BACKGROUND/AIMS: A new method for the in vivo characterization of the mechanical properties of skin has been developed. This comprises a suction chamber and an ultrasound device to measure both the vertical displacement of the skin's surface, and the skin's thickness. METHODS: A mathematical model of the mechanical behaviour of a taught elastic membrane is used to obtain a set of parameters intrinsic to the skin, such as Young's modulus (E) and the initial stress (sigma0), which reflect the stiffness and the natural tension of the skin, respectively. We also calculated an index of non-elasticity of the skin (unrestored energy ratio, UER), which takes into account the volume of tissue mobilized. It determines a ratio between the energy input to the skin and the energy it dissipates. These parameters were evaluated from the volar forearm of 10 normal male volunteers. RESULTS: The results were: 129+/-88 kPa for E, 13.5+/-5 kPa for sigma0, and 0.42+/-0.04 for UER; with reproducibilities of 9.5%, 12.4% and 6.4%, respectively. CONCLUSIONS: This new suction device was found useful for the study of the behaviour of the skin, and the device may be used for the evaluation of certain skin diseases and their therapy.

Objective. An algorithm for the detection of pulmonary arterial hypertension (PAH), based on the presence of dyspnea and the findings of Doppler echocardiographic evaluation of the velocity of tricuspid regurgitation (VTR) and right-sided heart catheterization (RHC), which was applied in a large multicenter systemic sclerosis (SSc) population, estimated the prevalence of PAH to be 7.85%. The aim of this observational study was to investigate the incidence of PAH and pulmonary hypertension (PH) during a 3-year followup of patients from the same cohort (the ItinérAIR-Sclérodermie Study).Methods. Patients with SSc and without evidence of PAH underwent evaluation for dyspnea and VTR at study entry and during subsequent visits. Patients in whom PAH was suspected because of a VTR of 2.8-3.0 meters/second and unexplained dyspnea or a VTR of >3.0 meters/second underwent RHC to confirm the diagnosis.Results. A total of 384 patients were followed up for a mean ؎ SD of 41.03 ؎ 5.66 months (median 40.92 months). At baseline, 86.7% of the patients were women, and the mean ؎ SD age of the patients was 53.1 ؎ 12.0 years. The mean ؎ SD duration of SSc at study entry was 8.7 ؎ 7.6 years. After RHC, PAH was diagnosed in 8 patients, postcapillary PH in 8 patients, and PH associated with severe pulmonary fibrosis in 2 patients. The incidence of PAH was estimated to be 0.61 cases per Supported by a research grant from Actelion Pharmaceuticals

We have investigated in vivo the change with age of various parameters that describe the physical properties of skin. The parameters were derived from pressure/displacement curves obtained by applying reduced pressure to a small area of skin and measuring the resulting displacement by 20 MHz scan echography. By fitting the pressure/displacement curves to a theoretical model, the following skin parameters were obtained: E, Young's modulus or stiffness (in Pascals); sigma(0), the initial stress (in Pascals); and the unrestored energy ratio (UER), an index related to cutaneous non-elasticity. These parameters, which are used in mechanics to define the intrinsic physical characteristics of materials, were measured for the first time on volar forearm skin of 206 male and female subjects, aged between 6 months and 90 years. The results showed that skin thickness increases until maturity and decreases for women over 50-60 years old, Young's modulus E increases linearly with age, and ageing is divided into two phases for natural stress, sigma(0) and the non-elasticity index UER. Natural stress sigma(0) increases until maturity and then rapidly decreases. The non-elasticity index decreases until puberty and steadily increases after puberty. This new procedure provides a simple quantitative assessment of the physical properties of the skin, revealing that the skin becomes thinner, stiffer, less tense and elastic with ageing.

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