Pneumatic Skin Flattening (PSF): A novel technology for marked pain reduction in hair removal with high energy density lasers and IPLs
Gary Lask MD (1), Malcolm Ke MD (2), David Friedman MD (3), Monica Elman MD (4), Nathalie Fournier MD (5)
(1) UCLA Medical School, Los Angeles, CA, USA, (2)Case Western Reserve University , Cleveland , Ohio, (3) LaseOhr Medical Centre , Jerusalem, Israel, (4) Beit Harofim, Holon, Israel, (5) CLDP, Calpier, France
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Abstract:
Background: Intense pulsed light aesthetic treatments such as hair removal or treatment of pigmented lesions are often very painful. Immediate acute pain is felt during each treatment pulse and can accumulate to an intolerable sensation after a few shots, resulting in the necessity either to use topical analgesic creams which have several limitations or else to considerably slow down the process and/or apply less efficient low energy densities. 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 with negative pressure: a) for the reduction or elimination of pain during hair removal with high energy density IPLs and pulsed lasers; b) for the reduction of post treatment erythema; c) for the enhancement of the efficacy of hair removal and the treatment of pigmented lesions. Materials and methods: We have removed hair from areas such as legs, backs, arms and armpits with a high energy (42 J/cm²) pulsed diode laser, Alexandrite lasers (26 J/cm2), Nd:YAG lasers (40 J/cm2), and IPLs (15-20 J/cm²). Room temperature skin moisturizer/ lubricant was applied to the skin before treatment. 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 200-800 mmHg range. We have compared the level of pain (I-V ) and the efficacy of hair removal on a total of over 60 treatment sites The results of the PSF assisted treatment sites were compared to the results on adjacent control areas, obtained without the application of vacuum. Post treatment erythema was also compared. Results: Pneumatic Skin Flattening (PSF) significantly reduces pain in all patients even when higher (+30%) treatment energy levels are applied. Post treatment 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 cream over a large area. Discussion: Pain inhibition by Pneumatic Skin Flattening (PSF) is attributed to the “gate theory”, namely the inhibition of pain transmission to the brain through the dorsal horn by activated pressure and tactile receptors in the skin. An important advantage of the PSF evacuation chamber is adaptable to most lasers and IPL. Introduction:
Intense pulsed light based aesthetic treatment, such as hair removal, is often very painful. The sensations of pain associated with treatment are: immediate acute pain and post treatment discomfort with erythema. The immediate acute pain is felt during each treatment pulse and can accumulate to an intolerable sensation after a few shot. Excessive heating generated by light scattered and absorbed by collagen and blood vessels in the skin induces redness and edema causing discomfort. The most common approach to the reduction of immediate acute pain is the application of topical anesthesia to the treated area of the skin. There are major well known disadvantages to analgesic creams. Skin chilling only helps to reduce pain to a certain degree. The alternative approach of reducing energy density is generally not recommended since it may compromise treatment efficacy. Materials and methods:
Patients: We have removed hair from 27 sites, on seven patients, with PSF using a vacuum chamber covered by a Sapphire window and from 18 adjacent control sites treated without PSF. The selected sites were on the back, leg, arm, chest, bikini line and armpit. Skin types ranged from 2 to 5. We also conducted several treatments of five entire backs and legs with PSF technology and examined hair reduction results. Equipment: Light sources: We have utilized lasers (Gentlelase (Candela), 755nm, 26 J/ cm2, 3 millisec) and LightSheer (Lumenis), 810 nm, 26-42 J/cm2, 30 millisec as well as IPLs (Harmony (Alma), 650-950 nm, 15-20 J/cm2 , 30-40 millisec) and PhotoSilk (Deka), 550 – 950 nm, 12 J/cm2, 12 millisec). The PSF vacuum chamber: The PSF (serenity, Inolase) comprised of a 26 X 52 mm lateral sizes, 7 mm height vacuum chamber and a pumping unit which pumps both compressible air and non- compressible moistening lotion from the treatment site. Negative pressure |
 
 
 
 
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of 600 mmHg was automatically attained within less than 0.5 sec following the placement of the hand piece on the treatment site. The vacuum chamber is covered with a transparent Sapphire window on which the skin is compressed as a result of the negative pressure (Figure 1). Blood is temporarily forced to the periphery around the treatment area resulting in a more transparent treatment site ( Figure 2). Essentially, any laser or IPL treatment hand piece held in the operator’s other hand could be conveniently placed on the vacuum chamber window. Once the negative pressure attained its preset level, the light treatment pulse was fired. This is automatically followed by a ventilation of the chamber, which takes place within less than 0.5 second, thereby releasing the vacuum to allow quick repositioning of the hand piece onto the next treatment spot. The rational for applying negative pressure is the well documented afferent inhibition of sensory nerves in the dorsal horn by activating tactile pressure nerves in a sufficiently large surrounding area (The gate theory – figure 3) (1) (2). The blood expulsion allows for more energy to reach the hair shaft and consequently is expected to improved efficacy of treatment. Moreover , the lack of pain further enables to increase energy and efficacy without sides effects. Pain evaluation: Acute pain evaluation was based on a modified McGill Pain Questionnaire, which is commonly used in pain evaluation (3). Pain was graded according to a five level scale: We also tested pain level on ten sites at milder vacuum levels (100400 mmHg). Results:
Hair removal efficacy: The hair removal efficacy of the PSF technique has been found identical to or better than the efficacy of regular non-vacuum hair removal at identical energy density levels and pulse durations on all patients. Figures 4, 5 and 6 compares hair removal efficacy with and without PSF with an IPL, a diode laser and an Alexandrite laser. Hair removal on the the PSF sites are more efficient Post treatment erythema: Post treatment erythema was considerably reduced and almost eliminated in all patients by applying the vacuum assisted pneumatic skin flattening technique ( Figure 7). Elimination of acute pain level: Figure 8 summarizes the statistical distribution of pain level with the PSF technique as compared to pain level in adjacent control sites without applying the PSF technique (27 PSF sites and, 19 non PSF control sites). The Chi-Square statistical test shows that PSF is significantly less painful than non-vacuum treatments (p< 0.06). Figure 9 shows the relation between pain level reduction and the vacuum level in the PSF chamber. We have found that 500-600 mmHg is the threshold for virtually painless treatments. Discussion and conclusions:
The application of over 500 mmHg negative pressure to the skin and its flattening against a transparent Sapphire window inhibits acute pain transmission and essentially ensures natural pain reduction in IPLs or laser based hair removal procedures. Moreover, higher energy densities may be utilized in treatment, thereby enabling efficient long-term results. Higher efficacy is obtained in many cases even at identical energy densities. A synergic benefit is the blood expulsion from the treatment area, which makes the skin appear more transparent. As a result, average skin temperature elevation is avoided and post treatment erythema is also eliminated. The pneumatic skin flattening technology is adaptable to any high energy density IPL or laser hair removal device. References:
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