Low-Frequency Non-Contact Ultrasound and Pulsed Lavage

Question 1

What is the frequency range of high frequency US?

Answer 1

0.5-3.0 MHz

Question 2

What is the frequency range of low frequency US?

Answer 2

20-50 kHz

Question 3

What is the sound wave size of high frequency US?

Answer 3

Short–higher attenuation and absorption rates

Question 4

What is the sound wave size of low frequency US?

Answer 4

Long–lower attenuation and absorption rates

Question 5

What is the tissue penetration of high frequency US?

Answer 5

1. 0 MHz – 1-2 cubed cm

3. 0 MHz – 5 cubed cm

Question 6

What is the tissue penetration of low frequency US?

Answer 6

Noncontact 40 kHz – 3 cubed mm

Contact debridement devices depend on application technique

Question 7

What are the modes for high frequency US?

Answer 7

Continuous – tissue heating, 100% duty cycle

Pulsed – tissue repair, 20% duty cycle

Question 8

What are the modes for low frequency US?

Answer 8

Continuous and pulsed modes depending on the device

Heat dissipated by non-contact and by saline irrigation

Question 9

What is the application of high frequency US?

Answer 9

Direct contact with coupling medium

Question 10

What is the application of low frequency US?

Answer 10

Non-contact and contact devices depending on treatment goal

Question 11

What are the therapeutic uses of high frequency US?

Answer 11

Tissue healing, tissue repair, pain reduction

Question 12

What are the therapeutic uses of low frequency US?

Answer 12

Non-contact devices – tissue repair, wound cleansing, pain reduction

Contact devices – debridement

Question 13

What are the features of low frequency non-contact US?

Answer 13

PRIMARY METHOD OF US DELIVERY FOR WOUND MANAGEMENT (TREATMENT MODALITY)

This mist of sterile saline as a coupling medium to transfer US energy to tissues

Continuous energy that does not result in heating of tissues

• Low intensity therapeutic range
• Heat dissipating saline mist
• Noncontact delivery method

Produces higher levels of cavitation compared to HFUS
- Allows low frequency devices to deliver greater amounts of US energy to tissues during comparable treatment times

Question 14

How does low-frequency non-contact US work?

Answer 14

Uses low-frequency (40kHz) and low therapeutic intensities (0.1-0.5 W/squared cm

Tissue stimulation

Promotion of fibrinolysis

Removal of bacteria and exudate through cleansing

Active bacterial killing (damage to cell wall)

Proposed that LFUS may alter the genetic code of certain bacteria thus increasing antibiotic susceptibility and decreasing virulence

Question 15

What is Pulsed Lavage with Suction (PLWS) and the theory behind it?

Answer 15

Debridement and cleansing modality

Theory:

• Delivery of pulsed irrigation at controlled psi with suction of contaminated irrigation fluid
• Both positive and negative pressure

Question 16

What provides the POSITIVE PRESSURE with pulsed lavage with suction?

Answer 16

HYDROTHERAPY:

• With whirlpool, psi is not documented
• Psi too low—not effective for wound cleansing
• Psi too high—tissue can be damaged and bacteria pushed further into the wound
• Recommended psi between 4 and 15

Question 17

What provides the NEGATIVE PRESSURE with pulsed lavage with suction?

Answer 17

Suction forces stimulated granulation tissue proliferation and epithelization

Question 18

What are the BENEFITS of Pulsed Lavage with Suction?

Answer 18

Wound cleansing

Debridement of slough

Loosening of nonviable tissue

Reduction of surface bacteria

Increased local perfusion

Stimulation of granulation tissue through negative pressure

Question 19

What are the INDICATIONS of Pulsed Lavage with Suction?

Answer 19

Critically colonized wounds with decreased or stalled granulation tissue

Infected or necrotic wounds

Thick or mucous-like exudate

Undermining, tunneling or sinus tracts

Open amputation sites

Traumatic wounds with foreign debris

Stage 3 and 4 pressure ulcers

Question 20

What are the PRECAUTIONS associated with Pulsed Lavage with Suction?

Answer 20

Anticoagulants or active bleeding

Poorly visualized wound spaces

Near fistula or cavity linings

Near visible blood vessels

Over exposed tendon or bone

Near recent bypass grafts or recent surgical closures

Facial wounds

Near LVAD drives

Hypothermia with cool fluid irrigation

Question 21

What are the irrigation force parameters associated with PLWS?

Answer 21

4-6 psi for sensitive areas

• For initial treatment to gauge response
• Situations of anticoagulation therapy, fragile hemostasis, exposed structures, intense pain
• For tracts and tunnels, as low as 2 psi

8-9 psi to decrease bacterial load

9-15 psi for removal of debris in non-infected wounds

Question 22

What are the suction force parameters associated with PLWS?

Answer 22

60-80 mmHg for wounds that are painful or bleed easily

80-100 mmHg for removal of exudate and necrotic tissue

Question 23

What should the temperature of irrigation fluid be for PLWS?

Answer 23

37-38 degrees Celsius facilitates vasodilation and prevents wound tissue hypothermia

Question 24

What should the frequency and duration be for PLWS?

Answer 24

Wounds with infection, odor, or > 50% necrotic tissue
- 2x daily

For general cleansing and tissue stimulation
- Daily or scheduled every other or every third day

Should be discontinued after 1 week without improvement

Question 25

What are the PPE and environmental requirements for PLWS?

Answer 25

AEROSOLIZATION RISK
- PPE advised (hair cover, face shield or mask/goggles, waterproof gown, shoe covers, gloves)

INFECTION CONTROL

• Can reuse hand pieces on the same patient but needs to be thoroughly disinfected and stored in a sterile bag between uses
• Divertor tip (cone) should NOT be re-used, must be discarded

STERILE FIELD SURROUNDING THE WOUND SHOULD BE ESTABLISHED

EXTRA TOWELS TO ABSORB AND CATCH FLUIDS THAT SPILL DURING TREATMENT