Fibroblast migration and collagen deposition during dermal wound healing: mathematical modelling and clinical implications,

The extent to which collagen alignment occurs during dermal wound healing determines the severity of scar tissue formation. We have modelled this using a multiscale approach, in which extracellular materials, for example collagen and fibrin, are modelled as continua, while fibroblasts are considered as discrete units. Within this model framework, we have explored the effects that different parameters have on the alignment process, and we have used the model to investigate how manipulation of transforming growth factor-β levels can reduce scar tissue formation. We briefly review this body of work, then extend the modelling framework to investigate the role played by leucocyte signalling in wound repair. To this end, fibroblast migration and collagen deposition within both the wound region and healthy peripheral tissue are considered. Trajectories of individual fibroblasts are determined as they migrate towards the wound region under the combined influence of collagen/fibrin alignment and gradients in a paracrine chemoattractant produced by leucocytes. The effects of a number of different physiological and cellular parameters upon the collagen alignment and repair integrity are assessed. These parameters include fibroblast concentration, cellular speed, fibroblast sensitivity to chemoattractant concentration and chemoattractant diffusion coefficient. Our results show that chemoattractant gradients lead to increased collagen alignment at the interface between the wound and the healthy tissue. Results show that there is a trade-off between wound integrity and the degree of scarring. The former is found to be optimized under conditions of a large chemoattractant diffusion coefficient, while the latter can be minimized when repair takes place in the presence of a competitive inhibitor to chemoattractants

Impact of observing hand hygiene in practice and research: a methodological reconsideration

The purpose of hand hygiene is to break the chain of healthcare-associated infection. In many countries hand hygiene is regularly audited as part of quality assurance based on recommendations from the World Health Organization. Direct observation is the recommended audit method but is associated with disadvantages, including potential for being observed to alter usual behaviour. The Hawthorne effect in relation to hand hygiene is analogous with productivity improvement by increasing the frequency with which hand hygiene is undertaken. Unobtrusive and/or frequent observation to accustom staff to the presence of observers is considered an acceptable way of reducing the Hawthorne effect, but few publications have discussed how to implement these techniques or examine their effectiveness. There is evidence that awareness of being watched can disrupt the usual behaviour of individuals in complex and unpredictable ways other than simple productivity effect. In the presence of auditors, health workers might defer or avoid activities that require hand hygiene, but these issues are not addressed in guidelines for practice or research studies. This oversight has implications for the validity of hand hygiene audit findings. Measuring hand hygiene product use overcomes avoidance tactics. It is cheaper and generates data continuously to assess the compliance of all clinicians without disrupting patient care. Disadvantages are the risk of overestimating uptake through spillage, wastage, or use by visitors and non-clinical staff entering patient care areas. Electronic devices may overcome the Hawthorne and avoidance effects but are costly and are not widely used outside research studies