Exam 2: Deep Thermal Agents

Deep Heating Agents

Heat Tissues at depths up to 5 cm

Common modality used to deliver deep heat:

- Therapeutic Ultrasound (US)

- Phonophoresis

- Short Wave Diathermy (SWD)

Physical Principles: US

- US machine produces a high frequency alternating current at 1-3 million cycles per second (MHz)

- The alternating current travels through the coaxial cables into the transducer head

Transducer

- Houses a vibrating piezoelectric crystal and converts electrical energy into ultrasonic or acoustic energy

- The vibration of the crystal generates sound waves which are transmitted to a small volume of tissue

- This causes molecules within the tissue to move

US travels poorly through

air

- so a lubricant must be used to maintain contact between the transducer and the tissue, ensuring that the energy is dispersed into the tissue

Deep Heating Agents: Ultrasound

Acoustic energy (sound waves) used in medicine for diagnosis and in rehabilitation to help restore and heal soft tissues

Inaudible high frequency acoustic vibration that produces thermal and/or nonthermal (mechanical) physiologic effects on tissue (over 20,000 Hz)

Effects of US

Thermal Effects (heating deeper tissues with high collagen content)

- Biophysiological changes produced by cellular heating

Nonthermal Effects (tissue healing and repair)

- AKA: mechanical effects

- Biophysiological changes produced by the cellular effects of

-- Cavitation

-- Microstreaming

-- Acoustic streaming

Both Thermal and Nonthermal US can be used to facilitate healing and occupational functioning

Longitudinal Wave

When the sound waves are generated rapidly and dispersed into the tissue, the molecules in the waves' path are pushed back and forth by the alternating phases of successive waves until the wave runs out of energy

A wave moving in one direction and compressing and decompressing the molecules in its way

Shear Wave

When the wave encounters bone, the sound energy is transferred along the periosteum and is then deflected up at a right angle causing a shear wave

Shear waves occur when the sound energy strikes a solid substance

This may cause heating of the outer covering of the bone but is negligible in terms of tissue temperature elevation

Never do US on dorsum of hand (not deep enough) and will cause this

Waves deflect back off bone which can cause a deep burn

Standing wave

Occurs when the sound head is not moved adequately and the incoming sound waves encounter the reflected sound waves moving back up toward the surface

This can create hot spots and potential overheating of tissue

Each tissue in the body transmits and absorbs ultrasound energy according to its

unique properties (absorption coefficients)

- The rate at which the sound wave travels depends on the density of the molecules of the tissue

Low impedance vs high impedance

Low Impedance

- Body fluids such a blood and water have the lowest impedance and lowest acoustic absorption coefficient (adipose tissue, muscle tissue, nerve, blood and blood vessels)

High impedance

- Bone and other protein dense structures (scars, joint capsules, ligaments, tendons, bone, fascia) possess high impedance and absorption coefficients

- Tissue with high impedance are good absorbers of US energy

US doesn't work well for low impedance

Note bone has high impedance but we don't want the bone absorbing this

US is absorbed into tissue, causing tissue molecules to

rotate and bounce

- This results in thermal or nonthermal effects depending on parameter settings

Ultrasound (US) parameters

Frequency

Intensity

Duty Cycle (continuous vs pulsed)

Time

Treatment goals (thermal vs nonthermal)

Area being treated

Frequency

The number of times per second that the crystal changes shape

Frequency determines the depth of penetration and rate of heating

- 1 MHz: depth of penetration = 2.5-5cm

- 3MHz: depth of penetration = surface-2.5cm

(Heats 3x faster than 1 MHz)

The spread of US waves into tissue is affected by

the frequency (produced by the generator) and size of the crystal (mounted inside the transducer head)

Intensity

Intensity of the beam of energy varies within the sound wave: beam nonuniformity ratio (BNR)

BNR is a measure of the homogeneity of the therapeutic US wave

Crystal performance is measured in beam non-uniformity ratio (BNR)

The intensity of the beam of energy is a significant factor in determining tissue response

*how much ultrasound

and how consistent is it diving down into the tissues*

Important consideration with intensity and the transducer head

IMPORTANT to keep the sound head (transducer) moving to avoid hot spots

In general, there is greater tissue temperature elevation with

higher intensities

Intensity is documented as

watts per square cm (W/cm²)

0-2.5 W/cm²

can go up to 2.5 W/Cm2 (but Kate said she never got this high, she said her highest was 1.5)

US energy will decrease as it passes through

different layers of tissue

- This is related to the absorption of energy by tissue and the scattering of the beam

Continuous US vs Pulsed US

Continuous US

- 100%

- the whole time you are doing ultrasound, waves are on 100% of the time

is going to create a thermal effect

Pulsed US

- could vary (20%, 50%)

- so like for 20%, waves are only going for 20% of treatment time and off 80%

- 20% duty cycle is the most common setting for pulsed US to achieve nonthermal effects

Duty Cycle (Pulsed or Continuous)

Amount of time the US is on

Use depends on the pathology, stage of wound healing, and area being treated

Determines the overall amount of acoustic energy a patient receives (on-time of US)

Continuous (100% duty cycle)

- Sound wave and energy are constant or continuous

Pulsed

- A percentage or ratio of time that the US energy is actually being introduced in the body

Duration for US

(0-16 minutes)

- Typically 8-15 minutes per treatment

Depending on treatment parameters and size of the area to be treated

Number of treatment sessions will vary based upon patient characteristics and goals of treatment

can't bill for heat or ice but can bill for US

Thermal US

US is a deep heating agent capable of elevating tissue temperatures to a depth of 5cm

Typically achieved with continuous (100% duty cycle)

Thermal Effects

Patients should feel gentle warmth with thermal treatments

Avoid in areas with bone or minimal muscle mass

3 MHz heats faster than 1 MHz so treatment times will be longer at the same intensity level with 1 MHz in order to obtain the same desired increase in tissue temperature

Indications for use of Thermal US

Pain reduction: chronic trigger points, muscle spasms

Increase ROM: Collagen remodeling

- Use prior to stretching of adaptively shortened tissues

- Joint capsule, tendon, scar tissue

Increase blood flow

Decrease viscosity of fluids

Thermal Dosage Parameters

- Continuous

- Delta T of 1-2 degrees C

- Treatment time 8-15 minutes

- Use comfortable output

- Treatment area is twice the head size

- Monitor patients' thermal sensation

- Do not use in desensitized areas; instead use subthermal

Nonthermal US

Exerts mechanical effects at the cellular level such as:

- Increased skin and cellular permeability and diffusion

- Does not elevate tissue temperature/generate heat

- Duty cycle of 20% (20% on, 80% off)

can be used at any stage of healing

Tissue Effects: Nonthermal US

Promotes healing of soft tissues (tissue inflammation)

Aids in bone healing

- different frequency than what we are talking about

Effective in wound care

- around the wound (obviously not in the wound)

Structural changes in the cell membrane

Increased cell membrane permeability vs continuous US

Destabilization of the cellular membrane

- More molecules are able to enter the cell and facilitate increased intercellular calcium and protein synthesis and release of histamine (histamine can facilitate resolution of the inflammatory phase of healing)

Tissue Effects: Nonthermal US cont...

Supports the inflammatory process by promoting mast cell function and macrophage activity, promoting serotonin release' augments chemotaxis

Activates fibroblasts and collagen formation in connective tissues

Increases synthesis of nitric oxide in endothelial cells (vasodilation and increased blood flow)

Improves blood flow in healing fractures (beyond our scope)

Stimulates proteoglycan synthesis in cartilaginous tissue

Subthermal Dosage Parameters

Everyone has a different definition of subthermal → always specify what the person means if they say they used subthermal

20% duty factor with pulse rate of 100 PPS

See chart located on equipment

When using thermal level US

nonthermal effects are likely taking place as well

EBP Indications for Nonthermal

Soft tissue trauma-pain

- Reduces pain, increase local circulation, tx over edematous tissues, increase cell permeability

Rheumatoid Arthritis - pain

- Increase strength & ROM, decrease edema

Muscle tone - spasm reduction

- Treat both agonist and antagonist GTO, stimulate GTO to inhibit muscle tone

Thermal US Effects

Increases extensibility of collagen fibers

Decreases muscle stiffness

Reduced muscle spasm

Alters nerve conduction velocity/diminishes pain perception

Increases metabolism and blood flow

Provides all of the effects of nonthermal US

Nonthermal US Effects

Increases phagocytic activity of macrophages/attracts immune cells to tissue

Increases protein synthesis

Increases capillary density

Regenerates tissue

Heals wounds

Clinical Use of US

Location/Anatomy involved

Stage of healing

Depth

Area

Type of tissue to be treated:

Ex: Lateral Epicondylitis

- Best treated with 3 MHz b/c it's a superficial condition

Ex: Upper Trap pain

- Best treated with 1 MHz b/c it's a deeper condition

The size of the treatment area should be limited to

2x the size of the sound head

Coupling Medium

Lotion or gel (at least 1/8 inch-more if client is hairy)

- Apply enough pressure to provide contact with gel without displacement of gel

Transducer movement should cover approximately

4cm/sec using back and forth or circular strokes

- Face of sound head should be kept flat to decrease US reflection

US intensity should be decreased if

patient reports any pain or sensation of deep aching or during treatment

Water immersion is appropriate for

small areas

- Water used vs lubricant

- Will not go into depth in this class with this treatment application

Phonophoresis

Use of US to facilitate the delivery of topically applied drugs or medication to selected tissue

Requires physician order to use medication

Different delivery of Ultrasound

- Using ultrasound to drive medication into the skin

Questionable evidence regarding its effectiveness of phonophoresis

Anti-inflammatory

- Hydrocortisone cream

- dexamethasone sodium phosphate sonic gel mixture

Analgesics

- 100% Flexall or 25% Flexall and 75% US gel

What percent pulse for phonophoresis

Ultrasound at a 50% pulse is best for medication

- more effective than 100 and 25

- however, this does give a mild thermal effect → so keep that in mind

Phonophoresis is a noninvasive use of therapeutic ultrasound to facilitate

the delivery of topically applied drugs, most frequently corticosteroids, hydrocortisone acetate, and dexamethasone sodium, as well as other medications such as erythromycin and lidocaine.

Phonophoresis actively transports the medication into

the underlying targeted tissue through both a thermal and nonthermal mechanism.

Transmissivity of ultrasound is directly related to the conducting gel being utilized, with wide variability

Medication stays more localized in the area being treated rather than having a systemic effect.

Many of the popular analgesic creams, such as Bio-Freeze (Performance Health) and Flexall (Chattem), are used as coupling agents with the intention of

decreasing pain perception.

Warnings with US/Phonophoresis

Do NOT use when there is:

- Severe infection

- DVT

- Cancer

- Do not apply directly over epiphysis of growing bones, eyes, heart, testes

- Do not use with Pacemaker

- Do not use directly over implants

- Do not use directly over anterior neck, carotid sinus, vagus nerve, laryngeal or pharyngeal muscles

- Do not use with diathermy

- Do not use directly over abdomen

- Do not use directly over exposed spinal cord (i.e. post laminectomy or spinal fusion)

US Precautions for phonophoresis and US

Unhealed fracture sites (high does US)

Over breast implants

Patients with impaired cognition or mentation

Over regenerating peripheral nerves

Early stages of tendon or ligament repair

Marked demineralization or osteoporosis

Plastic and metal implants

Drug allergies (phono)

Rx precautions

Children

Active bleeding

Hypersensitivity and/or Impaired Sensation

Pain during recent treatment

Medicated patches, salves, creams

Hot/cold packs in conjunction

Over areas of acute inflammation

US Contraindications for phonophersis & US

Suspected DVT

Over exposed CNS tissue (laminectomy, spina bifada)

Over bone cements or plastic implants

Over implantable-type diffibrillator

Bleeding and edema; areas with a tendency to hemorrhage

Reduced sensation or if a person cannot report heat sensations accurately

Very old/very young: due to compromised body temperature regulation

Skin or lymphatic cancers; tumors or malignancies

Over a cardiac pacemaker or surrounding adjacent tissue

Pregnancy (over low back, abdomen, pelvis areas)

Infected areas

Epiphyses of growing bone (high intensity needs to be less than 1.0 W/cm²)

In conjunction with radium or radioactive isotopes treatment for cancer within 6 mos

Over the heart, eyes, testes (reproductive organs)

Over carotid sinuses and cervical ganglion

Over spinal column or inadequate protection over spinal cord

Considerations Prior to Use (PHIMM)

Pregnancy

Hemorrhaging/Bleeding

Infection

Malignancy

Metal

Considerations cont...

Regularly check and monitor patient status during treatment

Check skin and prep skin prior and after

Check power cords prior

Cross contamination of US head between patients

Do not immerse any part of the operator's body into the water bath during underwater ultrasound therapy.

Underdosing US treatment may result in little to no therapeutic benefit

High-intensity continuous US can cause deep burns if US head is not moved constantly during treatment

- Most common over bony tissue

What will US feel like to the patient

Shouldn't really feel anything but waves are vibrating tissues to bring good things in and take the bad out

- with thermal, we will tell them heat will help with muscle soreness hopefully

Electromagnetic Radiation (EMR)

Synchronized oscillations of electrical and magnetic fields

Used in rehab settings to expedite the healing of soft tissues or relieve pain

Low-frequency EMR

Nonionizing radiation and can be used therapeutically

- Shortwaves

- Microwaves

- Infrared

- Visible light

- UV A and B

High-frequency EMR

Ionizing radiation

Able to break molecular bonds and form ions

- X-rays, gamma rays

- Used for imaging

- Used to destroy pathological cells

- Not used in the rehabilitation setting

SWD: What Does It Do??

Electromagnetic energy is converted to thermal energy

Produces thermal and non-thermal (mechanical) response with physiological and therapeutic effects

Purpose of short wave diathermy

To significantly heat larger areas of deep tissue with minimally affecting superficial tissues

Average power output of over 38 watts will cause tissue temperature to increase

- Thermal

- Nonthermal

Heats deeper tissues compared to a superficial heating sources such as a moist hot pack

Heats larger and deeper areas compared to US

Short Wave Diathermy (SWD) breakdown

Diathermy: Greek word meaning "through heat"

Shortwave: refers to the shortwave electromagnetic band of the electromagnetic spectrum. High frequency but short in wavelength

Short Wave Diathermy (SWD)

Application of high radiofrequency current/electromagnetic field to underlying tissue

Deep heating is caused by the conversion of energy into heat as it passes through tissue, due to the resistance of the tissue to the passing of the energy

Heating of deeper structures can be obtained through the application of high frequency electrical currents

Different frequency ranges will affect specific tissue types at different depths

The advantage to SWD is that the overall area that can be heated will be larger than those covered by a hot pack or US

can also do non thermal setting

Application of SWD: Induction is the most common method of application

The drum is placed over the treatment area and with the flow of electrical current in the coil produces a magnetic field and current in the tissue

Tissue that offers the greatest resistance to current flow develops higher levels of heat

Subcutaneous fat and tissue that has a high fat content insulates and resist the flow of electrons and have a tendency to overheat

Pulsing the signal allows the tissue to cool as the heat dissipates during the off cycle of the pulse

Uses coils housed in a drum

Produces both electrical and magnetic energy (ratio of one to the other depends on type of machine)

Electrical field

Charged ions in the tissue move from one pole to the other

Magnetic field

A conductor is exposed to a changing magnetic field that causes circulating flow of electrons

SWD can be delivered in either a continuous or pulsed mode

Continuous

- Heats tissue to a depth of 2-5cm

Pulsed

- Non-thermal effects

SWD Physiologic Effects: thermal effects

Shortwave diathermy heats large, deeper tissues

Often used for pain control and to improve soft tissue extensibility

SWD Physiologic Effects: nonthermal effects

Pulsed diathermy

Often used for tissue healing and repair

Physiologic effects believe to bed related to cell functions:

- Changes cell membrane permeability

- Changes in protein structure and transport across membranes

- Acceleration of ATP synthesis and action by cells

SWD is not capable of producing

depolarization and contraction of muscle because the wavelengths are too short

Therefore the primary effects of SWD are thermal

Vasodilation

Reduced pain

Increased soft tissue extensibility

The high frequency energy creates a vibration of molecules which in turn produces heat

Control for treatment are not precise, so it is impossible to accurately measure or Rx the amount of heating the patient will receive

The amount of heating is determined by the current density and resistance of the tissue being treated.

Thermal SWD Dosage Parameters

10-33% duty factor with pulse rate of 800 PPS and pulse duration between 100-400 uSEc

10-40 watts of average power, Peak 150 watts

20 minute treatment duration

Treatment area is drum size

Monitor for thermal sensation

Do not use with desensitized areas.

Non-thermal Effects of SWD

Electromagnetic energy allows damaged cells to return to their normal function

Non-thermal effects occur at the cell membrane as the electromagnetic energy affects ion attraction and cell function (cell membrane function)

Restores the normal function of damaged cells through repolarization

Increases cell growth and division

Increases microvascular circulation

Modulate pain

Modulate inflammation

Augment tissue healing (including bone tissue)

Improve perfusion to microvasculature to facilitate wound healing

looks very similar to ultrasound

Subthermal SWD Dosage

4% duty factor with pulse rate of 400 PPS and duration of 65uSec

150 watts is peak output power

Average power is 3.9 watts

30 minute treatment duration

Treatment area is the drum size

Subthermal SWD Indications

Subthermal typically means non-thermal or subthermal effect

Post traumatic / surgical

- Post/op pain reduction

- Post traumatic pain and edema reduction

Osteoarthritis pain reduction

Increasing circulation to improve tissue healing

- Ligament

- Cartilage

- Wound

Muscle

Why can wound can be performed better with diathermy

can't use ultrasound since you have to touch skin

but with diathermy → don't have to touch skin so works for wound (non-thermal level)

Physiological Effects of SWD

Increased tissue temperature

Increased blood flow

Increased membrane permeability

Increased enzymatic reactions

Increased metabolic rate

Tissue extensibility

Decreased joint stiffness

Increased pain threshold

Facilitation of tissue healing

Application Technique of SWD

Pt needs to remain still during tx

Use shower cap over drum for intermediate infection control applications

After tx, clean with disinfectant wipe

Drape exposed area with towel to absorb surface sweat in thermal application and for additional privacy and warmth.

Place center of drum directly over target tissue and towel.

Position drum within 1/8th of an inch from skin without touching the skin or towel.

Drum is not be in contact with skin: patient will either have a layer of clothing or a towel over skin

Pain Reduction Benefits of SWD

Post op -Treatment on the day of surgery significantly reduces the number of pain medications and length of hospital stay.

Post traumatic pain and edema - SWD accelerates the absorption of hematoma, decreasing swelling and bruising, reducing pain

Facilitates cartilage repair

Thermal SWD Indications

Pain reduction

- Subacute and chronic

Decreasing muscle tone: spasms

Circulation deficits

Increasing ROM: Collagen remodeling

- Joint capsule

- Muscle fascia

- Scar tissue

Reflection of the waves can lead to

hot spots and must be monitored for

SWD generates a high-frequency electrical current producing both

an electrical current and magnetic field within/around the treatment tissue

With SWD, the patient should only feel a

comfortable level of heat during the treatment

Treatment time for SWD

Treatment times vary between 15-20 minutes or up to a maximum of 30 minutes long to achieve desired physiological effects

Indications for SWD use

Heating joint structures

Decreasing stiffness

Increasing tissue extensibility

Improving blood flow

Decreasing pain

Indications for pulsed SWD

Facilitate tissue healing

Decrease edema

Decrease inflammation

Reabsorb hematomas

Decrease pain

SWD Contraindications

ALL WITHIN 10ft OF MACHINE

- Traumatic, acute inflammatory conditions

- Ischemia

- Pregnancy

- Application of areas of decreased sensitivity

- Metal implants (or within 10 ft of implant)

- Cardiac Pacemakers (or if individual with a pacemaker is within 10 ft)

- Implanted or transcutaneous neural stimulators (or within 10 ft of implant) (deep brain stimulator)

- Watches and jewelry should be removed prior to application

- Do not position patient on metal furniture during application of SWD

- Keep SWD units away from other medical equipment (TENS units, electrical units)

- Never apply SWD to eyes, testes, scrotum

- Epiphyseal plates of children

- Areas of malignancy

SWD Warnings

Directly over anterior neck, carotid sinus, vagus nerve, laryngeal or pharyngeal muscles

Do not use with monitoring equipment

Do not use with e-stim or within 5 ft of e-stim (some say 20 ft)

Do not use in proximity of electrical or magnetic equipment

Directly over abdomen

Do not use directly over metal in field

Directly over head and heart

Do not use directly over exposed spinal cord (i.e. post laminectomy or spinal fusion)

Severe infection

DVT

Cancer

Do not apply directly over epiphysis of growing bones

Eyes, heart, testes

SWD Precautions

Prescribing precautions

Children (just avoid this)

Active bleeding

Healing bones (thermal)

Hypersensitivity

Impaired circulation/sensation

Pain during treatment

Medicated patches, salves, and creams

Hot/cold packs in conjunction (avoid this too as desensitization can occur with cold and heat makes a double thermal)

Obesity (nonthermal)

Metal implants

Pregnancy

Skeletal immaturity

Excessive perspiration or we skin during treatment

Check skin and prep skin prior and after

Check power cords prior

Ensure proper head placement

Remove hearing aids

Do not apply to body if wet.

What should a patient feel with SWD

shouldn't feel anything on non-thermal but must sit still

with thermal should feel a MILD heat → anything more needs to be taken off

Can you perform ROM with patient during diathermy

no, must remain still

can fill time with questions, occupational profile type things, etc → we can't be doing movement

- sometimes the patient will need silence and relaxation during this time and that's okay too

If they start getting fidgety and trying concentrate when answering questions OR keep trying to gesture when talking to you → might need to be silent

Length of SWD

This PAM takes a long time (20-30 min) so keep that in mind if you only have a 45 min session → just have to consider what works best

- Weigh the benefit or is this something a hot pack could cover

- Have to prove this modality is preparing for occupation

Documenting SWD

have to document a PAM was used (even if it was only for 30 sec)

- have to say it was attempted and then not taken well

- that way others know not to try it again in the future

Could go in O & A → potentially P

O: how the skin looks

A: could say "patient appears to tolerate modality well"

P: do not recommend continuing with modality in future session