Thermal Conditions which Cause Skin Burns

Coated Cast Saw Blades Decrease Blade Temperature During Cast Removal

BACKGROUND

Thermal injuries can occur during cast removal with an oscillating saw. The purpose of this study is to describe the effect of blade material, blade wear, and cast material on blade temperature.

METHODS

Short arm plaster and fiberglass casts were cured overnight and bivalved with either new or worn stainless-steel or tungsten-disulfide coated blades. Blade use was defined as removing 1 short arm cast. Blades used to remove more than 20 casts were defined as worn. Ten trials were performed with each combination of blade material, blade wear, and cast material, except for the combination of fiberglass and a worn stainless-steel blade due to complete erosion of cutting teeth. Thirty casts were removed with stainless-steel blades, and 40 casts were removed with coated blades. Blade temperature was measured continuously at 5 Hz using a T-type thermocouple and microcontroller board. A Mann-Whitney U test was used to compare the mean maximum temperature between groups.

RESULTS

For plaster casts, new and worn stainless-steel blades produced mean maximum temperatures of 51.4°C and 63.7°C ( P =0.003), respectively. New stainless-steel blades produced significantly higher mean maximum temperatures on fiberglass casts than plaster casts (95.9°C vs. 51.4°C, P <.001). For plaster casts, new and worn coated blades produced mean maximum temperatures of 56.9°C and 53.8°C ( P =0.347). For fiberglass casts, new and worn coated blades produced mean maximum temperatures of 76.6°C and 77.7°C ( P =0.653). As with new stainless-steel blades, new coated blades produced significantly higher mean maximum temperatures on fiberglass than plaster (76.6°C vs. 56.9°C, P <0.001). Mean maximum temperatures between new stainless-steel and coated blades during removal of plaster casts were 51.4°C and 56.9°C ( P =0.131), respectively. However, new coated blades demonstrated significantly lower mean maximum temperatures during fiberglass cast removal compared to new stainless-steel blades (76.6°C vs. 95.9°C, P =0.016).

CONCLUSIONS

Coated blades outperformed stainless-steel in nearly all combinations. We recommend limited use of stainless-steel blades to minimize blade temperatures during cast removal.

CLINICAL RELEVANCE

Appropriate selection of blade material and monitoring blade wear minimizes blade temperature during cast removal.

Effects of Temperature and Humidity on Energy Dissipation between Human Corneocytes and Nanoasperity Sliding Contacts

Human haptic perception relies on the ability of sensory receptors underneath the skin corneocyte layer to sense external load, where adhesion and friction play an essential role in nanoscale solid-solid contact. Energy dissipation present at the surface interface due to the change of separation distance during sliding contact was uncovered, but the energy dissipation of human finger skin cell-nanoprobe contact under humidity and temperature conditions has not been investigated yet. In this paper, the energy dissipation of skin corneocyte-nanoprobe interface under variation of both humidity, 0.05-80%RH, and temperature ranging from 25 to 40 °C is directly measured by atomic force microscopy (AFM). Analytical models of dissipation energy for this nanomaterial interface mechanism are developed, and the results are compared to the measured values. AFM measurements of dissipation energy reveal that the amount of dissipated energy caused by water meniscus stretching monotonically increases with humidity and temperature, resulting in adhesion and friction decreases. The purposed analytical model represents that dissipation energy trend.

Skin-Integrated Wireless Odor Message Delivery Electronics for the Deaf-blind

Deaf-blindness limits daily human activities, especially interactive modes of audio and visual perception. Although the developed standards have been verified as alternative communication methods, they are uncommon to the nondisabled due to the complicated learning process and inefficiency in terms of communicating distance and throughput. Therefore, the development of communication techniques employing innate sensory abilities including olfaction related to the cerebral limbic system processing emotions, memories, and recognition has been suggested for reducing the training level and increasing communication efficiency. Here, a skin-integrated and wireless olfactory interface system exploiting arrays of miniaturized odor generators (OGs) based on melting/solidifying odorous wax to release smell is introduced for establishing an advanced communication system between deaf-blind and non-deaf-blind. By optimizing the structure design of the OGs, each OG device is as small as 0.24 cm3 (length × width × height of 11 mm × 10 mm × 2.2 mm), enabling integration of up to 8 OGs on the epidermis between nose and lip for direct and rapid olfactory drive with a weight of only 24.56 g. By generating single or mixed odors, different linked messages could be delivered to a user within a short period in a wireless and programmable way. By adopting the olfactory interface message delivery system, the recognition rates for the messages have been improved 1.5 times that of the touch-based method, while the response times were immensely decreased 4 times. Thus, the presented wearable olfactory interface system exhibits great potential as an alternative message delivery method for the deaf-blind.

Balancing Acute and Chronic Occupational Risks: The Use of Nitrile Butadiene Rubber Undergloves by Firefighters to Reduce Exposure to Toxic Contaminants

Firefighters are exposed via multi-route exposure to a multitude of chemicals (PAHs, VOCs, flame retardants, dioxins, etc.) that may cause acute and long-term health effects. The dermal absorption of contaminants is a major contributor to the overall exposure and can be reduced by wearing appropriate personal protective equipment. As leather firefighters' gloves cannot be decontaminated regularly by wet cleaning, many Belgian firefighters wear supplementary undergloves made of nitrile butadiene rubber (NBR) to protect against the accumulation of toxicants. However, the safety of this practice has been questioned. In this commentary, the current practice and risks are outlined for the first time, assessed by an interdisciplinary working group of the Belgian Superior Health Council. As NBR sticks to the skin more at high temperatures, the contact time on removal will be prolonged, posing an additional risk for deeper burns. However, based on the physicochemical properties of NBR and the existing experience of firefighters and burn centers, it is estimated that such incidents occur relatively rarely in practice. On the other hand, the risk of repeated exposure to contaminated gloves if no undergloves are worn is unacceptable. Despite the slightly increased risk for deeper burns, it is concluded that wearing disposable NBR gloves under regular firefighters' gloves is an appropriate and effective preventive measure against toxic contamination. The nitrile butadiene rubber must always be fully covered to avoid any contact with the heat.

Trial of a Trivial Quantitative Heat-Pain Stimulus for Detecting Severe Loss of Nociception

BACKGROUND

Loss of nociception (LON) at the feet of persons with diabetes mellitus develops gradually over years and remains asymptomatic until the first painless diabetic foot ulceration (DFU). Severe LON with pain insensitivity can be diagnosed with a mechanical (pinprick) pain stimulus of 512-mN force. A comparable "suprathreshold" heat-pain stimulus may have the same potential.

OBJECTIVE

A six-second, 51°C heat-pain stimulus delivered on a 38.5-mm² spot by a commercial medical device (bite away®, to treat insect bites) was explored in a prospective cross-sectional diagnostic accuracy study to detect DFU-related LON.

METHODS

Seventy-two participants were studied: 12 with and 30 without diabetic neuropathy according to the conventional criteria, and 30 patients with a history of painless DFU (indicative of end-stage LON, reference standard). The feet were stimulated at the plantar and dorsal sides. A palmar surface was stimulated for control purposes. Participants scored stimulated pain intensity 0 to 10 on a numerical rating scale.

RESULTS

At hands, pain intensity was rated six on average by all participants. Persons without neuropathy scored 7 (0-10), median (range), at the plantar side and 8.5 (2-10) at the dorsal side of the foot, while those with DFU scored 0 (0-8) and 0 (0-10), respectively. A pain response of 0 at the foot dorsum detected DFU-related LON with a sensitivity of 65% (specificity, 100%; positive and negative predictive values, 100% and 96%, respectively).

CONCLUSIONS

Due to its high specificity, the test seems advantageous for diagnostic purposes, complementary to current screening tests.

Carbon Dioxide Sensing-Biomedical Applications to Human Subjects

Carbon dioxide (CO2) monitoring in human subjects is of crucial importance in medical practice. Transcutaneous monitors based on the Stow-Severinghaus electrode make a good alternative to the painful and risky arterial "blood gases" sampling. Yet, such monitors are not only expensive, but also bulky and continuously drifting, requiring frequent recalibrations by trained medical staff. Aiming at finding alternatives, the full panel of CO2 measurement techniques is thoroughly reviewed. The physicochemical working principle of each sensing technique is given, as well as some typical merit criteria, advantages, and drawbacks. An overview of the main CO2 monitoring methods and sites routinely used in clinical practice is also provided, revealing their constraints and specificities. The reviewed CO2 sensing techniques are then evaluated in view of the latter clinical constraints and transcutaneous sensing coupled to a dye-based fluorescence CO2 sensing seems to offer the best potential for the development of a future non-invasive clinical CO2 monitor.

Establishing Safety Parameters for Orthopaedic Cast Saw Blade Usage

BACKGROUND

The incidence of injuries from cast saws during cast removal ranges from 0.12% to 4.3%. With 1 second or less of exposure time, a temperature of 65°C can cause partial thickness burns. Despite numerous studies that recommend avoiding the use of a dull blade, there is no objective measure of what defines dullness.

METHODS

Plaster and fiberglass casts were collected and measured after removal from patients in the clinic. A series of slabs were constructed based on these measurements. To simulate our emergency department setting, a Stryker 940 cast saw without an attached vacuum was used to split plaster slabs. A thermocouple was used to directly measure the 940-23 ion-nitride saw blade temperature after each use. To simulate our orthopaedic clinic setting, a Stryker 940 cast saw with an attached vacuum was used to split fiberglass and plaster slabs. Three blades were tested in each setting, bivalving 50 slabs each.

RESULTS

For the plaster slabs split without a vacuum, average blade temperature of the 3 blades reached 65°C on the 42nd cast. However, the individual blades exceeded 65°C on the 33rd, 31st, and 38th casts, respectively. For the fiberglass and plaster slabs split with a vacuum, average blade temperature reached a maximum of 57.5°C in the first 50 trials. Extrapolating from this data, the blade is predicted to exceed 65°C on the 104th cast.

CONCLUSIONS

When a Stryker 940 cast saw without vacuum is used to cut plaster casts, the ion-nitride blade should be changed frequently, at minimum after 60 casts have been split, or 30 casts have been bivalved. When a Stryker 940 cast saw with vacuum is used to remove fiberglass and plaster casts, the ion-nitride blade should be changed after removing 103 casts. A cast saw with an attached vacuum should be used whenever possible to minimize the risk of burning patients.

CLINICAL RELEVANCE

Determine how often a cast saw blade should be changed to minimize risk of burning patients.

The Efficacy of Silver-Based Electrospun Antimicrobial Dressing in Accelerating the Regeneration of Partial Thickness Burn Wounds Using a Porcine Model

(1) Background: Wounds with damages to the subcutaneous are difficult to regenerate because of the tissue damages and complications such as bacterial infection. (2) Methods: In this study, we created burn wounds on pigs and investigated the efficacy of three biomaterials: polycaprolactone-gelatin-silver membrane (PCLGelAg) and two commercial burn dressings, Aquacel^® Ag and UrgoTul^TM silver sulfadiazine. In vitro long-term antibacterial property and in vivo wound healing performance were investigated. Agar diffusion assays were employed to evaluate bacterial inhibition at different time intervals. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time-kill assays were used to compare antibacterial strength among samples. Second-degree burn wounds in the pig model were designed to evaluate the efficiency of all dressings in supporting the wound healing process. (3) Results: The results showed that PCLGelAg membrane was the most effective in killing both Gram-positive and Gram-negative bacteria bacteria with the lowest MBC value. All three dressings (PCLGelAg, Aquacel, and UrgoTul) exhibited bactericidal effect during the first 24 h, supported wound healing as well as prevented infection and inflammation. (4) Conclusions: The results suggest that the PCLGelAg membrane is a practical solution for the treatment of severe burn injury and other infection-related skin complications.

Quantitative Photothermal Characterization with Bioprinted 3D Complex Tissue Constructs for Early-Stage Breast Cancer Therapy Using Gold Nanorods

Plasmonic photothermal therapy (PPTT) using gold nanoparticles (AuNPs) has shown great potential for use in selective tumor treatment, because the AuNPs can generate destructive heat preferentially upon irradiation. However, PPTT using AuNPs has not been added to practice, owing to insufficient heating methods and tissue temperature measurement techniques, leading to unreliable and inaccurate treatments. Because the photothermal properties of AuNPs vary with laser power, particle optical density, and tissue depth, the accurate prediction of heat generation is indispensable for clinical treatment. In this report, bioprinted 3D complex tissue constructs comprising processed gel obtained from porcine skin and human decellularized adipose tissue are presented for characterization of the photothermal properties of gold nanorods (AuNRs) having an aspect ratio of 3.7 irradiated by a near-infrared laser. Moreover, an analytical function is suggested for achieving PPTT that can cause thermal damage selectively on early-stage human breast cancer by regulating the heat generation of the AuNRs in the tissue.

Standards in Biologic Lesions: Cutaneous Thermal Injury and Inhalation Injury Working Group 2018 Meeting Proceedings

On August 27 and 28, 2018, the American Burn Association, in conjunction with Underwriters Laboratories, convened a group of experts on burn and inhalation injury in Washington, DC. The goal of the meeting was to identify and discuss the existing knowledge, data, and modeling gaps related to understanding cutaneous thermal injury and inhalation injury due to exposure from a fire environment, and in addition, address two more areas proposed by the American Burn Association Research Committee that are critical to burn care but may have current translational research gaps (inflammatory response and hypermetabolic response). Representatives from the Underwriters Laboratories Firefighter Safety Research Institute and the Bureau of Alcohol, Tobacco, Firearms and Explosives Fire Research Laboratory presented the state of the science in their fields, highlighting areas that required further investigation and guidance from the burn community. Four areas were discussed by the full 24 participant group and in smaller groups: Basic and Translational Understanding of Inhalation Injury, Thermal Contact and Resulting Injury, Systemic Inflammatory Response and Resuscitation, and Hypermetabolic Response and Healing. A primary finding was the need for validating historic models to develop a set of reliable data on contact time and temperature and resulting injury. The working groups identified common areas of focus across each subtopic, including gaining an understanding of individual response to injury that would allow for precision medicine approaches. Predisposed phenotype in response to insult, the effects of age and sex, and the role of microbiomes could all be studied by employing multi-omic (systems biology) approaches.

Contact Burns From Central Heating Radiators in Adults-An Increasing Problem in an Aging Population

The primary method of heating residential dwellings in the developed world is through central heating radiators. These appliances are a major risk factor for contact burns, especially in individuals at the extremes of age. This article presents our findings of radiator contact burns in adults treated at a regional burns service during a 6-year period. We identified a total of 116 patients and 60% were male. The mean age was 58 (range 16-97), 71% had at least one comorbidity, with a mean of 1.88 comorbidities for each patient (range 0-8). The mean TBSA was 1.7% (range 0.1-8). Thirty-three patients (26%) required at least one operation with the average number of procedures being 1.45 (range 1-4). The mean length of stay was 16 days (range 0-98) compared to 7.5 days for all admitted patients across the same period. Four patients died within 30 days of their injury, 7 within 90 days, and 16 had died within 1 year of their injury. There have been previous smaller studies looking at contact burns from radiators in both adult and pediatric populations, demonstrating a bi-modal distribution at the extremes of age. This study is the largest of its kind looking specifically at an adult population and demonstrates that these injuries tend to occur in a population with a number of other comorbidities. These patients often required prolonged hospital care.

Enhanced Follicular Delivery of Finasteride to Human Scalp Skin Using Heat and Chemical Penetration Enhancers

PURPOSE

The aim of this work was to evaluate whether improved topical delivery of finasteride, focussed to the hair follicles of human scalp skin could be achieved with application of short durations of heat and use of specific chemical penetration enhancers.

METHODS

Franz cell experiments with human scalp skin were performed with a range of chemical penetration enhancers at 32°C and 45°C to simulate normal and heated conditions. Selected chemical penetration enhancers were taken forward for finite dose Franz cell studies which examined the effect of heat produced by a prototype external heating system that supplied either 20 or 30 min of additional heat over both a 24 h and a 1 h time period.

RESULTS

Short durations of externally applied heat significantly increased finasteride penetration into human scalp skin after 24 h. Analysis of drug distribution in the skin after 1 h and 24 h indicated that both heat and chemical penetration enhancer selection influenced drug delivery to the hair follicles.

CONCLUSION

The use of short durations of heat in combination with specific chemical penetration enhancers was able to increase the delivery of finasteride to human scalp skin and provide focussed drug delivery to the hair follicles.

A new experimental methodology for assessing adhesive properties shows that Neandertals used the most suitable material available

The use of adhesives for hafting stone tools at least 191 ka was a major technological development. Stone tools could be more securely attached to handles, thus improving their efficiency and practicality. To produce functional adhesives required forethought and planning, as well as expertise and knowledge of the resources available in the landscape. This makes adhesives important in discussions about Neandertal and early modern human technological and mental capabilities. However, we currently know very little about how these early adhesive materials behaved under different circumstances, or why certain materials were used and others were not. Here we present the results of controlled laboratory bulk property tests (hardness, rheology and thermogravimetric analysis) on replica Paleolithic adhesives. We conclude that birch tar is more versatile, has better working properties, and is more reusable than pine resin, the most likely alternative material. Neandertals may therefore have invested more time and resources to produce birch tar because it was the best material available, both functionally and economically, throughout the majority of Europe during the Middle to Late Pleistocene. Our results further demonstrate that Neandertals had high levels of technological expertise and knowledge of the natural resources available to them in their environment.

Anti-Inflammatory Effects of Cold Thermal Therapy on Allergic Skin Inflammation Induced by Trimellitic Anhydride in BALB/c Mice

Cold and hot thermal therapies are widely used as a traditional therapy in many cultures and are often prescribed in the treatment of various musculoskeletal and neurological conditions which present themselves to primary care physicians. However, there are no reports that investigated either the effects of cold and hot thermal therapies on the skin inflammation of trimellitic anhydride- (TMA-) induced dermatitis-like contact hypersensitivity (CHS) mouse model, or the mechanism of thermal therapy on allergic skin inflammation. Therefore, in this study, to reveal the anti-inflammatory effect of thermal therapy and its mechanism on TMA-induced CHS, we analyzed ear-swelling response (ear edema), vascular permeability, serum IgE levels, histological examination, and histamine and Th2 cytokine levels. Cold thermal therapy reduced the ear-swelling response, the vascular permeability, the serum IgE levels, and the infiltration of eosinophils and mast cells as well as the mast cell degranulation. To determine the mechanism by which cold thermal therapy inhibits allergic skin inflammation, detailed studies were carried out revealing that cold thermal therapy suppressed IL-4 and IL-5 secretion and mast cell activation. These results indicated that cold thermal therapy cures skin inflammation of TMA-induced CHS by decreasing Th2 cytokine release, especially IL-4 and IL-5, and mast cell activation. These data suggest that new insight into the mechanism of robust therapeutic effects of cold thermal therapy against allergic dermatitis, and cold thermal therapy may prove to be a useful therapeutic modality on allergic inflammatory diseases as traditional use as well as Th2- or mast cell-mediated allergic responses.

Modeling Skin Injury from Hot Rice Porridge Spills

The present work analyzes skin burns from spills of hot rice and milk products. The traditional Norwegian rice porridge serves as an example. By testing spills on objects emulating an arm, it was concluded that spills were seldom thinner than 3 mm, and stayed in place due to the viscosity of the porridge for more than one minute. The Pennes bioheat equation was solved numerically for such spills, including heat conduction to the skin and convective heat losses from the porridge surface. Temperatures were analyzed in the porridge and skin layers, and the resulting skin injury was calculated based on the basal layer temperature. Parameters influencing burn severity, such as porridge layer thickness, porridge temperature, removal of the porridge and thermal effects of post scald tempered (15 °C) water cooling were analyzed. The spilled porridge resulted in a prolonged heat supply to the skin, and the skin injury developed significantly with time. The porridge temperature turned out to be the most important injury parameter. A 70 °C porridge temperature could develop superficial partial-thickness burns. Porridge temperatures at processing temperatures nearly instantly developed severe burns. It was demonstrated that prompt removal of the hot porridge significantly reduced the injury development. The general advice is to avoid serving porridge and similar products at temperatures above 65 °C and, if spilled on the skin, to remove it quickly. After such scald incidents, it is advised to cool the injured area by tempered water for a prolonged period to stimulate healing.

Modeling Skin Injury from Hot Spills on Clothing

The present work analyzes scald burns from hot beverages, such as coffee and tea, spilled on the lap, i.e., an incident that may occur in daily life. The Pennes bioheat equation is solved numerically for small spills wetting the clothing, i.e., the fabric prevents the spilled liquid from draining away. Temperatures are analyzed in the wetted fabric and the skin layers and the resulting skin injury is calculated based on the basal layer temperature. Parameters influencing burn severity, such as clothing thickness, liquid temperature, removal of fabric and thermal effects of post scald water cooling are analyzed. The fabric cools the water some but represents a threat since the entrapped water results in a prolonged heat supply. The liquid temperature turned out to be the most important injury parameter, where liquid temperature of about 80–85 °C seems to be a limit for developing superficial partial-thickness burns in the present minimum case, i.e., where the liquid just wets the fabric. Spilling water in excess of just wetting the fabric, more severe burns will develop at lower liquid temperatures due to the prolonged heat supply. Higher liquid temperatures will nearly instantly develop more severe burns. It is demonstrated that removal of the clothing within the first seconds after the spill may significantly reduce the scalding severity. The general advice is therefore to avoid excessive heating of beverages and, if the beverage is spilled, to quickly remove the wetted clothing. Prolonged tempered water cooling is advised to improve the healing processes.

Modeling Burns for Pre-Cooled Skin Flame Exposure

On a television show, a pre-cooled bare-skinned person (TV host) passed through engulfing kerosene flames. The assumption was that a water film should protect him during 0.74 s flame exposure in an environment of 86 kW/m² heat flux. The TV host got light burn inflammation on the back, arms and legs. The present work studies skin temperatures and burn damage integral of such dangerous flame exposure. The skin temperature distribution during water spray pre-cooling, transport to the flames, flame exposure, transport to the water pool, and final water pool cooling is modelled numerically. Details of the temperature development of the skin layers are presented, as well as the associated damage integral. It is shown that 5 °C water spray applied for a 30 s period pre-cooled the skin sufficiently to prevent severe skin injury. Soot marks indicate that the water layer evaporated completely in some areas resulting in skin flame contact. This exposed dry skin directly to the flames contributing significantly to the damage integral. It is further analyzed how higher water temperature, shorter pre-cooling period or longer flame exposure influence the damage integral. It is evident that minor changes in conditions could lead to severe burns and that high heat flux levels at the end of the exposure period are especially dangerous. This flame stunt should never be repeated.

Flame time of a cigarette lighter to achieve temperature capable of inflicting a burn

OBJECTIVE

Cigarette lighters are frequent vectors in intentional contact burns. Time and temperature needed to cause thermal injury are considered to differentiate accidental from inflicted burns. This study examines the minimum time needed to heat a cigarette lighter's top to temperatures capable of inflicting any clinically visible skin burn. This information could be useful in child abuse and other forensic cases.

METHODS

A literature search was performed to establish the time and temperature at which partial/full thickness skin burns are acquired, regardless of vector. Using a thermocouple, the temperature of the top of two common lighters was measured at ten second intervals while sustaining maximal flame held both upright and sideways and during cooling once the flame was extinguished.

RESULTS

In the literature, the lowest temperatures documented to cause burns in one second were 69°C-70°C for transepidermal or partial thickness burns. From an ambient temperature prior to flame ignition, it took over 50s for the lighter tops to reach 60°C when held upright. After 180s, the lighters were shut off. It then took less than 60s for the lighters to cool to less than 60°C. The BIC lighter held to the side heated to 60°C in about 15s and needed over 100s to cool to under 60°C.

CONCLUSIONS

Cigarette lighter burns are often blamed on non-intentional occurrences. At least 50s of sustained flame is needed to heat typical cigarette lighter tops to temperatures capable of inflicting clinically visible skin burns. This time is longer than the time required to light a cigarette. Therefore, for a cigarette lighter to inflict a contact burn injury, there needs to be intent and preparation, making accidental cigarette lighter burns unlikely.

Heat effects on drug delivery across human skin

INTRODUCTION

Exposure to heat can impact the clinical efficacy and/or safety of transdermal and topical drug products. Understanding these heat effects and designing meaningful in vitro and in vivo methods to study them are of significant value to the development and evaluation of drug products dosed to the skin.

AREAS COVERED

This review provides an overview of the underlying mechanisms and the observed effects of heat on the skin and on transdermal/topical drug delivery, thermoregulation and heat tolerability. The designs of several in vitro and in vivo heat effect studies and their results are reviewed.

EXPERT OPINION

There is substantial evidence that elevated temperature can increase transdermal/topical drug delivery. However, in vitro and in vivo methods reported in the literature to study heat effects of transdermal/topical drug products have utilized inconsistent study conditions, and in vitro models require better characterization. Appropriate study designs and controls remain to be identified, and further research is warranted to evaluate in vitro-in vivo correlations and the ability of in vitro models to predict in vivo effects. The physicochemical and pharmacological properties of the drug(s) and the drug product, as well as dermal clearance and heat gradients may require careful consideration.

Heat Transfer in Health and Healing

Our bodies depend on an exquisitely sensitive and refined temperature control system to maintain a state of health and homeostasis. The exceptionally broad range of physical activities that humans engage in and the diverse array of environmental conditions we face require remarkable strategies and mechanisms for regulating internal and external heat transfer processes. On the occasions for which the body suffers trauma, therapeutic temperature modulation is often the approach of choice for reversing injury and inflammation and launching a cascade of healing. The focus of human thermoregulation is maintenance of the body core temperature within a tight range of values, even as internal rates of energy generation may vary over an order of magnitude, environmental convection, and radiation heat loads may undergo large changes in the absence of any significant personal control, surface insulation may be added or removed, all occurring while the body's internal thermostat follows a diurnal circadian cycle that may be altered by illness and anesthetic agents. An advanced level of understanding of the complex physiological function and control of the human body may be combined with skill in heat transfer analysis and design to develop life-saving and injury-healing medical devices. This paper will describe some of the challenges and conquests the author has experienced related to the practice of heat transfer for maintenance of health and enhancement of healing processes.

Skin temperatures generated following plaster splint application

Heat is generated during the exothermic reaction associated with plaster splint application. The amount of heat generated is affected by the plaster thickness, dipping water temperature, and extremity elevation method. The authors assessed the effect of these variables on skin and plaster temperatures. Short-leg posterior splints were applied to noninjured extremities on a volunteer using 2 protocols. Following splint application, the splinted leg was elevated in 4 ways: on plastic-covered urethane pillows in cotton pillowcases, on cotton blankets, on ice packs (short-term cryotherapy) placed on top of cotton blankets, or with heel elevation to promote free air circulation. Skin and plaster temperatures were monitored at 1-minute intervals. The maximum skin temperature generated and the average time that skin temperature was 40 °C or higher were recorded.

Anatomy-driven design of a prototype video laryngoscope for extremely low birth weight infants

Extremely low birth weight (ELBW) infants frequently require endotracheal intubation for assisted ventilation or as a route for administration of drugs or exogenous surfactant. In adults and less premature infants, the risks of this intubation can be greatly reduced using video laryngoscopy, but current products are too large and incorrectly shaped to visualize an ELBW infant's airway anatomy. We design and prototype a video laryngoscope using a miniature camera set in a curved acrylic blade with a 3×6-mm cross section at the tip. The blade provides a mechanical structure for stabilizing the tongue and acts as a light guide for an LED light source, located remotely to avoid excessive local heating at the tip. The prototype is tested on an infant manikin and found to provide sufficient image quality and mechanical properties to facilitate intubation. Finally, we show a design for a neonate laryngoscope incorporating a wafer-level microcamera that further reduces the tip cross section and offers the potential for low cost manufacture.

Bath-water scalds in children and thermostatic mixer valves

BACKGROUND

Scalds in children caused by hot bath-water have been virtually eliminated in countries where thermostatic mixer valve (TMV) devices have been introduced. We aimed to determine the frequency and severity of these injuries in our region and estimate reduction in workload and cost if TMVs were introduced in the future.

METHODS

A retrospective review was conducted of case-notes for all bath-water scalds patients aged under 16 years, admitted to the Northern Regional Burn Centre from the 1 January 1997 until 1 January 2005.

RESULTS

One hundred and twenty-five patients were admitted over this period. Their average+/-S.D. age was 35.7+/-27.23 months. Scalds ranged from 0.5 to 45% total burn surface area (mean 9.3+/-9.15%). These patients stayed in hospital for an average of 6.3+/-5.58 days and 18 (14.4%) required tangential excision and split skin grafting.

DISCUSSION

These injuries are: painful, psychologically disturbing and potentially preventable. The care of these children has significant cost implications, which could be reduced with the introduction of proposed legislation to enforce the installation of TMVs into all newly built houses. We are in favour of such legislation to prevent any further unnecessary suffering and cost arising from these accidents.

The UK pre-hospital management of burn patients: current practice and the need for a standard approach

INTRODUCTION

In any system of burn care, first-aid, packaging and transportation of the burn injured patient from outside of hospital is a most important contribution to the successful management and outcome. This study aimed to assess the current initial care of burn patients given by the statutory ambulance services and then compare this to a survey of opinions among the plastic surgery and burns consultants in the United Kingdom (UK).

METHODS

In 1999, each of the UK ambulance services was contacted via a postal questionnaire. A similar survey was sent to all of the plastic surgery consultants within the UK (taken from the specialist register) therefore, canvassing the plastic surgeons who deal less commonly with burn patients as well as the burns units.

RESULTS

A total of 58% of ambulance services said that they had no treatment policy for burns patients; 97% sent patients to their nearest A&E department; 84% of services employed cooling; 12 different types of dressing were used for burn patients; 74% of services used nalbuphine hydrochloride and 97% used entonox; 74% services gave oxygen to all burn patients; 90% cannulated patients, with or without fluid administration. Plastic surgical opinion indicated that the most important aspects of basic first-aid should include: stopping the burning process; cooling (15 min (median)); airway, breathing and circulation assessment; clothing removal and dressings (clingfilm). Oxygen need not be given to all patients, but they should be kept warm and administered entonox and/or intravenous morphine. Most surgeons felt that patients should be taken to the nearest A&E and the majority of surgeons caring for this large group of patients did not have good and regular liaison with their local ambulance service.

CONCLUSIONS

There seems to be a wide variation in the basic approach to the first-aid and pre-hospital care of burns patients. A significant improvement in management for this large and important group of patients is achievable, if a standard approach across all ambulance services could be achieved.

Thermal injury and child abuse: the medical evidence dilemma

The defense of the innocent, as well as the prosecution of the guilty, is a basic premise of American justice. This article reviews nine cases defended by the public defender system, in which the authors were involved, that illustrate some of the pitfalls in making the diagnosis of child abuse and/or neglect caused by thermal injury. The basis for the defense is also discussed, together with the biologic, engineering, and socioeconomic factors. The definition of child abuse and/or neglect is discussed, as is the devastating and long-lasting label of a false accusation, much less false imprisonment. In this regard this review concludes that professionals with thermal injury expertise must become involved in the judicial process if justice is to prevail.

The continuing risk of domestic hot water scalds to the elderly

Elderly people are particularly at risk of accidents in the home and with an ageing population, they constitute a large proportion of scald victims. We have seen several elderly patients every year in our own unit who had sustained domestic hot water burns. We decided to ascertain the temperature of water in the private homes of elderly people and in residential care homes in our community. Twenty-five private homes and 14 residential care homes were visited and peak water temperatures were measured in the kitchens and bathrooms. Only one private home and one residential home had water below 45 degrees C. It is recommended that water should be delivered at less than 43 degrees C. We conclude that water is dangerously hot. However, if water is stored at a temperature of less than 60 degrees C there is a risk of infection with Legionella pneumophila. Existing regulations governing the use of 'fail safe' thermostatic mixing devices must be enforced and extended to cover domestic hot water systems.

Burns sustained by hot bath and shower water

An 8-year retrospective review of patients admitted to Stoke Mandeville Hospital (Aylesbury, UK) because of burns sustained by hot bath and shower water was undertaken. Fifty-seven patients of all ages were identified and stratified into paediatric (< 16 years) and adult groups. Nine patients died. The main characteristics of the burns, causes and outcomes of treatment were analysed for each group. Children were predominantly under three years of age (83%), sustaining most frequently only superficial burns (41%) with areas of less than 10% total body surface area (72%). Parents' supervision was inadequate in 85% of cases. Eighty-three percent of the adults were over the age of 60. Two thirds had some form of psycho-motor disorder that predisposed to an accident which should have been anticipated. In comparison to children, adults suffered more extensive and deeper burns that resulted in a mortality of 44% (8/18). In both groups, the lower parts of the body were most frequently involved. The observed decline in the number of admissions for the period of investigation is encouraging. It supports an ultimate need for further development and actual implementation of preventative measures for hot water burns in the homes of people who are at greatest risk.

Issues in modeling thermal alterations in tissues

Thermal injury in living tissues is commonly modeled as a rate process in which cell death is interpreted to occur as a function of a single kinetic process. Experimental data indicate that multiple rate processes govern the manifestation of injury and that these processes may act over a broad spectrum of time domains. Injury is typically computed as a dimensionless function (omega) of the temperature time history via an Arrhenius relationship to which numerical values are assigned based on defined threshold levels of damage. However, important issues central to calculation and interpretation of the omega function remain to be defined. These issues include the following: how is temperature identified in time and space within a tissue exposed to thermal stress; what is the biophysical and physiological meaning of a quantitative value for omega; how can omega be quantified in an experimental system; how should omega be scaled between graded levels of injury; and what are the differences in injury kinetics between unit volume- and unit surface area-governed processes of energy deposition into tissue to cause thermal stress? This paper addresses these issues with the goal of defining a more rigorous and comprehensive standard for modeling thermal injury in tissues.

Cast-saw burns: comparison of technique versus material versus saws

Inadvertent cast-saw burns are attributable to inadequately padded casts, improper technique, or uncooperative patients. Cast-saw blade temperatures recorded while splitting plaster and fiberglass casts are elevated to a degree that would increase the risk of a second- or third-degree burn. Using standardized plaster and fiberglass cast models, this study attempted to determine whether the elevated temperature was a product of the saw, blade design, blade material, technique of cast removal, or casting materials. The results demonstrated that cast-saw blades manufactured with stainless steel are poorly suited for a device that uses friction to separate a cast. Modifications to the technique and varying the cast-saw models did not reduce the blade temperature consistently to <120-130 degrees F during normal operations.

Thirty-five years of paediatric scalds: are lessons being learned?

All paediatric scalds admitted in 1991 to the Welsh Centre for Burns and Plastic Surgery have been analysed retrospectively and the results compared with similar studies from this centre reported in 1956 and 1984. This data was compared with similar reports from 6 other world-wide centres. Despite a modest population increase in Wales, the number of admissions has increased almost 50% in 35 years. Boys are more commonly affected and up to 67% of scalds occur in children under 2 years of age. The number of scalds from teapots has fallen from 20.8% to 2.7%, in contrast to scalds from cups of hot liquid which have increased from 8.9% to 42.5% over the 35-year period. Scalds from hot baths are rare in Holland and Denmark, in contrast to a 15.8% incidence in our centre. Hot kettles are a common cause of scalds, accounting for up to 28% of scalds in all the series reviewed. The incidence of this injury has not decreased over the last 35 years. Recommendations are made about improved health and safety education for parents, the use of coiled kettle flexes, the temperature of stored water which should not exceed 60 degrees C, and the fitting of thermostatic mixer taps to new houses and institutions, in an effort to decrease the incidence of paediatric scalds.

Patterns of scald injuries

OBJECTIVES

To describe common patterns of bath water scald injuries in children, to examine differences between accidental and non-accidental bath water scalds in children, and to examine potential for prevention.

DESIGN

A two year six month retrospective analysis of admissions to a specialist burns unit.

SETTING

The Burns Unit, St Lawrence Hospital, Chepstow serving children from south and west Wales.

SUBJECTS

Sixty eight children attending the Burns Unit for treatment of bath related scald injuries.

RESULTS

Bath scalds in children under 5 years of age was the cause of 14.7 per 100,000 children being admitted to the specialist burns unit in a year. The majority of the children were injured by falling in the bath but the tap was turned on by seven children themselves and by 10 siblings. Six children put hands in the hot water and two children were accidentally put into bath water that was too hot and were quickly withdrawn. Four children suffered probably non-accidental immersion scald injuries from hot water. They were characterised by a clear tide mark, a story that did not fit the injuries, associated injuries, and by symmetrical lesions. Accidental scalds were irregular geographical injuries and were asymmetrical.

CONCLUSIONS

Bath scalds are a significant problem in children under 5 years. Their prevention should be part of an injury control programme on a local and national level. The best way to achieve this would be by reducing the temperature in domestic hot water tanks. The recognition of non-accidental bath scalds can be assisted by the pointers outlined and should be done in a multidisciplinary way with plastic surgeons, paediatricians, and social workers working together.

Entrapment against radiators--an underestimated burn hazard to the elderly

Five cases of burns caused by residents of nursing homes falling out of bed and becoming trapped against radiators or hot pipes are reported. The current guidelines for nursing homes in relation to heating surfaces are reviewed and recommendations are made on how this hazard can be avoided.

Normal human salivary gland cells produce carcinoembryonic antigen-related antigen in collagen gels

The Arrhenius and thermal isoeffective dose (TID) models are the two most commonly used models for predicting hyperthermic injury. The TID model is essentially derived from the Arrhenius model, but due to a variety of assumptions and simplifications now leads to different predictions, particularly at temperatures higher than 50°C. In the present study, the two models are compared and their appropriateness tested for predicting hyperthermic injury in both the traditional hyperthermia (usually, 43–50°C) and thermal surgery (or thermal therapy/thermal ablation, usually, >50°C) regime. The kinetic parameters of thermal injury in both models were obtained from the literature (or literature data), tabulated, and analyzed for various prostate and kidney systems. It was found that the kinetic parameters vary widely, and were particularly dependent on the cell or tissue type, injury assay used, and the time when the injury assessment was performed. In order to compare the capability of the two models for thermal injury prediction, thermal thresholds for complete killing (i.e., 99% cell or tissue injury) were predicted using the models in two important urologic systems, viz., the benign prostatic hyperplasia tissue and the normal porcine kidney tissue. The predictions of the two models matched well at temperatures below 50°C. At higher temperatures, however, the thermal thresholds predicted using the TID model with a constant R value of 0.5, the value commonly used in the traditional hyperthermia literature, are much lower than those predicted using the Arrhenius model. This suggests that traditional use of the TID model (i.e., R=0.5) is inappropriate for predicting hyperthermic injury in the thermal surgery regime (>50°C). Finally, the time-temperature relationships for complete killing (i.e., 99% injury) were calculated and analyzed using the Arrhenius model for the various prostate and kidney systems.

Determination of maximum temperatures that can be tolerated on contact with hot surfaces

The knowledge that there is a risk of burning from touching hot surfaces is certainly nothing new. However, little progress has been made so far on the matter of the minimum surface temperature at which burning can be expected. Preparatory work on determining these threshold values has now been finished by the Berufsgenossenschaftlichen Institut fur Arbeitssicherheit (Occupational Safety Institute of Industrial Injuries Insurance Institutes). The figures are included in UVV "Hitze" (Accident Prevention Regulation on "Heat").

Prompt cooling of burned areas: a review of benefits and the effector mechanisms

Arguably one of the oldest recorded methods of treating burns is still recommended today, namely prompt cooling of the injured part, usually in cold water. Such therapy was recommended by Galen (AD 129-199) and Rhazes (AD 852-923) Earle (1799) and by Sorensen (1967). As a first aid measure it has numerous advocates in the 1970s and 1980s. Almost certainly subjective considerations initiated this form of treatment and only within recent times have objective studies confirmed the beneficial effects of a more rapid reduction in tissue temperature and thus severity of injury.

The role of contact resistance in skin burns

Analytical predictions of temperature-time histories of skin contacts with a number of materials are presented. Comparison with available experimental results show that correlations are much improved if a contact resistance is included in the analysis. Some simple experiments are also presented which indicate that the contact resistance between skin and a hard surface for a moderate contact pressure is of the order of 1000 W/m2K.