Heat Flashcards
1
Q
Superficial vs deep heat
A
- Superficial—primarily heat up skin & subcutaneous tissues
- Deep—increase temperature of deeper tissues. Generally reach depth of about 5 cm
- Heating agents transfer heat to the body whereas cooling agents transfer heat away from the body.
2
Q
Thermal Physics – Terminology
A
The First Law of Thermodynamics
- Energy cannot be created or destroyed, only transformed from one form to another
- During transformation heat is released (Thermal Energy)
Heat
- Kinetic Energy = Molecular Motion
- Specific Heat: amount of energy required to raise the temperature a given number of degrees
- different materials used as thermal agents & different body tissues have different specific heats. For example, thermal agents w/a HIGH specific heat (H20) are applied at lower temperatures than air-based thermal agents due to specific heat differences.
Cold
- Decrease in molecular motion = Less Heat
3
Q
Categories of Thermal Modalities
A
A.Heat modalities
- Superficial heat modalities
- Penetrate only 1-3 cm
- Common forms of superficial heat modalities;
- Moist hot packs
- Paraffin bath
- Fluidotherapy
- Warm whirlpool
- Microwavable or air-activated hot packs
- Electric heating pads
-
Deep heat modalities
- Penetrate up to 5 cm deep
- Common forms of deep heat modalities
- Ultrasound
- Diathermy
4
Q
Heat Transfer
- Always transferred from higher to lower temperature molecules
- Until a state of equilibrium is achieved
- MODES of heat Transfer
- Conduction
- Convection-fluidotherapy
- Evaporation
- Radiation
A
Conduction- like hot packs, moist
- Method of heat transfer as a result of energy exchange between 2 materials at different temperatures
- Direct interaction of the molecules in the warmer area with those in the cooler area leading to the speed of molecular movement of both materials becoming equal.
- This process takes time so it is a slow process
Fast moving molecules (warm object) —> Collide —> Slow moving molecules (cooler object)
- Warm object give up energy Slower molecules get energy
- Molecules will move slower Molecules will move faster
Convection
- Heat transfer occurs as a result of DIRECT contact between a circulating medium and another material of a different temperature.
- also same as how body heats up
- During heating or cooling by convection the thermal agent is in MOTION, so new parts of the agent at the initial treatment temperature keep coming into contact with the patient’s body part.
- Examples:
- Fluidotherapy
- Whirlpool
Evaporation
- A material must absorb energy in order to evaporate and thus change form from a liquid to a gas or vapor.
- This energy is absorbed in the form of heat, either from the material itself or from an adjoining material, resulting in a decrease in temperature.
- Example
- sweating
- vapocoolant sprays
Radiation
- Heating by radiation involves the DIRECT transfer of energy from a material with a higher temperature to one with a lower temperature withOUT the need for an intervening medium or contact.
- Radient energy can be propagated through space or matter in all directions. The rate of temperature increase caused by radiation depends of the intensity of the radiation, the relative sizes of the radiation source and the area being treated, the distance of the source from the treatment area, and the angle of the radiation to the tissue.
- All objects (above absolute zero temp) can give off or take on thermal energy through the process of radiation.
- -Example:
- Infrared Heat Lamp
5
Q
Cold vs Heat
A
- Can affect the temperature of tissues to a greater depth than a superficial heat modality
- Temperature gradient between the cold modality and the skin is much larger than heat modalities
- Cooled tissue takes longer to warm up than heated tissue takes to cool down
6
Q
Local vs. Systemic Reactions
A
A.Local reaction
- Localized sweating and swelling with heat
- Localized and pile erection (goose bumps) with cold
- Includes changes in local metabolic rate, blood flow, and skin condition with both heat and cold.
B. Systemic reaction
- Physiological changes occurring in the various systems of the body
- Reactions may include generalized sweating or shivering, or cardiovascular changes such as increased or decreased pulse rate and blood pressure.
7
Q
Dosage
A
1.Mild dosage: 99-101 °F (1-3 degree change within tissue)
- Subtherapeutic
- Warmth
- Moderate dosage: 102 -106 °F (4-7 degree change)
- Beginning to reach therapeutic range
- Hot
- Vigorous dosage: 107 – 113 °F (7- 13 degree change)
- End of therapeutic range
- Above 113 °F, tissue damage can occur
The overall therapeutic range is 104 to 113 °F for using heat modalities
8
Q
Uses of Superficial Heat
A
- Pain Control
- Gating
- Activation of cutaneous thermoreceptors
- Indirect pain control
- Improve healing
- Decrease muscle spasm
- Decrease Ischemia
- Increase Tissue Extensibility
- Increase ROM
- Decrease Joint stiffness
- Max benefit when heat plus stretch (104-113F maintained for 5-10 min
- Low load prolonged stretch – while heating or immediately after
- Accelerates Healing
- Increase circulation
- Increase enzymatic activity
Increase blood to tissue
Increase oxygen, nutrients
Decrease waste products
Beneficial during the proliferative or remodeling stage
Acute vs Chronic inflammation
- Heat not typically used during acute inflammation
9
Q
Physiological Responses to a Rise in Tissue
Temperature
A
Physiological Responses to a Rise in Tissue Temperature
- There is a decrease in blood viscosity.
- a. Blood becomes thinner
- b. There is less resistance to flow so BP drops.
- c. There is an increase in local sweating.
- With an increase in heat there is a corresponding increase in metabolism. (must be able to get rid of waste or pH will get too low)
- Increase in enzymatic/metabolic activity: 102-109 degrees F
- continue to increase up to 113 degrees F
- protein denatures and enzymatic activity ceases 122 degrees F
Van’t Hoff’s Law (or van’t Hoff’s effect)
If tissue temperature rises 10 degrees, there is a two- or three-fold increase in metabolism.
10
Q
Clinical Application of Heat Modalities
A
- In the presence of muscle spasm to relax the patient.
- Used prior to active exercise because of the analgesic and sedative effects.
- Before traction to promote relaxation and to reduce muscle tension.
- Before massage to increase local blood flow and to relax the tissue.
- Before stretching and joint mobilization techniques because the heat will relax the patient and improve the extensibility of superficial soft tissue. Paraffin treatment is especially effective when used before joint mobilization of the hands and feet because it can raise the temperature in small joint capsules of the hand 13.5° F (7.5°C) at a depth of about 0.5 cm below the skin.
- Before electrical stimulation to reduce skin impedance. (warmer skin = lower impedance)
11
Q
Contraindications of Heat Modalities
A
- Acute inflammatory conditions may be aggravated by the addition of heat
- Already existing fever may be elevated further by heating the patient.
- Malignancies may metastasize due to the increased blood flow produced by heating.
- Active bleeding, such as that which occurs with acute trauma, may be prolonged.
- Patients with cardiac insufficiency/PVD may not be able to tolerate the additional stress on the heart, which is produced by generalized heat.
- Extremely old adults and children less than 4 years old have unreliable thermoregulatory systems and may develop a fever quite easily as a result of generalized heat treatments.
- Patients with peripheral vascular disease have a diminished capacity to meet the increased metabolic demands of heated tissues.
- Tissues which are devitalized by x-ray therapy should not be heated.
- Recent or potential hemorrhage (acute trauma)
- Thrombophlebitis
- PVD (peripheral vascular disease): diminished capacity to meet the increased metabolic demands of heated tissues.
- Impaired sensation
- Impaired cognition
- Malignant tumors (may metastasize due to increase blood flow)
- X-ray therapy patients (tissues are devitalized)
12
Q
Heat precautions
A
- Acute Inflammation
- Pregnancy
- Impaired Circulation
- Poor thermal regulation (geriatrics, kids under 4 y.o.)
- Edema
- Cardiac Insufficiency
- Metal in area
- Over an open wound
- Over an area where topical counterirratants have been applied recently
- Demylinated nerves
13
Q
Commercial Hot Packs
A
- .The commercial hot pack is a conductive means of delivering moist heat to the patient.
- The pack is made of canvas or nylon and is filled with silica gel.
- The pack is immersed in water of about 158-167° F (70 – 75 °C) in a thermostatically-controlled heater.
- The pack is capable of retaining heat for about 1/2 hour.
- Provide superficial heat
- Advantages vs. Disadvantages
14
Q
Advantages/ disadvantages Hot Pack
A
Advantages:
- ease of prep and application
- variety of shapes
- moist, comfy
- inexpensive
Disadv:
- No method of temp control
- do not conform to all body parts
- sometimes awkward in place
- do not retain heat for longer than 20 min
- passive intervention, no pt involvment
- may leak
15
Q
Advantages and Disadvantages of Paraffin Wax
A
Advantages and Disadvantages of Paraffin Wax
Advantages:
- Low specific heat = higher temperature
- Low thermal conductivity = slower heating and decrease risk of burns
- Even distribution
- Oils moisten skin
- Wax can be used for exercise
Disadvantages:
- Effective for only distal extremities
- No method for temperature control
- Heating only lasts 20 minutes
