Quantifying the efficacy of first aid treatments for burn injuries using mathematical modelling and in vivo porcine experiments

Abstract

First aid treatment of burns reduces scarring and improves healing. We quantify the efficacy of first aid treatments using a mathematical model to describe data from a series of in vivo porcine experiments. We study burn injuries that are subject to various first aid treatments. The treatments vary in the temperature and duration. Calibrating the mathematical model to the experimental data provides estimates of the thermal diffusivity, the rate at which thermal energy is lost to the blood, and the heat transfer coefficient controlling the loss of thermal energy at the interface of the fat and muscle. Accidental burn injuries occur most frequently in children, and are a major cause of injury worldwide 1 . Burn injuries worsen after the initial insult 2 , as thermal energy and associated tissue destruction spreads into surrounding tissues. However, if first aid treatment is administered immediately at the scene or prior to qualified medical treatment, burn patients have improved healing outcomes 3 . Optimal first aid treatment conditions have been previously determined using standardised, controlled porcine burn models [4][5][6][7] . Porcine models are used because pig skin is anatomically and physiologically similar to human skin 8,9 , and pig skin responds to therapeutic agents in a similar way to human skin 10 . Recommended first aid treatment is the immediate administration of cool, running water for 20 minutes. This decreases tissue injury, increases the rate of wound healing and reduces scarring 4,6,7,11 . Ethically and morally, there is a limit to the number of different burn and treatment conditions that can be tested using live animals. Therefore, animal experiments cannot be used to examine all potential treatment temperatures and durations.In this work we use a porcine burn model, illustrated in Fig. 1, to study a series of standardised burns created by exposing the surface of the skin to a temperature of 92 °C for 15 seconds. The propagation of thermal energy through the skin is observed by measuring the temperature under the skin using a subdermal temperature probe. Using this approach we examine the effects of various first aid treatments by applying cooling water of various temperatures (0, 2 and 15 °C), for different durations (10, 20, 30 and 60 minutes). This data set provides a wealth of information about how thermal energy propagates through the skin, and clearly illustrates that different first aid treatments have a measurable effect. However, taken in isolation, even a high-quality reproducible experimental data set such as this does not provide sufficient information to quantify the efficacy of different first aid treatments as this requires more detailed spatial and temporal information about the propagation of thermal energy through the skin.To address this gap in our knowledge we examine a suite of experimental data describing the effect of various first aid treatment strategies using a mathematical model that describes the spatial and temporal distribution of thermal energy within the ski...

Parameterising continuum models of heat transfer in heterogeneous living skin using experimental data

“…The interface between the fat and the underlying muscle and bone is at x = l 2 > l 1 , and we have l 2 = 4.0 mm in this case. Our conceptual idealisation of the structure of the layered tissues is given in Figure 1(c) where the subdermal probe is placed at x = l 2 since experimental data reported by Cuttle involves placing the probe at the bottom of the fat layer [2,17]. A summary of the kind of experimental data reported by Cuttle is given in Figure 1(d).…”

Profile likelihood analysis for a stochastic model of diffusion in heterogeneous media

“…Our work is different since we focus on a stochastic process model and this avoids the need for specifying a separate noise model. This can be advantageous since the usual adoption of Gaussian noise models can be inappropriate for count data [23], density data [11] or length data [43], or any other data that are, by definition, non-negative. While the work here is motivated by experimental observations of diffusive transport in the context of heat transfer through a heterogeneous material, there are also many other applications, particularly in biophysics, that involve diffusive transport through layered structures where it is difficult to make observations at high spatial resolution [44,45].…”

“…While Andrews’ experiments focus on diffusive transport of thermal energy in layered biological material [21–24], a very similar experimental design could be used to measure the chemical diffusion of dissolved solutes through skin and other heterogeneous, layered media, with broad applications including cutaneous drug delivery [25] as well as the design of landfill liners for the storage of industrial waste [26,27].

Figure 1( a ) Histology image of porcine skin [23] highlighting the layered structure of the tissue, including the epidermis, dermis and fat layers, as indicated. ( b ) Experimental data from Andrews et al [21] showing the subdermal temperature response after a constant heat source at 50°C is placed on the surface of the skin.

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“…( a ) Histology image of porcine skin [23] highlighting the layered structure of the tissue, including the epidermis, dermis and fat layers, as indicated. ( b ) Experimental data from Andrews et al [21] showing the subdermal temperature response after a constant heat source at 50°C is placed on the surface of the skin.…”

Validating the relationship between burn temperature, duration of exposure and tissue injury severity for scald burns

“…This data has broad application to future heat transfer modelling investigations, such as those used to develop thermal injury prevention and treatment guidelines. For example, estimates for the thermal diffusivity and modelling established in this chapter have recently been used to inform a mathematical model examining changes in the temperature profile of the skin with the application of water as a first aid for burns (222). Importantly, while beyond the scope of this research project, the modelling presented in this chapter is vital for studies in this area investigating the more complex relationship between heat conduction and the severity of tissue damage.…”