Minimally invasive cosmetic procedures, such as microdermabrasion, application of prescription topicals and non-ablative laser treatments are gaining in popularity. It seems more and more people are willing to achieve their cosmetic goal with less traumatic sequential treatments and virtually no down time. Common clinical goals seem to include collagen stimulation (for skin texture improvement and the reduction of fine lines), pigment reduction, and general skin rejuvenation from photoaging. Ultrasound and electrical stimulation can play a distinct role in the overall treatment of these problems.

Both ultrasound and electrical stimulation are excellent methods of increasing blood flow and have an extensive history in the treatment of wounds. Although ultrasound and electrical stimulation accomplish many of the same things, their mechanics are considerably different. It is imperative to fully understand their unique characteristics in order to safely utilize them in cosmetic applications.

Sound waves are mechanical pressure waves that are described in terms of their frequency. Audible sound has an approximate frequency range of 50 to 20,000 hertz. Ultrasound waves have frequencies greater than 20,000 cycles per second. Depth of penetration into tissue is determined by the frequency of the ultrasound. The lower the frequency, the greater the depth of penetration. The higher the frequency, the less the depth of penetration. An example of this is how apartment dwellers can hear musical deep bass notes through their walls and very little of the high frequency sounds. One Mhz (one million hertz) is the most common therapeutic ultrasound frequency. Physical therapists prefer this frequency because of its depth of penetration, which is about 3-5cm. Deeper penetration is required when treating shoulder and hip joints. Therefore, higher frequencies are more appropriate on the face because of thinner tissue. 2Mhz penetrates about 15mm. 3Mhz penetrates even less, but stands a greater chance of rapidly overheating superficial tissues.
 
When ultrasound enters the body it reacts in various ways. It is absorbed more readily by muscle, tendons and bone than by fat. Harder surfaces like bone will absorb and reflect ultrasound energy. All of these will play a role in the eventual total tissue temperature rise. Researchers have found that by raising the tissue temperature by 10 degrees C, the local metabolic rate will increase 3 to 4 times. This in turn dramatically increases Oxygen to the cells and the removal of waste products. Tissue can be heated to between 40 to 45 C without damage. Using a 2 MHz ultrasound at 1.5 watts per centimeter squared for 5 minutes will raise tissue temperature about 5 degrees C. Ultrasound intensity and time on tissue determines the amount of heat generated. Studies have shown that there also non-thermal benefits from ultrasound. These would be in the range of .5 watts per centimeter squared or less and or on pulsed.

Known clinical uses for ultrasound include:

Treatment of inflammation and edema reduction: Post trauma, either surgical or from a non-ablative laser causes degrees of inflammation. The goal is to reduce this swelling quickly to eliminate any further cellular damage. Low intensity ultrasound alters cell permeability and aides in the reabsorption of interstitial fluid. Heat generating settings should never be used, for heat would only exacerbate an already swollen situation.

Tissue Healing: Ultrasound has been shown to enhance tissue repair through increases in macrophages, fibroblasts, endothelial cells and collagen. Some feel that these stimulated repair mechanisms are from the heat generated by ultrasound, while others feel that the non-thermal effects of cellular micromassaging are the cause. The bottom line is that ultrasound has been proven to advance the healing process. Wounds of course represent the extreme, but stimulating photo damaged or sub-optimal aging skin will result in healthier more vibrant skin.

Phonophoresis: is the use of ultrasound to drive medications or topical products into the skin. The American Society for Aesthetic Plastic Surgery recently stated: "New skin care product formulations, used in conjunction with ultrasound, will allow for deeper penetration of topically applied rejuvenating agents into the skin, resulting in significantly improved aesthetic results." This is accomplished by the combined mechanical piston like effect of ultrasound and the altering of cell permeability. This process does not alter the chemical composition of the topical and is pleasant for the patient.
 
Increases extensibility of collagen tissue: Ultrasound used on higher intensities coupled with the stretching can improve the appearance and texture of scars.
 
Electrical Stimulation comes in many waveforms. The waveform described here is the one most accepted as an optimum stimulating waveform. This twin peaked, fast rise time, high voltage/micro amperage waveform most closely mimics the bodies endogenous bioelectric system. This enhancement of the natural electrical network has been shown to be valuable in a wound situation or where cells are not performing optimally. The goal with any form of stimulation is to achieve the proper depth in tissue with no harm to collateral tissue. This waveform is totally safe and comfortable for the patient.
 
Known clinical benefits of Electrical Stimulation include:

Improves blood flow and wound tensile strength: Improved blood flow is extremely important in most tissue related problems, whether the problem is an open wound or damaged cells. The mechanism of improved blood flow is related to electron flow and mild muscular contraction.

Stimulates protein and DNA synthesis in human fibroblasts: Electrical stimulation has been successfully used to treat decubitus ulcers for years. The U.S. Department of Health and Human Services stated that electrotherapy was the only adjunctive therapy they recommended for treating pressure ulcers. This was after evaluating hyperbaric oxygen, low-energy lasers, cytokine growth factors and a variety modalities and topicals.

Promotes migration of epithelial, fibroblast, neutrophil, and macrophage cells: These necessary factors of repair seem to be attracted to damaged tissue, and are required to contribute to granulation tissue formation and anti-inflammatory activities.

Edema reduction: Swelling reduction is important, especially in acute trauma. This is the reason that every major sports team uses E-Stim to dramatically reduce swelling in acute injuries. This same concept may be applied to post laser-resurfacing, liposuction etc.

Contraindications and precautions include not using any form of stimulation when tumors are present, either malignant or benign, cardiac pacemakers, over the eyes and pregnancy. Electrical stimulation may be felt stronger in sensitive teeth and where Botox injections have been given. Caution should also be used around the carotid area on the neck, with any form of stimulation.

The FDA considers all forms of ultrasound and electrical stimulation to be class II devices. This means that they may only be sold to and used under the guidance of a licensed physician. The FDA simply classifies devices that have the potential to create harm. It remains the responsibility of licensing boards of individual states to regulate their members.

There are important safety and reproducibility considerations with ultrasound equipment, just as with lasers or any other medical cosmetic device. The main goal in cosmetic ultrasound is to properly stimulate tissue to achieve optimum skin health. Choose an ultrasound with the proper frequency and safety features for the face. Standard off the shelf physical therapy devices with 1 MHz are too penetrating for cosmetic work. Accuracy at low and high power is critical, for sometimes your goal will be non-thermal and other times heat generation is required. An inaccurate device may afford results ranging from no results at all to the exact opposite of the desired result. An ultrasound that maintains your setting, regardless of the varying tissue impedances encountered is ideal. Another important issue is the equal distribution of ultrasound energy across the entire surface of the soundhead. If all the energy is being emitted from the center of the surface there is an extreme high power density, and once again you might be damaging cells rather that stimulating them. Think of the soundhead as an iron. You want a totally uniform deliver of heat. If all the heat came out of a small portion of the iron your results would be less than desirable. Ultrasounds are available in stand-alone units, as are electrical stimulators. There are also systems that combine both.

A successful skin care program will incorporate various tools to meet the patient's individual needs. Ultrasound and E-Stim offer solid clinical benefits that are cost effective. These systems not only offer their own specific benefits, but also work adjunctively with lasers and a wide variety of topical products. 

Michael Mosk President SoundSkin LLC 
20 years of medical sales experience: includes ultrasound, Zeiss microscopes, and every wavelength of laser. Lectured at physical therapy schools and rehabilitation centers on ultrasound and electrical stimulation as well as participated in numerous laser workshops. Was a participating member of product design team for ultrasound along with acoustic and electrical engineers. Helped initiate clinical studies using ultrasound and or high voltage electrical stimulation for treating TMJ dysfunction and decubitus ulcers. Designed and marketed an endoscope un conjunction with the Mayo Foundation.