Skin friction blistering: computer model

A numerical analysis of skin-PPE interaction to prevent facial tissue injury

The use of close-fitting PPE is essential to prevent exposure to dispersed airborne matter, including the COVID-19 virus. The current pandemic has increased pressure on healthcare systems around the world, leading to medical professionals using high-grade PPE for prolonged durations, resulting in device-induced skin injuries. This study focuses on computationally improving the interaction between skin and PPE to reduce the likelihood of discomfort and tissue damage. A finite element model is developed to simulate the movement of PPE against the face during day-to-day tasks. Due to limited available data on skin characteristics and how these vary interpersonally between sexes, races and ages, the main objective of this study was to establish the effects and trends that mask modifications have on the resulting subsurface strain energy density distribution in the skin. These modifications include the material, geometric and interfacial properties. Overall, the results show that skin injury can be reduced by using softer mask materials, whilst friction against the skin should be minimised, e.g. through use of micro-textures, humidity control and topical creams. Furthermore, the contact area between the mask and skin should be maximised, whilst the use of soft materials with incompressible behaviour (e.g. many elastomers) should be avoided.

The enemy of the feet: blisters in ultraendurance runners

BACKGROUND

Blisters are the most common dermatologic problem in ultraendurance runners. Their incidence, localization, pain scores, and risk factors in field conditions are poorly understood.

METHODS

We conducted an observational field-based cohort study during the 5-day multistage 2010 and 2011 Al Andalus Ultimate Trail (219 km). Daily postrace data on blister frequency, localization, severity, and preventive measures from 50 ultramarathon runners were collected through the direct interview technique.

RESULTS

After 4 days of running (182 km), blisters occurred in 76% of the participants (P < .001 versus stage 1) compared with 34% after day 1, 54% after day 2, and 72% after day 3 (P < .001 versus stage 1). Most of the blisters formed on the toes (65%) (P < .001), followed by blisters on other locations of the foot: the ball of the foot (16%), heel (14%), and sole (5%). Blisters were more painful toward the end of the race, and those on the sole and heel tended to be the most painful, although this did not reach statistical significance. Prophylactic measures studied (type and fabric of socks; application of antiperspirants, talcum powder, or lubricant to feet; and prophylactic taping) did not show any reduction in blister rates. The only predictive marker for reduced blister incidence was previous ultramarathon experience in men (r = -0.44, P < .05).

CONCLUSIONS

Blisters are extremely common in multistage ultramarathon races. Race experience in male ultramarathon runners is associated with reduced blister rates.

Evaluation of dermatological consultations of patients treated in intensive care unit

BACKGROUND

Skin disorders which require treatment are a common development in patients treated in intensive care units (ICUs). There are very few prospective studies about skin complications in adult ICUs.

OBJECTIVE

The aim of this study is to evaluate skin disorders in ICU-treated adult patients who were consulted for dermatological problems.

METHODS

Eighty-two of 591 patients admitted to ICUs who were consulted for dermatological problems were included in the study. The correlation between skin complications and associated comorbidities, age, gender and ICU length of stay were analyzed.

RESULTS

Ninety dermatological complications were observed. Cutaneous drug reactions were significantly more frequent in female patients than males (p = 0.020). Candidal intertrigo was more frequent in diabetic patients than in nondiabetic patients (p = 0.042).

CONCLUSION

Patients in ICUs may develop various skin disorders that need to be evaluated by dermatological consultations. Clinical features of the patients, especially gender and comorbidities, may predispose skin complications.

How to identify water from thickener aqueous solutions by touch

Water detection is one of the most crucial psychological processes for many animals. However, nobody knows the perception mechanism of water through our tactile sense. In the present study, we found that a characteristic frictional stimulus with large acceleration is one of the cues to differentiate water from water contaminated with thickener. When subjects applied small amounts of water to a glass plate, strong stick-slip phenomena with a friction force of 0.46 ± 0.30 N and a vertical force of 0.57 ± 0.36 N were observed at the skin surface, as shown in previous studies. Surprisingly, periodic shears with acceleration seven times greater than gravitational acceleration occurred during the application process. Finite-element analyses predicted that these strong stimuli could activate tactile receptors: Meissner's corpuscle and Pacinians. When such stimuli were applied to the fingertips by an ultrasonic vibrator, a water-like tactile texture was perceived by some subjects, even though no liquid was present between the fingertip and the vibrator surface. These findings could potentially be applied in the following areas: materials science, information technology, medical treatment and entertainment.

Closed incision management with negative pressure wound therapy (CIM): biomechanics

A novel closed incision management with negative pressure wound therapy (CIM) has been developed for convenient use with closed incisions that has the potential to be beneficial for patients at risk for postoperative complications. Incisions are typically under lateral tension. This study explored the biomechanical mechanisms by which integrity of the incisional closure is enhanced by CIM. CIM was hypothesized to affect local stresses around closed incisions in a beneficial manner. Finite element analyses (FEA) indicated that application of CIM decreased the lateral stresses ~50% around the incision and changed the direction of the stresses to a distribution that is typical of intact tissue. Bench evaluations corroborated findings that CIM significantly increased the force required to disrupt the closed incision by ~50% as compared with closure alone. In conclusion, using 2 FEAs and bench modeling, CIM was shown to reduce and normalize tissue stresses and bolster appositional forces at the incision.

Plantar shear stress distribution in athletic individuals with frictional foot blisters

BACKGROUND

Foot blisters are common and painful nuisances in competitive sports and in military service. The pathogenesis of the problem is related to excessive frictional forces experienced on or under the foot. The incidence of foot blisters in marathon runners can reach 39%. Similarly, up to 42% of cadets in Reserve Officers' Training Corps camps might be prone to foot blisters. Although the problem usually disappears within 5 days, a single blister might be a major problem in competitive sports or in a wilderness setting. Military training and combat effectiveness might also be compromised by foot blisters. This study sought to reveal the distribution of plantar shear forces in athletic individuals and its relevance to foot blisters.

METHODS

Three groups of 11 participants each were studied: blister, adult control, and pediatric control. A custom-built shear and pressure platform was used to collect plantar pressure and shear data while the participants walked over the device. Data were analyzed with repeated-measures analysis of variance.

RESULTS

The blister group had significantly increased pressure and shear stress magnitudes compared with the other groups, although no significant group-site interaction was found. The shear-time integral values were increased approximately 50% at specific sites of the athletic feet, suggesting that contact time may play a role in blister formation.

CONCLUSIONS

The biomechanical interaction on the plantar surface of a blister-prone person is different from that of individuals who are less prone to the problem.

Friction coefficients in a longitudinal direction between the finger pad and selected materials for different normal forces and curvatures

This study investigated the effect of object curvature, normal force and material on skin friction coefficient. Twelve subjects slid their middle fingertip pad against a test object with small (11 mm), medium (18, 21 mm) or large (flat object) radii of curvature, while maintaining a normal force of 1, 10 or 20 N. Tested materials were aluminium and four rubber hoses. The average friction coefficient was 0.6 for aluminium and 0.9 for the rubber hoses. As normal force increased from 1 to 20 N, the average friction coefficient decreased 46%. Friction coefficient did not vary significantly with object curvature. The citation of friction coefficient data requires careful attention to normal force levels with which they are measured, but not so much to object curvature between 11 mm and infinity. This study provides skin friction coefficient data that are needed for design of objects that are manipulated with the hands. The investigation of the effect of object curvature on skin friction coefficient has important implications to ergonomics practices as many objects handled in everyday activities have curved surfaces.