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Physical Medicine > 3) Deep Heating Agents: Ultrasound & Diathermy > Flashcards

3) Deep Heating Agents: Ultrasound & Diathermy Flashcards

1
Q

Ultrasound

A
  • Deep-penetrating agent
  • Mechanical or sound energy
  • Changes produces in tissue
  • Thermal
  • Non-thermal (mechanical)
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2
Q

Ultrasound is produced by

A
  • An alternating current flowing through a piezoelectric crystal housed in a transducer
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3
Q

Piezoelectric crystals

A
  • Produce positive and negative electrical charges when they contract or expand
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4
Q

The reverse piezoelectric effect (electropiezo effect)

A
  • Used to produce therapeutic ultrasound

- AC current is passed through a piezoelectric crystal resulting in contraction and expansion

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5
Q

Coupling method

A
  • Requires a coupling medium for energy to pass from the transducer to the tissues
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6
Q

Treatment area

A
  • Effectively exposed to the ultrasonic energy

- Limited to an area slightly larger than the diameter of the sound head

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7
Q

Near field (Fresnel zone)

A
  • Portion of the ultrasound beam used for therapeutic purposes
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8
Q

Ultrasonic output is described in terms of

A
  • Power
  • Frequency of the waves
  • Area that produces the power
  • Time
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9
Q

Frequency

A
  • Measured in megahertz (MHz)

- Most commercial therapeutic ultrasound units offer 1- and/or 3-MHz outputs

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10
Q

Low-frequency (1-MHz)

A
  • Divergent beam – deeper penetration ≈ 5 cm
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11
Q

High-frequency (3-MHz)

A
  • Collimated/focused beam – superficial ≈ 2.5 to 3 cm

- Energy is rapidly absorbed and heats three times faster than 1-MHz ultrasound

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12
Q

Power and intensity

A
  • Power is measured in watts (W)

- Intensity describes the strength of the sound waves at a given location within the tissues being treated

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13
Q

Spatial average intensity

A
  • Amount of energy passing through the sound head’s effective radiating area (W/cm2)
  • SAI = Total watts (W)/Effective radiating area (cm2) = W/cm2
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14
Q

Biophysical effects

A
  • The physiological changes within the tissues can be grouped into two classifications
  • Nonthermal
  • Thermal
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15
Q

Nonthermal biophysical effects

A
  • Changes within the tissues resulting from the mechanical effect of ultrasonic energy
  • Acute injuries
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16
Q

Thermal biophysical effects

A
  • Changes within the tissues as a direct result of ultrasound’s elevation of the tissue temperature
  • When thermal effects are desired
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17
Q

Duty cycle continuous output

A
  • Primarily thermal effects

- Used for tissues 5 cm or more deep

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18
Q

Duty cycle pulsed output (20%, 25%, or 50%)

A
  • Primarily nonthermal (mechanical) effects
  • Superficial (2-3cm)
  • ↓ the temporal average intensity, ↓ the thermal effects, and ↑ the proportion of nonthermal effects
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19
Q

Biophysical nonthermal effects

A
  • Interrelated events that produce the nonthermal effects (acoustical streaming, cavitation, microstreaming)
  • Increased fibroblastic activity and protein synthesis
  • Tissue regeneration
  • Reduction of edema
  • Bone healing
  • Pain modulation
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20
Q

Cavitation (non-thermal)

A
  • Formation of gas filled bubbles that expand & compress due to change in fluid pressure
  • Stable Cavitation (pulsating, results in an increased fluid flow around those bubbles/provides therapeutic benefits)
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21
Q

Microstreaming (non-thermal)

A
  • Unidirectional movement of fluid along the cell membrane causing mechanical pressure waves in an ultrasonic field
  • Produces viscous stresses altering cell membrane permeability to sodium and calcium ions (important in healing process)
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22
Q

Baseline muscle temperature

A
  • 36-37 C (98.6 F)
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23
Q

Mild heating

A
  • +1 C

- Accelerates metabolic rate in tissue

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24
Q

Moderate heating

A
  • +2-3 C
  • Decreased muscle spasm, pain, and chronic inflammation
  • Increased blood flow
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25
Q

Vigorous heating

A
    • 3-4 C
  • Decrease viscoelastic properties of collagen
  • Increased tissue elongation
  • Scar tissue reduction
26
Q

Continuous ultrasound indications

A
  • Acute and post-acute conditions (non-thermal)
  • Soft tissue healing and repair
  • Scar tissue
  • Joint contracture
  • Chronic inflammation
  • Increase extensibility of collagen
  • Decrease muscle spasms
  • Pain modulation
  • Increase blood flow
  • Increase protein synthesis
  • Tissue regeneration
  • Bone healing
  • Repair of nonunion fx
  • Decrease Inflammation (associated with myositis ossificans)
  • Myofascial trigger points
27
Q

Continuous ultrasound effects on the injury response process

A
  • Mode of application (continuous or pulsed)
  • Frequency of the sound
  • Size of the area treated
  • Vascularity and density of the target
28
Q

Acoustical streaming and cavitation

A
  • ↑ cell membrane permeability = changing the diffusion rate across the cell membrane
29
Q

Cellular responses to ultrasound

A
  • ↑ histamine release
  • ↑ intracellular calcium
  • Mast cell degranulation
  • ↑ rate of protein synthesis
30
Q

Thermal effects of continuous ultrasound

A
  • ↑ cell metabolism

- ↑ rate of inflammation

31
Q

Changes in cell membrane permeability with continuous ultrasound

A
  • Degranulation and the release of growth factors and platelets that stimulate fibroblast proliferation
  • Continuous ultrasound has been shown to positively influence macrophage activity and to increase the adhesion of leukocytes to the damaged endothelial cells
32
Q

Ultrasound stimulates cell division during

A
  • Proliferation phase
33
Q

Continuous ultrasound effects on blood and fluid dynamics

A
  • ↑ blood flow
    dilation of the blood vessels
  • ↑histamine release
34
Q

Continuous ultrasound effects on nerve conduction and pain control

A
  • ↑ nerve conduction velocity resulting from the thermal effects (cell membrane permeability to sodium ions is affected, altering the nerve’s electrical activity and elevating the pain threshold)
  • ↓ the activity of chemosensitive pain receptors
  • ↑ blood flow
  • ↑ capillary permeability
35
Q

Continuous ultrasound effects on muscle spasm

A
  • ↓ the mechanical and chemical triggers that continue the pain-spasm-pain cycle
  • Relaxation of muscle tension
  • ↑ blood flow
  • ↑ delivery of oxygen
  • Aiding in the elongation of muscle fibers
36
Q

Continuous ulstrasound effects on tissue elasticity

A
  • Heats collagen-rich tissues, especially tendon, ligament, fascia, and scar tissue
  • Vigorous heating
  • Not effective for large areas of muscle
37
Q

Vigorous heating with continuous ultrasound

A
  • 3 MHz, have an effective stretching time of just over 3 minutes after the end of the treatment
  • May be slightly longer when 1-MHz ultrasound is used
  • Not effective for large areas of muscle
38
Q

Continuous ultrasound effects on muscle and tendon healing

A
  • 1-MHz of continuous output ultrasound enhances the release of preformed fibroblasts
  • 3-MHz of continuous output ultrasound increases the cells’ ability to synthesize and secrete the building blocks of fibroblasts (localized to areas with a high collagen content, especially tendons and may be a more effective treatment for tendinopathies than phonophoresis)
39
Q

Continuous ultrasound effects on wound healing

A
  • Some superficial wounds have responded favorably to ultrasound application
  • Continuous ultrasound (100%) delivered at 1.5 W/cm2 x 5-minute treatment over a 1-week period can increase the breaking strength of incisional wounds
40
Q

Continuous ultrasound effects on fracture healing

A
  • Low-intensity pulsed ultrasound (LIPUS) applied in one 20-minute session per day has demonstrated an improved healing rate for acute and nonunion fractures
  • Results unclear for stress fractures
  • Less effective when applied late in the healing process
  • When applied early in the healing stage, cavitation and acoustical streaming increase the quality and strength of the bony callus
41
Q

Phonophoresis

A
  • Use of therapeutic ultrasound to assist in the diffusion of medication through the skin
  • Delivers medication over a larger area than an injection
  • Cavitation is believed to cause small openings in the stratum corneum and increase in pore size
42
Q

Phonophoresis preheating

A
  • Preheating the treatment area with a moist hot pack to increase local blood flow and kinetic energy can further enhance delivery of the medication into the tissues
43
Q

Commonly used medications with phonophoresis

A
  • Anti-inflammatory (cortisol, salicylates, dexamethasone, hydrocortisone)
  • Analgesic (lidocaine)
44
Q

Contraindications to therapeutic ultrasound

A
  • Impaired circulation
  • Ischemic areas
  • Areas having sensory deficit
  • Deep vein thrombosis or thrombophlebitis
  • Cancerous tumors
  • Over–fluid-filled cavities
  • Over implanted pacemaker
  • Pregnancy/menstruating women (over the pelvic area)
  • Active fractures or stress fractures
  • Metal or bony implants
  • Joint replacements
  • Caution over the vertebral column, nerve roots, or large nerve plexus
45
Q

Shortwave diathermy

A
  • Late 1800s
  • High-frequency alternating current flowing through a coil creates an electromagnetic field (EMF) that radiates away from the cable producing deep tissue heating
  • Larger treatment area (approximately the size of a cereal bowl)
46
Q

Indications for shortwave diathermy

A
  • Post-acute musculoskeletal injuries
  • Increase blood flow
  • Increase Vasodilation
  • Increase metabolism
  • Increase collagen extensibility
  • Increase nerve growth
  • Improved joint range of motion
  • Changes in some enzyme reactions
  • Muscle relaxation
  • Muscle guarding
  • Decrease pain threshold
  • Joint contractures
  • Myofascial trigger points
  • Decrease subacute and chronic pain
  • Re-absorption of hematoma
  • Decrease joint stiffness
47
Q

Continuous shortwave diathermy

A
  • ↑ subcutaneous tissue temperature

- Generally limited to chronic conditions

48
Q

Pulsed shortwave diathermy

A
  • Some acute and subacute conditions can be treated
  • Prevents tissue temperature from raising too fast or too high
  • Pulsed output can be used to produce thermal effects -not to be confuse “pulsed” with “nonthermal”
  • ↑the pulse frequency = the ↑ the amount of tissue heating
49
Q

Nonthermal effects of shortwave diathermy

A
  • Tissue healing
  • ↑ microvascular perfusion
  • Activation of fibroblast growth factors
  • Increased macrophage activity
50
Q

Shortwave diathermy nonthermal indications

A
  • Acute trauma

- Post-surgical treatment

51
Q

Thermal effects of shortwave diathermy

A
  • Can ↑ intramuscular temperatures in the level of 4 to 5C
  • Heating characteristics of SWD are similar to those of ultrasound, but because of the larger amount of tissue heated, the heat is retained three times longer
52
Q

Nonthermal effects of SWD on injury response

A
  • Alter the rate of diffusion across the cell membrane
53
Q

Thermal effects of SWD on injury response

A
  • ↑ the rate of cell metabolism
54
Q

Cellular level effects of SWD combined with increased blood flow

A
  • ↑ delivery and concentration of white blood cells and improved chondrocyte proliferation
  • Increased cell membrane permeability assists in the removal of cellular debris and metabolic toxins
55
Q

SWD and nerve conduction/pain control

A
  • Primary pain relief is associated with:
  • ↓ muscle spasm
  • Reduction of adhesions and contractures
  • ↑ blood flow
56
Q

SWD blood and fluid dynamics

A
  • Vasodilation
  • Increases blood flow
  • Capillary filtration
  • Capillary pressure
  • Oxygen perfusion
57
Q

SWD deep-heating characteristics

A
  • Increased blood flow
  • Increased fibroblastic activity
  • Increased collagen deposition
  • New capillary growth are stimulated deeper
58
Q

Tissue elongation with SWD is obtained by

A
  • Altering the viscoelastic properties of deep, collagen-rich fibrous tissues by increasing the temperature and applying an external force to elongate the tissues
59
Q

Wound healing and SWD

A
  • Pulsed SWD
  • ↑ white blood cell infiltration and ↑ rate of phagocytosis = more rapid healing time and ↓ need for pain medications
  • ↑ number and quality of collagen bundles
  • ↓ proportion of necrosed muscle fibers
60
Q

Contraindications and precautions of SWD

A
  • Acute inflammation
  • Ischemia
  • Hemorrhage
  • Sensory impairment
  • Pregnancy
  • Cardiac pacemaker (or other electronic devices)
  • Metal jewelry and implants
  • Deep vein thrombosis or thrombophlebitis
  • Cancerous tumors
  • Plastic implants
  • Bone cement
  • Precautions
  • Contact lenses (remove)
  • Unfused epiphyseal plates (with caution)
  • Moist dressings, adhesive tapes, skin creams (remove)

Physical Medicine (5 decks)

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