Thermal Therapy Quiz

Therapeutic Heat Modalities - Lecture Objectives

• Understand the biophysical effects of temperature elevation
• Understand the basic physical principles of thermotherapy
• Recognize indications, contraindications, and precautions for heat therapy
• Effectively assess outcomes following treatment

Clinical Scenario

• Patient: 55-year-old male with gradual onset shoulder stiffness, limited range of motion on elevation, over a 6-month period.
• Goal: Stretch the shoulder.
• Question: Would hot or cold be chosen? Why?
• Question: What specific modality would be used, and why?

Thermotherapy Modalities

• Heat superficial joints to cause a heating effect in deeper structures.
• Heat causes soft tissue to become more extensible.

Thermal Modality Options

• Increase temperature 1-3 cm:
  • Moist heat packs
  • Paraffin wax
  • Fluidotherapy
  • Warm whirlpool
  • Microwavable gel packs
  • Air-activated heat wraps
  • Electric heating pads
• Increase temperature 1-5 cm:
  • Continuous ultrasound
  • Shortwave diathermy

Heating

• Heating is the nonmechanical transfer of energy related to a temperature difference between a system and its surroundings.
• Heat always moves from the warmer to the cooler object.

Heat vs. Temperature

• Heat is energy, while temperature measures heat.
• Heat energy depends on particle speed (kinetic energy), number of particles (mass), and capacity to store heat (specific heat).

Properties

• A table of properties of various substances, including specific heat and thermal conductivity. Values are provided for various substances.

Heating - Modes for Energy Transfer

• Conduction
  • Moist heat packs
  • Paraffin wax
  • Electrical heating pads
  • Air-activated heat wraps
• Convection
  • Fluidotherapy
• Radiation
  • Infrared

Conduction

• Conduction is the transfer of heat by direct interaction of molecules.
• The formula for heat transfer by conduction is provided: D = (Area) x k x (T₁ - T₂)/(thickness of tissue).
• Factors affecting heat gain include thermal conductivity of tissues, body volume exposed, and time of exposure.
• Local effects include blood flow, vasodilation, and tissue temperature.

Convection

• Convection is heat transfer related to bulk movement of molecules (liquid or gas).
• Examples include warm whirlpool treatments, and fluidotherapy.

Radiation

• Radiation is the direct transfer of energy from a higher-temperature substance to a lower-temperature substance without direct contact. It commonly travels via waves.
• Infrared lamps are an example of this method of heat transfer.

Biophysical Effects of Temperature Elevation

• Factors that determine the effects of heat include tissue temperature rise rate, rate of energy transfer, volume of tissue, tissue composition, and blood supply to dissipate heat.
• Therapeutic level: 40°C to 45°C (104°F to 113°F). Higher temperatures (above 113°F) can damage tissues. Lower temperatures (below 104°F) produce only mild heat effects.

Biophysical Effects of Temperature Elevation - Metabolic Changes

• Increased skin & tissue temperature increases metabolic rate (and cell activity) by 2-3 times for every 10°C increase.
• Increases oxygen uptake by tissues.

Biophysical Effects of Temperature Elevation - Connections Among Tissues

• Connective tissues, vascular systems, neuromuscular systems, and skeletal musculature all interact.

Biophysical Effects of Temperature Elevation - Skin

• Skin blood flow and vasodilation in response to heat are sympathetic adrenergic reactions regulated by arteriovenous anastomoses.
• The hypothalamus contains temperature receptors for regulating blood flow.

Axon Release

• Heat (stimuli) interacts with cutaneous thermoreceptors.
• Signals in turn stimulate the release of vasoactive mediators, leading to vasodilation.

Release of Chemical Mediators

• Chemical mediators like prostaglandins, histamine, and kallikrein contribute to vasodilation.
• Bradykinin increases vascular permeability.

Local Spinal Cord Reflex

• Heat activates spinal cord afferents in skin.
• Activation decreased post-ganglionic sympathetic adrenergic activity to smooth muscle of blood vessels.
• Generally not clinically indicated.

Biophysical Effects of Temperature Elevation - Skeletal Muscle

• Metabolic regulation (like movement or exercise) affects heat impacts on skeletal muscle.
• Moderate evidence suggests an additive effect in movement with heat, in contrast to passive heating.

Biophysical Effects of Temperature Elevation - Neuromuscular Effects

• Temperature influences pain (and muscle spasm), nerve conduction speed, and pain thresholds.
• Increased temperature can alter firing rate in muscle, associated with tonic muscle fiber activity. Thermotherapy devices might not always increase muscle temperatures significantly enough.

Biophysical Effects of Temperature Elevation - Connective Tissue

• Increased tissue temperatures can enhance flexibility and elasticity, decreasing viscosity and stiffness. This is frequently applied with stretching.

Biophysical Effects of Temperature Elevation - Plastic vs. Elastic Elongation

• Elastic elongation returns to original length when stress is removed.
• Plastic elongation is a residual elongation after stress. Connective tissue demonstrates this.

Biophysical Effects of Temperature Elevation - Concept of Heat

• Partial melting of collagen bonds increases connective tissue pliancy. The critical temperature for collagen deformation is ~ 39 °C.

Biophysical Effects of Temperature Elevation - Strategies to Overcome Elasticity

• Techniques include constant stretching, high-magnitude stretching, followed by hold, and maintaining a constant stretching rate.

Conductive Heat Modalities - Quantity and Physiological Response

• Heat gain and response are contingent on tissue conductivity, intensity, volume, and exposure time.
• Most changes are evident in skin and subcutaneous tissue within 6 −8 minutes, and deeper tissue takes longer.

Conductive Heat Modalities - Adipose Tissue

• Adipose (fatty) tissue is a good insulator, and thermal conductivity is low in adipose tissue.
• Deep heating is preferred over superficial heating when significant temperature increases are needed in tissues beneath an adipose layer. Risk of burning is greater when more adipose tissue is present.

Conductive Heat Modalities - Moist Heat Packs

• Hydrocollator packs are commonly used and provide comfortable heat. Temperatures are between 158−165 °F. Multiple layers and avoidance of direct contact can be important considerations in the use of these packs.
• Advantages include ease of preparation and application, moist heat comfort, and low cost.
• Disadvantages include lack of temperature control, conformance difficulty, and limited heat retention (typically for under 20 minutes).

Conductive Heat Modalities - Paraffin Wax

• Paraffin wax provides even heat distribution.
• It has a low specific heat; thus risk of burns is lower than with other methods that heat up rapidly.
• The primary application forms include dip and wrap (8−10 dips, followed by 15−30 minutes of wrap treatment) and dip and reimmerse (10−20 minutes of dip and reimmersion).
• Wax is applied frequently in the treatment of peripheral extremities (e.g. hands).

Conductive Heat Modalities - Electric Heating Pads

• Electric heating pads are often used at home.
• Advantages include convenient use, low cost, and comfort.
• Disadvantages include the risk of burns and the need for an external power source.

Conductive Heat Modalities - Air-Activated Wearable Heat Wraps

• Providing heat using air-activated wearable wraps is possible.
• These wraps have temperatures around 104 °F.
• Advantages include delivering dry heat, comfort, safety during movement and stretching, and cost.
• Disadvantages include the fact that they are only intended for use once before being re-filled. These are primarily utilized for short-term applications.
• Other disadvantages include cost when used over an extended period and the need to be used on just one part of the body.

Convective Heating Modalities - Fluidotherapy

• This convective method uses fluidized solids.
• Temperatures are generally between 102−118 °F.
• Advantages include easy to administer and control of temperature (useful for sensitive areas like hands or feet).
• Disadvantages include that they are expensive, and some patients are sensitive to the dry material used (and/or the enclosed container).

Contrast Baths

• Hot and cold water alternating immersion provides heating, followed by cooling cycles.
• Typical hot water temperatures are 100−110 °F and cold 55−65°F.
• Treatments usually include 3−4 minutes in hot water, followed by 1−2 minutes in cold water. The ratio can vary according to specific treatments and patient needs.

Clinical Application, Principles, and Indications (Heating)

• Heat is used to diminish pain, stiffness, and muscle spasms.
• Heat increases range of motion and blood flow, which promotes tissue healing.
• Application times generally range from 15 to 30 minutes.

Contraindications to Thermotherapy

• Large areas, or high intensities that raise a patient’s internal temperature (pregnant women)
• Regions of known or suspected malignancy
• Tissues with infection or tuberculosis
• Tissues that are inflamed due to recent injury or exacerbation of chronic inflammation
• Persons with active DVT or thrombophlebitis
• Areas with impaired sensation
• Areas of recent hemorrhage

Contraindications to Thermotherapy - Additional Factors

• Areas with severe cardiac issues or circulation problems
• Areas with heat sensitive skin or skin damage
• Areas with edema
• Reproductive organs (e.g. testes)
• Recent radiation treatments
• Use of liniments or hot packs immediately before therapy
• Patients with communication barriers that interfere with therapist evaluations

Precautions to Thermotherapy

• Areas near the eyes or over the eyes
• Anterior neck and carotid sinus
• Pregnant women
• Patients with impaired circulation
• Heat-sensitive skin disorders or skin wounds
• Patients with cardiac conditions
• Fluidotherapy use in consideration of potential allergies.

No Contraindications/Precautions

• Intact skin overlying implants containing metal, plastic, or cement
• Areas over electronic devices.
• Areas near chronic wounds.
• Superficial or regenerating nerves.
• Areas on the head, chest, or heart.
• Active epiphyses (with appropriate supervision and monitoring).
• Patients with hypertension (with appropriate evaluation and monitoring).

General Method for Application

• Comprehensive patient evaluation including history, comorbidities, and age.
• Establishment of appropriate goals for intervention.
• Removal of jewelry and clothing.
• Patient comfort.
• Application of the modality.
• Ensuring safety features like a call button.
• Post-treatment inspection and documentation.

Safety - HPSO 2020 Report

• Data from 2015−2019, showing 16.1% of claims related to improper performance of biophysical agents, with injury during electrotherapy, heat therapy, and hot packs being the most frequent.

Clinical Decision-Making - Heat vs. Cold

• Diagnostic, medical status, and objective findings must be considered.
• Only one heating modality per session is ideal.
• Consideration of the stage of injury/disease (acute=cold or chronic=heat)
• Appropriate body region for therapy
• The needs of the patient.

Heat vs. Cold - Advantages and Disadvantages

• Heat Advantages: Pain reduction, improved extensibility, decreased stiffness. Disadvantages: May increase swelling.
• Cold Advantages: May decrease swelling and pain. Disadvantages: Reduction in extensibility and potential for stiffness.

Clinical Decision-Making - Superficial vs. Deep Heat and Wet vs. Dry Heat

• Superficial heating modalities (e.g., moist heat) are typically for superficial tissues.
• Deep heating modalities (e.g., ultrasound) are used for deeper tissues.
• Wet heating pads frequently involve temperature retention in the treated area.
• Dry modalities like the hydrocollator do not necessitate the same level of monitoring. The choice depends on the specific treatment.

Assessment of Effectiveness and Expected Outcome

• Evaluation of pain, range of motion, muscle guarding, and functional movements following a treatment session.
• Documentation of modality used, method of application, treatment duration, body area, patient position, and any special precautions.

Thermotherapy to Increase ROM

• Heat application is routinely used before or during stretching and mobilization procedures.
• Application of superficial heat in conjunction with static stretching often improves range of motion in joints. In many cases, deeper heating may be necessary.

Thermotherapy in Tissue Healing

• Studies of superficial heat on tissue healing are limited. (and not well established).
• Heat increases tissue metabolism, which assists with the healing process.

Thermotherapy in Pain Management

• Heat increases blood flow and supplies nutrients while removing pain-inducing chemical mediators.
• Improves soft tissue extensibility and may decrease soft tissue tension.
• Improved patient movement may further improve patient perception of pain reduction.

Clinical Scenario (repeat)

• The patient is a 55 year old male with severe stiffness in the left shoulder and limited range of motion, especially with elevation. The onset was gradual over 6 months. The goal is to improve shoulder stretch.

Clinical Decision-Making

• Questions to ask when making decisions related to treatment include: Does the patient have a dysfunction or limitation, that can be improved using thermotherapy? Is the patient appropriate for thermotherapy? What specific goals can be achieved with use of the modality? What specific form of thermotherapy is appropriate in this case? What parameters for that form of thermotherapy are appropriate?

Summary

• Use clinical judgment to select an appropriate heating modality.
• Consider indications, past medical history, the body area to be treated, contraindications, precautions, patient preferences, and also if the modality is superficially or deeply focused.