A model of measured percussive mechanical trauma and its effects on skin

In this study, the role of mechanical trauma to skin in industrial dermatitis is considered. The percussive component of mechanical trauma to skin is investigated by modelling it, using an oscillating device which can supply a range of percussive trauma doses. The instrument is electronically controlled, and contains sensors which monitor the force and displacement throughout each impact. From this information, a value proportional to the dose delivered to the skin is calculated and used, rather than the driving power of the percussor. The rate of dose is also controlled. In this study, doses were delivered at a frequency of 7 Hz. Eight volunteers were given regimens of percussive trauma at regular intervals over a 5-day period. Half the group received a dose of 4 mJ/cm2 per impact, the other half received double this dose. The skin response was evaluated using non-invasive measurements of transepidermal water loss, skin thickness, and erythema. The results demonstrate that erythema, skin thickness and transepidermal water loss are all increased after mechanical challenge--erythema and water loss by amounts dependent upon the trauma dose applied. The transepidermal water loss results indicate that for the subjects used in our study, there was a trauma threshold reached after a cumulative dose of greater than 250 J/cm2.