Electrical Stimulation and Ultrasound Flashcards
What does electrical stimulation do?
Promotes wound healing by:
- Changing cell polarity
- Affecting cellular migration and function
- Increases blood flow
- Decreases edema
- Decreases bioburden
- Improves autolysis
What is the theory behind E-Stim?
Healthy, intact skin has a variable negative charge called the transepithelial potential difference
Break in the skin occurs–>
Influx of positively charged Na from the wound tissue interact with negatively charged Cl of adjacent intact skin–>
Creates a low level bioelectrical signal to the body that injury has occurred–>
Current of injury flows into the moist wound environment–>
Continues to signal that repair is necessary until a new epidermis is established
What are some things that can go wrong with the E-Stim theory?
Bioelectrical signal can be disrupted or halted by desiccation–> stalling wound healing
- Need to re-establish a moist wound healing environment
- Once established, can apply an external electrical current to mimic the normal one (Attacks key cells involved in tissue healing [electro-galvanotaxis] and reinitiates the healing process
What are the effects that E-Stim has at the tissue level?
Shown to have positive effects during all phases of tissue healing regardless of wound etiology
- Inflammation
- Proliferation
- Epithelialization
- Maturation and Remodeling
Ability to affect changes in cellular activity and migratory direction
What are the effects of E-Stim on the INFLAMMATORY PHASE?
Neutrophils and Macrophages
- Usually carry a negative charge
- Apply a electropositive field–> encourage increased numbers migrating to the wound
- Increased number of macrophages facilitates debridement
- In the case of infection, neutrophils are positively charged–> apply a negative charge to facilitate bacterial destruction and reduction of bioburden
What are the effects of E-Stim on the PROLIFERATIVE PHASE?
Fibroblasts
- Positively charged
- Apply a negative charge–> increase number and activity (Increased protein synthesis, collagen deposition, and overall faster wound contraction)
- Also encourages increased blood flow to the wound and periwound tissue by facilitating capillary density and inhibiting local vasoconstriction (effects may be enhanced by delivery in a warm environment)
What are the effects of E-Stim on the EPITHELIALIZATION PHASE?
Epithelial cells
- Negatively charged
- Apply positive charge to granulating wound–> increases migratory distance and speed of migration of epithelial cells across the wound surface
What are the effects of E-Stim on the REMODELING/MATURATION PHASE?
Apply positively charged electrical current–> repels like charged mast cells
- Shown to reduce scar hypertrophy
- Improve overall scar tensile strength
What are the indications for Electrical Stimulation?
Pressure injuries
Venous
Arterial
Traumatic
Surgical
Ischemia
Donor sites
Wound flaps
Burns
Clean wounds with
decreased or stalled healing
What are the two types of electrical current?
DIRECT CURRENT (DC) = often delivered as a pulsed current (PC), and is utilized for wound healing - Produces polarity change in the tissues
ALTERNATING CURRENT (AC) = NOT recommended for wound management - Produces a balanced, sinusoidal waveform which is neutral overall
What are the biophysical characteristics of DC and PC E-Stim?
Anode (positively charged electrode)
- Attracts negatively charged cells
Cathode (negatively charged electrode)
- Attracts positively charged cells
With PC, the flow of DC is interrupted (pulsed) at brief intervals with a finite “off” period between each pulse
Short pulse duration with biphasic current can make PC application more comfortable than DC application
- Prevents buildup of harmful ions under the electrodes
What are the biophysical characteristics of HIGH VOLTAGE PULSED CURRENT (HVPC)?
Monophasic
Delivers a short pulse duration (5-20 microseconds) and high voltage (75-100 V)
- Short duration and high peaked waveform decreases skin resistance so that current can penetrate into deep tissue
Makes ES delivery comfortable while decreasing the risk of skin damage from ion shifts
MOST SUPPORT IN PUBLISHED LITERATURE FOR USE IN TISSUE HEALING
What are the biophysical principles of LOW VOLTAGE PULSED CURRENT (LVPC)?
Monophasic or biphasic
- Monophasic: offers single selection of polarity
- Biphasic: offers choice of polarity or delivery of overall neutral charge
[Neutral charge delivery is thought to benefit wound healing through stimulation of local cutaneous nerves–> improving blood flow to the wounded area]
Delivers a longer pulse durations and lower voltage than high volt
- Short duration and high peaked waveform decreases skin resistance so that current can penetrate into deep tissue
What is direct electrode placement?
Primary treatment or “active” electrode with set polarity is placed directly in the wound bed
- Saline moistened gauze is commonly used
- Electrical charge is transferred from the lead wire to the gauze electrode via an alligator clip and aluminum foil
Dispersive electrode is needed to complete the circuit
What is indirect electrode placement?
2 active, same polarity electrodes (bipolar) placed on opposite ends of the wound
- Beneficial on small wounds that cannot accommodate one electrode
Dispersive electrode is placed the same as monopolar
Saline is placed in the wound bed and covered with an insulting dressing
What are the different E-Stim Parameters?
Voltage (Intensity)
Polarity
Pulse Duration and Frequency
Frequency and Duration
What are the characteristics of VOLTAGE (INTENSITY)?
Increased until patient feels a comfortable tingling under the electrodes
What are the characteristics of POLARITY?
Initial polarity is selected for either positive or negative charge depending on which specific cell is being targeted
What are the characteristics of PULSE DURATION AND FREQUENCY?
Duration set between 20-132 microseconds
Frequency set to 100-128 pps
What are the characteristics of FREQUENCY AND DURATION?
45-60 min/day for 5-7 days/week
What are the Precautions for E-Stim?
Children < 3 years old
Skin irritation or burns under electrodes
Areas of impaired sensation
Skin irritation/burns from ion shifts
What are the Contraindications for E-Stim?
Osteomyelitis
Presence of a cardiac pacemaker
Malignancy
Placement of electrodes
- Carotid sinus
- Phrenic nerve
- Overr topicals containing metals
What are the indications for Ultrasound?
Diabetic ulcers
Pressure injuries
Venous insufficiency
Traumatic
Debridement (contact LFUS)
Pain reduction (thermal and nonthermal application)
What are the characteristics of Ultrasound?
HIGH FREQUENCY vs LOW FREQUENCY
CAVITATION:
- Unstable cavitation causes preferential and rapid liquefaction and fragmentation (debridement) or necrotic tissues and microorganisms on the wound surface
ACOUSTIC STREAMING:
- Alter cell membrane permeability and second messenger activity–> increased protein synthesis, degranulation of mast cells, and increased production of growth factors by macrophages
END RESULT:
- The cell membrane and organelles become “excited” or upregulated, thereby increasing the activity levels of the entire cell
What are the characteristics of High Frequency US?
Rarely used in wound management
- BUT may be used to increase periwound tissue temperature–> local vasodilation
- May reduce pain (mechanism unclear)
When delivered in continuous mode at 1-3 MHz, cavitation and acoustic streaming occur with thermal effect of tissue heating
- Thermal heating due to cellular vibration and frictional forces
Potentially destructive
- Burns may occur in areas of insufficient blood flow to dissipate the heat
Pulsed mode is safer–> non-thermal effects
What are the characteristics of Low Frequency US CONTACT?
Used for selective debridement of nonviable tissue
Highly focused ultrasonic energy
Unstable cavitation
Continuous or pulsed depending on the device manufacturer
Normal saline used to irrigate debrided tissue and dissipate any heat that may be generated
Arobella, Sonoca 180, SonicOne
What are the characteristics of Low Frequency US NON-CONTACT?
Primary method for wound management
Produces higher levels cavitation compared to HFUS
40kHz with low therapeutic intensities (0.1-0.5 W/cm squared)
- Promotes wound healing through tissue stimulation, promotion of fibrinolysis, and removal of exudate and bacteria
- Active bacteria killing due to bacterial cell wall damage
MIST Therapy
What are the HFUS Parameters?
Based on phase of wound healing
Frequency based on depth of targeted tissue–lowest effective intensity advised
Pulsed mode (non-thermal) 20% duty cycle
- Frequency = 1 MHz for deeper tissues; 3 MHz for superficial
- Intensity = 0.3 W/cm for inflammation
0. 5 W/cm for proliferative phase
0. 5-1.0 W/cm for early phase of remodeling - Treatment frequency and duration can be daily, 5 minute applications during inflammatory and proliferative phases or 3x/week for 2 weeks during remodeling phase
What are the characteristics for DIRECT application of HFUS?
Superficial or superficial partial thickness wound
- Apply sterile hydrogel sheet dressing over open wound
- Apply US gel over hydrogel sheet
Deep partial thickness or full thickness wound
- Fill wound depth with hydrogel removing any air bubbles and ensure that there are no gaps
- Cover wound with sterile transparent film or hydrogel sheet
- Apply US gel on top of film or sheet
What are the characteristics of PERIWOUND application of HFUS?
Intact skin
- Apply US gel to intact periwound skin
- Can use hydrogel sheet to prevent direct contact if desired
Intact skin over tunnels or undermining
- Identify and irrigate all areas to be treated
- Fill all open areas with sterile hydrogel to decrease reflection
- Use US gel as the outer coupling medium
What are the precautions for US?
Same as for general US application
What are the contraindications for US?
Acute infection
Osteomyelitis
Active profuse bleeding
Severe arterial insufficiency (no thermal US)
Acute DVT
Necrotic wounds
Acute inflammation (no thermal US)
General US contraindications
