Thermal Agents

You evaluate a patient 2-days after a cast is removed from their left ankle. They fractured their L lateral malleolus 8 weeks ago and the fracture is now healed. You find limited ROM, strength, and increased edema on the left as compared to the right. You position the patient in supine, with their foot and ankle elevated above the heart and instruct them to perform ankle pumps. Which of the following would be the most appropriate thermal agent to add to this exercise to help meet your goals? a. A crushed ice bag secured to the ankle with an ace wrap bandage b. A moist hot pack, secured to the ankle with an ace wrap bandage

*A moist hot pack, secured to the ankle with an ace wrap bandage* Rationale: This patient is 8-weeks s/p fracture and is no longer in the acute inflammatory phase and therefore, does not need cryotherapy to help control any acute edema. The edema that is present is due to decreased venous circulation due to immobilization. Improving movement will help to improve the muscle pump, improve circulation, and reduce edema. Heat will help increase blood flow to the area and reduce muscle/joint stiffness which can promote more movement and help pump the static edema out of the area. Cryotherapy would reduce blood flow and could cause more joint/muscle stiffness, making it harder to pump the static edema out of the area.

You decide to start using a moist hot pack (MHP) with a patient who is 2 weeks s/p right knee meniscectomy. You would like to test the patient's quadriceps and hamstring strength to compare to the values that you found at the initial evaluation. Which of the following would be the best time to perform this test? a. At the start of treatment session b. Immediately after a 30-minute MHP treatment to right knee c. 30 minutes after MHP treatment and immediately after riding a stationary bike for 15 minutes d.. 15 minutes after a 30-minute MHP treatment to right knee

*At the start of treatment session* Rationale: Testing the strength before starting the treatment session will give you the most comparable test to the initial evaluation. Muscle strength and endurance has been found to decrease during the initial 30 minutes after the application of deep or superficial heating agents. Therefore, testing strength within this 30-minute window would likely result in a decrease in strength compared to their "true strength". If you also test the patient after riding a bike for 15 minutes, he will likely be even more fatigued and this not allow you to compare strength from today's session to the initial evaluation. Muscle strength and endurance gradually recovers and then increases to above pretreatment levels over the next 2 hours.

Your patient needs soft tissue stretching to the right wrist, and you decide to use thermotherapy prior to stretching. Which of the following needs to be at a higher temperature to transfer the same amount of heat to the patient? a. Fluidotherapy b. Moist Hot Pack (MHP)

*Fluidotherapy* Rationale: Water has a higher specific heat (4.19 J/g/C°) compared to air (1.01 J/g/C°). The temperature of the water for the moist hot pack treatment is usually between to be 99-104°. The temperature of air for fluidotherapy treatment is usually between 100-118°

Metal jewelry must be removed from any area being treated with a thermal agent because it has a (higher/lower) level of thermal conductivity than the body.

*Higher* Rationale: Metal has a higher level of thermal conductivity, meaning that it will heat up much faster than the surrounding skin, increasing the risk of burn. Metal also has a lower specific heat as compared to skin which means that it will heat up faster than the skin, also increasing the risk of burning the patient.

Which would be the most appropriate use of thermotherapy? a. Moist hot pack to the posterior knee in a patient with global aphasia following a stroke, to reduce muscle tone and promote knee extension. b. Moist hot pack to the cervical spine of a pregnant female to reduce pain and promote muscle relaxation prior to exercise and manual therapy. c. Moist hot pack to the hamstrings 4-days s/p a grade III hamstring strain resulting in significant localized bruising, to improve flexibility prior to stretching exercises. d. Moist hot pack to the anterior knee following a total knee replacement when staples are still intact, to reduce pain and improve knee joint range of motion.

*Moist hot pack to the cervical spine of a pregnant female to reduce pain and promote muscle relaxation prior to exercise and manual therapy.* Rationale: Pregnancy is listed as a precaution for thermotherapy if it results in full body heating, such as submersion in a whirlpool. It is also generally recommended not to apply hot packs to the low back or abdomen out of caution, although superficial heat is unable to penetrate to the level of the fetus. The use of a moist hot pack to the cervical spine would be safe during pregnancy. The use of a MHP over a recent acute injury with bruising would be contraindicated as it would be over an area of recent hemorrhage and could increase or restart bleeding in the area. MHP would also be contraindicated for a patient with global aphasia as they have impaired mentation and are unable to fully understand your instructions, or communicate if they are having discomfort. A stroke patient may also have impaired sensation on their involved side. The use heat over metal, such as staples following a total knee replacement, is also a precaution and while you could increase padding and monitor closely, it would not be recommended and would be a less appropriate use as compared to the use of a moist hot pack to the cervical spine during pregnancy.

Thermotherapy: Hemodynamic Effects

*Vasodilation* - Direct reflex activation of smooth muscles of blood vessels by cutaneous thermoreceptors - Indirect activation of local spinal cord reflexes by cutaneous thermoreceptors - Decreased sympathetic activity results in vasodilation at site and in distal extremities - Local release of chemical mediators of inflammation

Thermotherapy: Altered Tissue Extensibility

*When soft tissue is heated before stretching*: - Maintains a greater increase in length - Less force to achieve increase in length - Decreases risk of tissue tearing *Maximal increase in residual length is achieved when target tissue temperature is maintained between 104°-113° F x 5-10 min.* - Superficial heating agents (such as MHP) can cause this level of increase in superficial structures only (cutaneous scar tissue or superficial tendons) - MHP unable to adequately heat deeper structures (joint capsules of large joints or deep tendons) - Deep heating agents or Exercise are much more effective at warming deeper structures. - Exercise has additional benefits and is more functional

Thermotherapy: Precautions

- *Acute injury/inflammation*: Vasodilation leads to increase in edema - *Pregnancy*: Avoid full body heating - *Impaired circulation*: Sufficient blood flow to prevent burning; Inspect area. - *Edema*: Increases edema, especially in dependent position - *Cardiac insufficiency*: May increase cardiac demand - *Metal in area*: Lower specific heat and higher thermal conductivity --> may become very hot - *Open wounds*: Cross contamination, more insulation - *Recent topical counterirritant*: Vessels already dilated (cannot dilate any more) - *Demyelinated nerves*

Adverse Effects of Thermotherapy

- *Burns*: #2 cause of malpractice suits - *Fainting*: Most commonly caused by peripheral vasodilation and decreased BP in association with decreased HR - *Bleeding*: May aggravate bleeding in areas of acute trauma or hemophilia; Re-open recent lesion - *Skin/eye damage from IR*

Thermotherapy Effects of Heat

- *Hemodynamic effects*: Vasodilation - *Neuromuscular effects*: Changes in nerve conduction velocity and firing rate. Increased pain threshold. Changes in muscle strength. - *Increased metabolic rate* - *Increased tissue extensibility*

Thermotherapy: Contraindications

- *Recent or potential hemorrhage*: Vasodilation leads to increase rate of blood flow (bruise, hematoma) - *Thrombophlebitis*: Vasodilation and increased blood flow may cause clot to dislodge - *Impaired sensation* - *Impaired mentation* - *Malignancy*: May increase growth rate over tumor site (increased blood supply) - *IR irradiation of eyes*: Wear IR goggles during IR lamp treatment

Cryotherapy Precautions

- *Superficial main branch of nerve* (even healthy nerves): Changes in nerve conduction - *Open wound*: May delay healing. Areas with superficial wounds are less responsive to cooling agents. - *Hypertension*: Transient increases in systolic or diastolic pressure - *Poor sensation*: Closer monitoring - *Poor mentation*: Closer monitoring - *Very young/very old*: Impaired thermal regulation

Cryoglobulinemia

- Aggregation of plasma proteins that causes local ischemia and gangrene. - Idiopathic or may be associated with multiple myeloma, lupus, RA.

Documentation must include:

- Area of treatment - Type of agent - Duration - Patient position - Response to intervention

Documentation includes:

- Area treated - Heating agent - Treatment parameters: Temperature/power; Insulation/distance - Patient positioning - Response to intervention

Claims against PTs

- Causes are errors in "simple" rehab techniques: heat modalities and therapeutic exercise - Burns: inappropriate use or improper application of HPs - Many claims involve patients with sensory loss: diabetes, spinal cord injury

Cryotherapy Contraindications

- Cold hypersensitivity - Cold intolerance - Cryoglobulinemia - Paroxysmal cold hemoglobinuria - Raynaud's disease/phenomenon - Area of regenerating peripheral nerves - Area of circulatory compromise

Cryotherapy: Metabolic effects

- Decreased metabolic rate - Control *acute* inflammation (not recommended if healing is delayed for some reason; not for chronic inflammation)

Thermotherapy: Increased Pain Threshold

- Direct: Spinal gating mechanism (distraction) - Indirect: reduction of ischemia and muscle spasm; facilitation of tissue healing (more blood flow)

Thermotherapy: General Contraindications in Patients with Cancer

- Directly over tumor site - In radiation field during time period of radiation therapy and for a few months after - Risk of toxicity: enhancement of treatment effects leading to radiation burn - Increased blood flow may enhance treatment effects - Implants, tissue expanders that are in application area - Insensate area and over injured area (dysvascular, fibrosed skin and capillary beds).

Uses of Cryotherapy

- Inflammation control - Edema control - Pain control - Reduction in Muscle Guarding - Modification of spasticity—prolonged icing - Symptom management in MS—cooling vest - Facilitation - Cryokinetics and cryostretch

Thermotherapy: Changes in Muscle Strength

- Initial 30 min: decreased strength - Gradually recovers and then increases to above pretreatment levels over next 2 hours --> Possibility due to increased pain threshold

Thermotherapy: Increased nerve conduction velocity and decreased conduction latency of motor and sensory nerves

- May reduce muscle spasm - Use heat with caution in demyelinating conditions (e.g. CTS, MS) --> May cause conduction block

Thermal Agents & Patients with Cancer

- Most common symptom is pain - Peripheral neuropathies: Chemotherapy - Sensory impairments: Radiation therapy, chemotherapy, surgery, comorbidities (DM), electrolytes

Cryotherapy: Hemodynamic effects

- Vasoconstriction of superficial vessels - Depth to 1-4 cm (0.4 -1.5 inch) - Affected by adipose tissue (insulator) Cold-induced vasodilation - Response to extended exposure to cold - "Hunting Response": Cyclical increase and decrease in tissue temperature. - Occurs when cold applied for >15 min, or when tissue temp reaches <50° F (10°C). - Reported by Lewis in 1930. - Primarily in fingers and toes.

Specific heat (J/g/C) of various materials

- Water: 4.19 - Skin: 3.77 - Muscle: 3.75 - Average for human body: 3.56 - Fat: 2.30 - Bone: 1.59 - Air: 1.01 - Sand: 0.83 - Metal: < 1.0 Eg. when you get into car on hot day, air is very hot but it will not burn you. If you touch metal, it could burn you.

Screening Questions

- When did injury occur? - Did you have any bruising or bleeding? - Do you have any sensitivities to heat? - History of blood clots? Any redness, swelling, tenderness in area? - Do you have normal sensation in this area? - Are you pregnant? - Do you have poor circulation in this limb? Assess skin temp and color - Do you have any cardiac conditions?

Thermotherapy: Neuromuscular Effects

1) Increased nerve conduction velocity and decreased conduction latency of motor and sensory nerves 2) Increased Pain Threshold 3) Changes in Muscle Strength

Cryotherapy: Neuromuscular effects

1. *Decreased nerve conduction velocity* - inhibits pain transmitting fibers, A-delta (cold can help with pain by slowing pain signals) 2. *Increased pain threshold* - gate-control theory; decrease in muscle spasm; decreased sensory NCV; decreased edema 3. *Decreased spasticity* - decrease in gamma motor neuron, spindle, and golgi tendon organ (GTO) activity after 30 minutes of icing (if goal is to reduce spasticity, need to do prolonged icing/need longer cooling time). 4. *Facilitation of muscle contraction* - <5 min: isometric strength increases - >30 min: initial decrease in isometric strength; then increase in strength an hour later (Important: Test strength BEFORE icing)

General Superficial Thermotherapy Application Technique

1. Evaluate patient and set goals 2. Determine if thermotherapy is most appropriate intervention 3. Contraindications/Precautions?: Inspect treatment area; Review chart; Ask screening questions 4. Select appropriate heating agent: Location/site, desired position, etc 5. Explain procedure, reasoning, and expected sensations to patient 6. Apply appropriate superficial heating agent 7. Inspect treated area and assess outcome of treatment 8. Document intervention

Cryotherapy Application Technique

1. Evaluate patient and set goals of treatment. 2. Is cryotherapy appropriate? 3. Any contraindications or precautions? 4. Select most appropriate cooling agent. 5. Explain procedure and expected sensations. - Intense Cold --> Burning --> Aching --> Analgesia --> Numbness (C-BAAN) 6. Apply appropriate agent. 7. Assess outcome. 8. Document intervention.

Cryotherapy: Effects of Cold

1. Hemodynamic 2. Neuromuscular 3. Metabolic

Uses of Superficial Heat

1. Pain control 2. Increased ROM and decreased joint stiffness 3. Accelerated healing 4. Infrared radiation for psoriasis/dermal ulcers

Thermotherapy: Maximal increase in residual length is achieved when target tissue temperature is maintained between ___________ for ____________.

104°-113° F 5-10 min

Specific heat

Amount of energy required to raise the temperature of a given weight of a material by a given number of degrees - Higher the specific heat - More energy required to increase temperature - Holds more energy at a given temperature Eg. On beach it is hotter to walk on dry sand than in water. Water has higher specific heat than sand - it takes more energy to heat water up to same temperature. If water could get to same temperature as sand, it would stay warm longer; will not fluctuate as much.

Vasodilation occurs when using thermal agents in an attempt to bring that area of body back to normal temperature. This is an example of: a. Radiation b. Conduction c. Evaporation d. Conversion e. Convection

Convection

Conversion

Converts nonthermal form of energy into heat. - Mechanical, electrical, or chemical energy: Ultrasound causes mechanical vibration of molecules. Diathermy applies electromagnetic energy to body (to create heat). Is unlike heating by conduction or convection: - Temperature of thermal agent is not important --> Rate of heat transfer depends on power of energy source, NOT temperature of thermal agent. - Does not require direct contact but requires *intervening material* - May have other electrical or mechanical effects besides heat on body (pulsed/lower power = not warming up but other physiological effects)

Which is a proposed mechanism for increased pain threshold experienced following cryotherapy? a. Increased muscle spasm b. Increased sensory nerve conduction velocity c. Counter-irritation via the gate control mechanism c. Increased edema

Counter-irritation via the gate control mechanism

Area of regenerating peripheral nerves

Delays regeneration

Radiation

Direct transfer of energy without need for intervening medium or contact. - Rate of temperature change depends on: 1. Intensity of radiation 2. Relative sizes of radiation source and treatment area 3. Distance and angle of radiation to treatment area Eg. fire, infrared

Cryotherapy Screening Questions

Do you have any unusual responses to cold? - If YES: - Do you develop a rash? - Experience severe pain, numbness, and color in fingers? - Notice blood in urine? Do you have nerve damage in this area? - Numbness/Tingling in area? - Test sensation Do you have poor circulation in this limb? - Assess skin temp and color

Area of circulatory compromise

Edema is cool and pale

Conduction

Energy exchange by direct collision between molecules of two materials at different temperatures. - High to low - Requires *direct* contact of targeted area with heating or cooling agent - Hot pack or warm paraffin; ice pack Safe and effective rate of heat transfer requires: - Choosing materials with moderate thermal conductivity - Ensuring tolerable differences in temperature - Using insulators to limit rate of heat transfer

Evaporation

Energy is absorbed to change liquid into gas or vapor. - Material that contributes energy for evaporating liquid is cooled in process. - Examples: As vapocoolant spray or sweat evaporates, it cools skin that heated it and turned it into vapor. - Humidity impairs evaporation

Convection

Heat transfer by direct contact between *circulating* medium with another material of different temperature. - Transfers more heat than conduction - Eg. whirlpool and fluidotherapy; circulating blood helps maintain physiologic temperatures by convection; cools faster via whirlpool vs. stagnant bucket of ice

Paroxysmal cold hemoglobinuria

Hemoglobin released from RBCs to urine

Thermotherapy: Metabolic Effects

Increased rate of cellular biochemical reactions - Accelerates healing in chronic injuries - May also increase rate of destructive processes: Acute inflammatory disorder (RA - avoid heat directly over joints); May accelerate destruction of articular cartilage

You apply a cold gel-pack to a patient's knee with a damp towel for 20 minutes and achieve good results. You then educate the patient to perform this at home with a bag of ice and a damp towel but educate them that it may take ________ time to cool the tissues at home, because of the difference in specific heat between a gel-pack and an ice-pack. a. More b. Less

Less

Cold intolerance

Severe pain, numbness, and color changes

Principles and modes of heat transfer

Specific heat, conduction, convection, conversion, radiation, evaporation

Raynaud's disease/phenomenon

Sudden palor and cyanosis followed by redness in response to cold or emotional upset. Relieved by warmth.

Adverse Effects of Cryotherapy

Tissue death or damage - Damaged <59° F - Freezing/frostbite 39° to 50° F or lower - Always keep tissue temperature >59° F

Cold hypersensitivity

Transient appearance of smooth, slightly elevated patches, which as redder or more pale than the surrounding skin; often itchy

Which are effects of heat? a. Vasodilation, decreased collagen extensibility, decreased pain b. Vasodilation, increased collagen extensibility, decreased pain c. Vasoconstriction, increased collagen extensibility, decreased pain d. Vasodilation, decreased collagen extensibility, increased pain

Vasodilation, increased collagen extensibility, decreased pain

Match thermal agent with mode of heat transfer that best describes mechanism behind that specific thermal agent. a. Hot Pack b. Whirlpool c. Ultrasound d. Infrared lamps e. Vapocoolant spray

a. Hot Pack - Conduction b. Whirlpool - Convection c. Ultrasound - Conversion d. Infrared lamps - Radiation e. Vapocoolant spray - Evaporation