Therapeutic Interventions Week 9 - Cryotherapy and Heat

Cryotherapy: Physical Principles

• Cryotherapy involves using cold modalities for therapeutic purposes.
• It lowers tissue temperature, decreasing blood flow and tissue metabolism to minimize bleeding and acute inflammation.
• Application methods include cold packs, ice massage, cold baths, compression devices, hypercooled air, and vapocoolant sprays.
• Caution should be taken with individuals who have cold hypersensitivity, impaired circulation, diminished sensation, or high blood pressure.

Conduction

• Cooling is achieved by removing heat from an object.
• Conduction involves heat transfer through direct interaction of molecules.
• Commonly used conductive cooling methods include ice or cold packs and extremity immersion in cold water.
• The greater the temperature difference between the skin and the cooling source, the greater the tissue temperature change.

Convection

• Convection happens through direct contact between the skin and moving fluid particles.
• A cold whirlpool uses convection by moving water over the patient’s skin.
• Heat removal occurs faster with convection because new cooler molecules are continuously introduced to the skin surface when movement is occurring.
• Water's specific heat results in 25 times greater heat loss.

Evaporation

• Vapocoolant sprays use evaporation for energy transfer.
• As a liquid leaves the canister and evaporates, it cools and extracts heat upon contact with the skin
• This causes a reflexive reduction in motor neuron activity and allows the tissue to stretch more easily.
• Skin temperature can drop rapidly, but changes in subcutaneous tissue and muscle temperatures are negligible.

Factors Influencing Response

• Temperature difference between the cold object and the soft tissue
• Exposure time to cold therapy
• Thermal conductivity, with metals being better conductors than plastic
• Adipose tissue acting as an insulator
• Type and size of the cooling agent
• Total body surface area
• Activity level
• Ability of cooling agent to maintain its temperature

Heat Exchange

• Heat exchange occurs between an artery and a vein.
• Following heating, an artery vasodilates to carry away heat.
• Following ice application, an artery vasoconstricts.
• After ice pack application, tissue temperature can take over 60 minutes to return to resting values.

Biophysical Principles of Tissue Cooling

Temperature Changes During Ice-Pack Application

• Ice therapy reduces swelling and controls pain by lowering tissue temperature.
• Skin temperature changes occur rapidly.
• Lowering skin temperature to 56.5°F produces a local analgesic effect.
• A temperature of 50°F can produce a 33% reduction in nerve conduction velocity.
• Deeper tissues take longer to cool.
• Crushed ice lowers skin surface temperatures the best.
• Ice massage reduces intramuscular temperature greater than ice bags.

Physiological Changes From Reduced Tissue Temperature (Hemodynamic Effects)

• Cold decreases histamine and bradykinin, causing vasoconstriction.
• It increases smooth muscle tone and blood viscosity, decreasing blood flow.
• Reduction in skeletal muscle spasm can reduce pain and muscle spindle afferent sensitivity.
• Muscle performance can be temporarily enhanced with short duration cold.
• Cold increases tissue viscosity and decreases tissue elasticity, leading to joint stiffness.

Posttraumatic Edema and Inflammation

• Cold is the modality of choice for the first 24-48 hours after injury.
• Immediate cooling can reduce secondary tissue damage.
• Moderate cooling can limit the extent of swelling.
• Intense cold or prolonged cold application can lead to greater swelling formation.

Peripheral Nerve Effects

• Cold increases the threshold for depolarization.
• It slows nerve conduction velocity, and extreme cold can block nerve conduction.
• Decreased nerve conduction velocity in sensory nerves is desirable for facilitating pain reduction.
• Caution should be observed when cold is applied in the area of nerve tissue because of the risk of nerve injury or damage.

Muscle Performance Effects

• Cooling agents can affect the ability of a muscle to generate tension.
• Decreased muscle temperature and muscle strength can be a result of reduced muscle blood flow.
• Caution needs to be taken if strenuous exercise or athletic activities are going to be performed after ice or cooling application
• Ice therapy can also affect proprioception.

Neuromuscular Effects

• Cold can temporarily decrease the amplitude of deep tendon reflexes and frequency of clonus.
• Cold can facilitate alpha motor neuron activity and decrease gamma motor neuron firing
• Local or regional cooling can be beneficial to individuals with some neurological conditions.
• It should be noted that many individuals with spasticity report a worsening of symptoms when they become cold.

Cryotherapy: Indications, Guidelines, and Contraindications

Clinical Indications for Cold Therapy

• Acute musculoskeletal trauma
• Postsurgical pain and swelling

Guidelines for Cryotherapy

• Acute phase in 24 to 48 hours that cold is the modality of choice.
• Cold is often used in conjunction with rest, compression, and elevation in managing acute trauma.
• Represented as the acronym, R.I.C.E.(rest, ice, compression, elevation)
• Goals of cold therapy are to reduce swelling and inflammation, prevent further injury, and return to functional activities as soon as possible.
• Less intense cold applied for durations of 20-30 min appears to be a logical choice.
• The use of compression increases the rate and degree of cooling.
• Compression can help prevent and reduce swelling by increasing external pressure on the tissue
• Continual compression can often be provided in the forms of braces, wraps, or cold compression devices.
• Cooling the skin can elevate a patient’s pain threshold and reduce the pain.
• DOMS studies have shown no significant benefit for using cold to reduce DOMS
• Vapocoolant spray and stretch techniques are widely used but very few studies support its benefit in treating myofascial trigger points
• Watch for signs of hypersensitivity.
• Signs of hypersensitivity include hives and wheals.
• Avoid stresses that could potentially reinjure or aggravate for 1-2 hours

Common Sensations Due to Cold

• May initially feel intense cold followed by burning, then aching, then numbness
• Generally, conductive cooling is 20-30 min.
• Intermittent cold applications are more effective than a single 20-min application.
• Cycling of the cold rather than repeated prolonged use is suggested to avoid or reduce the occurrence of any adverse responses to nerves or blood vessels.

Selecting a Cooling Agent

• The choice of a cooling agent depends on its accessibility, the body part to be treated, and whether simultaneous compression and elevation are needed.
• Ice or ice plus water applied directly to the skin provides superior cooling, compared to commercial gel packs or packs of frozen peas.

Contraindications for Cryotherapy

• Cold urticaria
• Cold intolerance
• Paroxysmal cold hemoglobinuria
• Cryoglobulinemia
• Raynaud's disease or phenomenon
• Over a regenerating peripheral nerve
• Over an area of circulatory compromise

Precautions for Cryotherapy

• Hypertension
• Thermoregulatory disorders
• Over a superficial peripheral nerve
• Over an open wound
• Over an area of poor sensation
• In the very young or very old
• With individuals with poor cognition
• Persons with aversion to cold

Evidence – Clinical Practice Guidelines

• For lateral elbow pain and muscle function impairments = cryotherapy can be used to reduce pain

Cryotherapy: Methods and Assessment

Methods of Providing Cryotherapy

• Homemade ice bag
• Homemade cold pack (with alcohol)
• Ice/cold bath
• Commercial cold packs (gel)
• Cold compression units

Cold Packs

• For any agent that has the ability to reach temperatures below 30 degrees Fahrenheit, damp towels around the skin are recommended.
• Ice is the most effective type of cold.
• Commercial gel packs require a layer of damp towels.
• A mixture of water and isopropyl alcohol can also be used as a homemade cold pack.

Ice Massage

• Usually performed over a small area or over trigger points before deep pressure release or massage.
• The ice is slowly rubbed on the skin using the small overlapping circles or strokes.
• Analgesia is experienced during treatment.
• Skin temperature will usually not drop below 59 degrees Fahrenheit when the ice is continuously moved over the skin

Vapocoolant Spray

• Can be used to treat trigger points and induce relaxation of tight muscles before stretching.
• Canister sprayed 12-18 inches away from the skin on the target muscle.

Manual and Electric Cold Compression Units

• Can allow for manual circulation of cold water through a cuff that’s applied to an extremity.
• Specific temperature monitoring and adjustment are not possible with manual units.
• Continuous cold compression units use an electric pump to circulate the cold water.
• Pain, swelling, range of motion and medication were improved to a greater extent in patients who used continuous cold compression versus ice packs.

Cold Baths

• When cooling the distal extremities, immersion of the body power into a cold bath is the most practical.
• Water temperatures for immersion vary from 50 degrees Fahrenheit to 64.4 degrees.
• Movement of water particles over the skin, either with water turbulence or with movement in the body part will increase the speed of cooling.

Cold Gel

• Most use chemicals such as ethanol or methanol as the active cold forming agents.
• They are applied to the skin overlying the area of injury and pain.

Assessment of Effectiveness

• Edema – girth measures, volumetrics
• Pain – pain scales, questionnaires
• Range of motion – goniometric measures
• Functional movements – observation of gait quality, ease of AROM
• Muscle guarding – joint ROM, muscle flexibility measures

Therapeutic Heat: Physical and Biophysical Principles

Physical Principles of Heat

• Heat flow through tissues varies with the tissue type.
• The greatest elevation with a heating modality occurs in the skin and the subcutaneous tissues within a 2.5 cm of the skin surface.
• Individuals with a high body fat have impaired heat transfer to muscle using superficial heat.

Heat Transfer

• Conduction is a method of heat transfer where the kinetic motion of atoms and molecules of one object is passed to another object.
• Convection is the bulk of movement of moving molecules.
• Radiation is a conversion of heat energy into electromagnetic radiation.

Factors Influencing Response

• Extent of temperature increase
• Rate at which energy is added to the tissue
• Volume of tissue exposed
• Tissue composition
• Capacity of the tissue to dissipate heat

Tissue Temperature

• To meet therapeutic levels of vigorous heating, study results indicate tissue temperature must be elevated to between 104 and 113 degrees Fahrenheit.
• Skin changes first, then subcutaneous tissue, then muscle tissue.
• Dry heat can elevate surface temperatures to a greater degree, but the moist heat can elevate the temperature to a slightly deeper level.

Biophysical Effects of Temperature Elevation

• Tissue should be elevated to 104-113 degrees Fahrenheit to provide a therapeutic effect.
• Increased cell activity and metabolic rate will occur.
• Tissue temperature must be elevated to between 104-113, at which point hyperemia, which is increased blood flow, will occur.

Neuromuscular Effects

• The underlying basis for use may relate to the ability of heat to elevate the painful threshold, alter nerve conduction velocity, and change muscle spindle firing
• Heating over the area of a peripheral nerve can elevate the pain threshold.
• Heat can also be used to help with muscle spasms.

Connective Tissue Effects

• Increases elasticity and muscle flexibility
• Decreases viscosity
• Decreases joint stiffness
• The viscous properties of connective tissue permit the residual elongation of connective tissue.
• Greater residual length changes will occur when the stretch is applied during the time that the tissue is elevated to the therapeutic levels between 104-113 degrees Fahrenheit.

Therapeutic Heat: Indications, Guidelines, and Contraindications

Clinical Indications

• Reduction of pain, stiffness
• Decrease muscle spasm
• Increase ROM
• Improve tissue healing

Guidelines for Therapeutic Heat

• Tissue should be elevated to 104-113 degrees Fahrenheit
• Intervention time varies from 15-30 minutes
• Skin overlying the area of intervention should be tested for thermal sensation using hot and cold water

Contraindications for Therapeutic Heat

• Areas with lack of intact thermal sensation
• Vascular insufficiency or vascular disease
• Recent or potential hemorrhage
• Known malignancy
• Acute inflammation
• Infection
• Liniments or heat rubs recently applied

Therapeutic Heat: Methods and Assessment

Thermal Modality Options

• To increase tissue temperature 1-3 cm depth uses moist heat packs and paraffin wax bath.
• To increase tissue temperature 1-5 cm depth uses continuous ultrasound.

Conductive Heat Modalities

• Dependent on thermal conductivity of the tissues, body volume exposed and time of exposure.

Moist Heat Pack or Hot Packs

• Stored in a thermostatically controlled cabinet at a water temperature between 158-167 degrees Fahrenheit
• Should be covered in layers of terry cloth toweling or hot pack covers.
• Moist heat packs should be inspected regularly for leaks

Advantages of Hot, Moist Packs

• Ease of preparation and application
• Variety of shapes and sizes

Disadvantages of Hot, Moist Packs

• No method of temperature control once it's applied to the patient
• Doesn’t conform to all body parts

Paraffin Wax

• Used for distal extremities like hands or feet
• Usually a mixture of about six or seven parts paraffin wax and one part oil.
• Extremities to be treated should always be washed and dried and all jewelry should be removed from the part
• Dip and wrap or dip and re-immerse are the techniques to use to apply paraffin wax

Advantages of Paraffin

• Molten state allowing for even distribution to the areas around the hands or feet
• Oil helps moisturize the skin.

Disadvantages of Paraffin

• Can only be used for distal extremities
• No method of temperature control once applied

Electric Heating Pad

• Method of applying a low level heat over a long period of time

Disadvantages of Electric Heating Pad

• Patient must be near an electrical outlet
• Passive intervention

Advantages of Electric Heating Pad

• Has an adjustable intensity control
• Readily available for purchase and reasonable cost

Air-Activated, Wearable Heat Wraps

• Made of cloth embedded with multiple discs of iron powder, activated charcoal, sodium chloride, and water.
• Can be worn up to 8 hours at a time.
• Wraps maintain a temperature of about 104 degrees Fahrenheit.

Disadvantages of Wearable Heat Wraps

• Can be only used once

Advantages of Wearable Heat Wraps

• Comfortable low profile heat source

Fluidotherapy

• Dry heat modality that transfers heat energy by forced convection.
• Solid particles become suspended when the air is forced through them, making the fluidized bed behave and demonstrate properties similar to liquid.
• Treats more distal extremities like the hands or feet.
• Temperatures for intervention usually range from 102 to 118 degrees Fahrenheit
• Wounds can be protected with a plastic barrier or a bag.

Advantages of Fluidotherapy

• Can be convenient and easy to administer
• Temperature of application and agitation can be controlled

Disadvantages of Fluidotherapy

• Relatively expensive to purchase
• May feel claustrophobic

Clinical Decision Making

• Cold is usually preferred during acute stages of inflammation.
• Heat can be better tolerated physiologically by many individuals with pain or muscle spasm.
• Heat to distal extremity seems to be tolerated better than cold.

Assessment of Effectiveness

• Pain – pain scales, questionnaires
• Range of motion – goniometric measures
• Functional movements – observation of gait quality, ease of AROM
• Muscle guarding – joint ROM, muscle flexibility measures

Light Therapy

Light Therapy

• Light rehab includes UV light, light-emitting diode (LED) and Laser.
• Stands for light amplification by stimulated emission of radiation

Physical Properties of Lasers

• Properties of monochromaticity and coherence of laser light allow the light energy to be concentrated
• Laser energy density is measured in Joules per cm.
• Coherence is a property unique to laser light.
• Refers to the property where all light waves within a laser beam are in phase with each other

Physiological Effects of Lasers

• Chromophores, photosensitive molecules within the membrane of cells and organelles.
• Mitochondrial chromophore stimulation can increase the respiratory chain activity and enhance ATP synthesis.
• High intensity laser therapy was also reported to improve diabetic and neuropathic foot ulcers by increasing blood flow.
• Low level laser has been shown to modulate various chemical mediators of pain, including a pain associated with inflammation

Instrumentation and Clinical Application

• Low level lasers are classified by the FDA as Class 3B lasers.
• High intensity lasers are classified as Class 4 lasers.
• Require the patient and clinician to wear eye protection to prevent retinal damage.

Techniques Include

• Direct skin content of the applicator probe over the structures to be treated
• For larger areas, a grid may be used to ensure uniform treatment requiring multiple points of irradiation.
• Laser energy delivered to a tissue for both low laser light therapy and high intensity light therapy are calculated the same way

Indications for the Use of Lasers

• Pain and inflammation associated with musculoskeletal conditions.
• Chronic skin wounds.
• Patients with mild to moderate carpal tunnel syndrome may also benefit from low light laser therapy.

Precautions

• Impaired sensation
• Indirect eye exposure
• Skin color

Contraindications

• Direct eye exposure
• Pregnancy
• Active malignancy
• Active hemorrhage
• Open growth plates
• Endocrine system

Evidence – Clinical Practice Guidelines

• Clinicians may use laser therapy for individuals with lateral elbow pain and muscle function impairments
• Clinicians should use low-level laser therapy for heel pain due to plantar fasciitis