub/whirlpool, sprinklers during a marathon to help cool down runners
What is an example of conversion?
ultrasound, diathermy
Density is the ___ of a substance per unit ____
mass; volume
Thermal expansion is the change in _____ of a substance related to _____
density; temperature
Quantity (Q) of heat =
the amt of energy required to increase/decrease molecular motion enough to change temperature
Q = ___ x ____ x ____
S x Mass x Temp; expressed in calories; s is specific heat capacity of a substance
Specific Heat Capacity (S) is
the specific heat input required to raise the temp of 1 gram of a substance 1 degree celsius
S is influenced by (2)
- Starting temp of substance
2. Type of fluid intermolecular bonds
S for water
1 cal/g x Cdeg
S for paraffin wax
0.65 cal/g x Cdeg
At any given temperature, paraffin contains ___ heat than water
less
Thermal conductivity is
the ability of a particular substance to conduct heat
Conductors permit the free movement of
heat
Insulators restrict the free movement of
heat
Homeotherm is
the constant core temp largely independent of the surroundings
Core temperature
98.6 F
Shell
decreases as move distally; subcutaneous 1-2F higher than skin
Heat Loss (5)
- Conduction (core to shell)
- Convection (blood flow)
- Radiation (warm body to cooler environment)
- Evaporation (sweat & respiration)
- Ambient Air Flow (conduction/convection due to wind flow)
Heat Gain rise of tissue temps depends on (3)
- Ability of modality to GIVE heat to body
- Physical properties of tissues
- Integrity and response of body systems