Are iontophoresis and phono interchangeable?
No - no ionization takes place with ultrasound.
Describe Leduc's classic experiment:
To show that ionic medication could penetrate intact skin and produce local and systemic effects in animals he used two rabbits connected in the same current. One rabbit by a positive electrode soaked in a positive ion posion, the other connected to a negative electrode soaked in negative ion poison. Both rabbits died. When reversed neither rabbit was harmed.
Iontophoresis solutions indication and polarity: acetic acid
calcium deposits (-)
Iontophoresis solutions indication and polarity: dexamethasone sodium phosphate
inflammatory conditions (-)
Iontophoresis solutions indication and polarity: licocaine hydrochloride
skin anesthesia (+)
Iontophoresis solutions indication and polarity: potassium iodide
scar tissue (-)
Iontophoresis solutions indication and polarity: water
Iontophoresis solutions indication and polarity: Zinc oxide
ulcers, antiseptic (+)
Why are the effects of iontophoresis longer lasting than phonphoresis?
ions in superficial tissue with limited blood allows for time to be used, phono delivers it deeper where there is more vascularization.
Does increased drug concentration increase amount delivered?
Are there concerns with using direct current?
Yes, intact skin cannot tolerate current density >1 mA/cm2
Ion transfer depends on what factors?
1.) the concentration of ions in the solution 2. The current density of the active electrode 3. duration and current flow
List the polar effect on treated tissues produced by the anode (positive)
hyperpolarizes nerve fibers, repels bases, hardens tissues, stops hemorrhage, sedates/calms, reduces pain in acute situations
List the polar effect on treated tissues produced by the cathode (negative)
depolarizes nerve fibers, attracts bases (more damaging to skin), softens tissues, increases hemorrhage, stiumlates, reduces pain in chronic situations
Why do burns occur with ionto?
poor technique: poor skin-electrode interfaces, intensity too high, velcro straps too tight, electrodes too small/dry/size differential between anode and cathode, wrong polarity, DC current used
Where should iontophoretic electrodes be placed?
active electrode over treatment tissues, depressive electrode about 18 inches away to encourage a greater depth of penetration.
What are the advantages of ionto vs injection?
No carrier fluids, reduced risk of infections to noninvasive application, relatively painless, local delivery without GI side effects
Disadvantages of ionto?
numerous tx's may be required, limited depth penetration, costly electrodes, there are risks of polar effects and skin damage, setup and application are time consuming
How many serial iontophoretic treatments are safe?
one - six of dexamethasone
Does the magnitude current determine the depth of penetration?
No, diffusion vs magnitude of current determines depth penetration. Low magnitude ma be more effective than those at 10-30 mins.
Do buffered electrodes stabilize skin pH under the cathode?
Normal treatment conditions between 20-40 mA/min do not require it, but it is effective at 80 mA/min
What is the piezoelectric effect?
The crystal in the sound head will mechanically respond or deform when subjeced to AC by expanding and contracting at the same frequency at which the current changes polarity. material in front of the crystal compresses the material in front of it, when the crystal contracts it rarefies the material in front of it.
What is the beam nonuniformity ration (BNR)?
Variability of US wave produced by the machine. A low ratio means more uniform treatment. A higher ratio ie 8 W, means a 1W setting could vary from 1-8W during tx.
What is the effective radiating area (ERA) of a transducer?
About the size of ultrasound head, and treatment area should only be 2-3 x this size
What are the nonthermal and thermal ranges for US?
nonthermal .1-.3 W/cm2, thermal is anything greater than .3 W/cm2
Reported nonthermal effects of US?
increases cell permability, increases vascular permeability, increases blood flow in chronically ischemic tissue, stimulates collagen synthesis, stimulates phagocytosis, promotes tissue regeneration, breakes down scar tissue in acute injuries, kills bacteria and viruses in chronic situations
What are reported thermal effects of US?
heats collagen-rich tissues, increases tissue elasticity of collagen-rich tissue, increases blood flow, increases pain threshold, decreases muscle spasm, decreases pain and joint stiffness, causes a mild inflammatory response
How does ultrasound frequency relate to depth of penetration?
Increasing frequency will decrease depth; 1 MHz 2-5 cm depth, 3MHz 1-2 cm depth
Will tissue temp increases in human muscle vary between pulsed and continuous US application?
The same heating effect occurs between pulsed and constant
Is a metal implant an absolute contraindication for the use of ultrasound?
No, however caution should be exercised becuase ultrasound is contraindicated over plastic implants and joint cement, which are often components of a total joint replacement.