Jwc ewma final indd

J O U R N A L  O F WO U N D  C A R E   Vo l   2 2 .  N o   1 .  E W M A   D o c u M E N t   2 0 1 3

Mechanismsofaction

While high-frequency ultrasound operates in the 

1–3MHz range and transmits the mechanical energy 

directly to the structures to which they are applied, 

low-frequency ultrasound (LFUS) works in the 

kilohertz (kHz) range and does not necessarily need 

direct contact with the tissue to exert its actions.

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The known mechanisms of action of LFUS 

vary according to the physical and biological 

modification that they induce at the cellular level, 

and occur more frequently in the kHz rather than 

in the MHz frequency range.

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Cavitation is the result of the formation of micro-

bubbles, which concentrate the acoustic energy 

and produce a shearing of cellular structures.

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This should act selectively, for example leading to 

removal of necrotic tissue, while healthy tissue is 

not influenced to the same degree. Microstreaming 

may be a consequence of cavitation, as it consists 

of a linear movement of macromolecules and ions 

around the stationary structure of the cells. The 

combination of cavitation and microstereaming 

can interfere with the cellular activity.

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A possible alternative mechanism of action, called 

frequency resonance, is related to the modification in 

the structure of proteins and the activation of signal 

transduction at nuclear level. This can lead to a range 

of effects at cellular level that impact wound healing, 

such as leucocyte adhesion, increased angiogenesis 

and increase of nitric oxide (NO) production.

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As in the case of NPWT, all these effects may 

indirectly promote the debridement of chronic 

lesions, shifting them towards the healing phase. 

The actions of LFUS are mediated by a medium 

of saline, which is vaporised by the US probe and 

transmits the mechanical energy to the wound bed.

Clinical studies have demonstrated an 

improvement in the healing process and positive 

effects on the microcirculation in many different 

models for treatment of chronic wounds.

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Limitations

Vaporisation of saline solution is probably the 

most relevant limitation of this technology. 

However, it can be managed by applying the 

same protection suggested for high-frequency 

ultrasound equipment. Another limitation is the 

great expertise necessary to effectively manage 

this technology. It is dependent on the user and 

requires the staff member using the equipment has 

specific technical knowledge about the device.

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Costeffectiveness

There is no clear information available about 

cost effectiveness of LFUS; however, it has been 

suggested that the office-based application of 

this technology may reduce costs related to 

hospitalisation of patients, as well as the number 

of surgical procedures required for debridement.

conclusions

The possibility of using new technologies in the 

debridement phase of wound healing is now a 

reality, with a complex structure and an ever-

increasing range of possible solutions relevant for 

any kind of acute and chronic wound typology.

The role of the clinician is to choose the best possible 

option for each case, taking into consideration the 

indications and technical characteristics, as well as 

the cost–benefit profile of the chosen option.

The limitations of this approach are primarily 

related to the relatively recent development of the 

technologies. This means that solid evidence has 

not yet been produced. This commits the scientists 

and clinicians working in wound healing and tissue 

repair to design and carry out studies challenging 

each technology within the indications for which 

they are suggested by manufacturers.

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