Pneumatic skin flattening (PSF): a novel technology for marked pain reduction in hair removal with high energy density lasers and IPLs.

摘要

BACKGROUND: Intense pulsed light (IPL) aesthetic treatment, such as hair removal from large areas, is often very painful. The problems of pain and discomfort can be divided into two different phases: immediate acute pain and the long-term, milder, post-treatment discomfort also associated with erythema. The immediate acute pain is felt during each treatment pulse and can accumulate to an intolerable sensation after a few shots, resulting in the necessity of either using topical analgesic creams which have several limitations or else to considerably slow down the process and/or apply less efficient low-energy densities. The immediate pain is created by the stimulation of sensory nerves located near the basal layer of the epidermis and adjacent to the treated hair follicles. There is an interest in a technology which would significantly reduce acute pain and post-treatment erythema, without the necessity of lowering the energy density or speed of treatments. OBJECTIVES: To examine the advantages of pneumatic skin flattening (PSF) with negative pressure: (i) for the reduction or elimination of pain, without chilling the skin, during hair removal with high energy density IPLs and pulsed lasers; (ii) for the reduction of post-treatment erythema; and (iii) for the enhancement of hair removal. MATERIALS AND METHODS: We have removed hair from large areas such as legs and backs with a high-energy (42 J/cm2) pulsed diode laser and an IPL (15-20 J/cm2). Room temperature gel was applied to the skin before treatment. In all cases but one, skin was not chilled by external cooling devices. We utilized a vacuum chamber and a transparent sapphire window to generate deep negative pressure in the treatment site and flatten the skin against the window. The level of applied vacuum was in the 200-600 mmHg range. We have compared the level of pain (I-V according to a modified McGill Pain Questionnaire) and the efficacy of hair removal on a total of 40 treatment sites The results of the vacuum-assisted treatment sites were compared with the results on adjacent control areas, obtained without the application of vacuum. Post-treatment erythema was also compared. RESULTS AND CONCLUSIONS: PSF significantly reduces pain in all patients, even when higher (+30%) treatment energy levels are applied. Skin is well protected thermally by the conductive sapphire window. Post erythema and edema is considerably reduced, as well. Hair removal efficacy is preserved or enhanced. Treatment is faster and is uninterrupted by pain, without the necessity to apply topical anesthetic over a large area. Blood expulsion resulting from flattening the skin has also enabled the treatment of thin hair in light-skinned patients, using yellow and green wavelengths (540 nm cut-off filter) and short pulse durations with a higher efficacy than with the 650 nm cut-off filter.