Date of Award

2021

Degree Name

Doctor of Philosophy (School of Physiotherapy)

Schools and Centres

Physiotherapy

First Supervisor

Associate Professor Dale Edgar

Second Supervisor

Winthrop Professor Fiona Wood

Third Supervisor

Mr Jeremy Rawlins

Abstract

Burn injury is a unique trauma. The inflammatory process initiated with burn injury adversely influences all of the Starling equation variables, resulting in increased transvascular fluid filtration, so that oedema as a product of burn injury is more readily formed than in other forms of trauma. Localised wound oedema forms due to minor burn injury, with increasing systemic oedema associated with increased size of burn. It is now recognised that a marked inflammatory and immune response is created with non-severe burn injury, indicating a systemic component with all burns. The effect of oedema formation on the course of the burn healing is well described in the literature, due to its impact on the zone of stasis in the wound and its potential to result in progressive tissue loss or conversion if poorly managed. Burn conversion leads to an increase in the area and depth of the burn wound, necessitating surgical intervention, which increases the risk of scarring. Burn scarring may lead to altered function and poor aesthetic outcomes, which have the potential to adversely affect patient psychological well-being. Despite the influence of oedema on the healing of the burn wound and therefore the scar worn for life, there is little evidence to guide clinicians who aim to proactively manage this oedema, with only two published, controlled trials investigating methods to improve peripheral oedema in burn injury.

The aim of the series of studies described in this thesis is to provide a holistic approach to the management of oedema following acute burn injury. To be able to effectively treat oedema, the clinician needs to be able to accurately assess the affected limb and wound for oedema. Oedema management in burn injury is often based on the clinicians’ preference of intervention, without good understanding of the optimal parameters of application or efficacy. Therefore, evidence is required for optimising the management of oedema in the acute burn injured patient.

Furthermore, the hand’s unique anatomical structure that produces functional dexterity adds complexity to the assessment and management of oedema formation in the hand. Burn injury to the hand is common, as hands provide interaction with the world, and are generally vulnerable during activities of daily living. In the event of major accidents, the hands are reflexively used to protect the face and body, further predisposing them to significant injury.

The ability to accurately measure oedema guides clinicians in their treatment of acute burn wound oedema. Current objective measures of oedema often lack sensitivity, increase pain, introduce a risk of infection from equipment contact with open wounds, or are cumbersome for repeated use in the clinical environment. They are also influenced by the cooperation of the patient, and burn injury often results in significant pain, impaired movement, and may require the use of medications that modify behaviour. As a result, oedema is usually assessed visually or through palpation of the tissue, noting the loss of skin creases or pitting of soft tissue. These assessments are subjective based on the clinician’s experience and do not provide objective measures that can be repeated between testers or between sessions. Demonstrating the effectiveness of proactive oedema management following acute burn injury is therefore dependent on the ability to accurately assess the oedema using a valid, reliable and sensitive objective measure.

There is a lack of high-quality prospective studies investigating oedema management techniques in burn injury populations. In a 2011 systematic review, there was only one published randomised control trial, which investigated the use of electrical stimulation in addition to standard interventions for managing hand burn oedema, while a second conference presentation was reported as part of the review. There have been no further published studies in this space, providing clinicians with little guidance as to the optimal parameters to manage oedema in this challenging injury cohort. Measuring oedema in this patient group is similarly challenging.

The study series in this thesis addresses the challenge of measuring hand burn oedema and wound healing.

Bioimpedance spectroscopy (BIS) is a technology that has demonstrated reliability and validity for measuring whole body and limb oedema in burns patients during fluid resuscitation, and is sufficiently sensitive to measure oedema change with wound healing. Another BIS variable, Phase Angle, is validated to be a measure of cell health, as it measures the flow of current across the cell with respect to the voltage. Increased lag in the current is the result of increased cell mass and cell wall integrity (a healthier cell), resulting in an increased Phase Angle. This has been demonstrated to increase with healing in chronic wound populations, but has not been validated in acute burn injury.

The first study in this thesis is a method validation study, investigating the measurement of hand volumes using a novel application of BIS. A technique to measure hand volumes using BIS has been described previously, however the burn injured hand is compromised by wounds. The guidelines for the use of BIS require that electrodes are placed on intact skin. The study compared different electrode configurations on the hand and arm to the previously described configuration in a non-injured population, to determine if different electrode configurations are valid for measuring hand volumes. The key findings of this study were that, when compared to previously described electrode positions on the dorsum of the hand and forearm, alternative electrode combinations on the volar surface of the hand and forearm, and an electrode array on the palm of the hand and the dorsum of the forearm, were both valid for measuring hand oedema volumes in an uninjured population. These outcomes provide novel evidence to guide electrode placements to measure hand volume using BIS where wounds precluded the use of standard electrode arrays.

The second study in this series is a validation study, informed by and used the electrode positions assessed in the first study, to determine the validity and reliability of BIS for measuring hand (oedema) volumes in a burn injured population. Repeated hand volume measures were obtained in 100 patients presenting with hand burn injury with BIS, and with water displacement volumetry as a gold standard comparison. The results of this study demonstrated that the electrode positions assessed as valid for measuring hand volumes in an uninjured population in the first study, were valid, reliable and sensitive for measuring oedema in the hand following burn injury, showing high correlation with the gold standard comparator. This technique was used to assess the primary outcome – oedema volume change – in the third study of this series.

The following studies in this thesis are intervention research, investigating techniques designed to proactively manage oedema in acute burn injury.

The third study described in this thesis is the first randomised controlled trial to investigate different methods of applying compression to the hand to manage acute burn oedema. Compression is a commonly used technique to control oedema, reported to be applied based on clinician preference, which is dependent on the way each clinician was taught. In this study, 100 patients (the largest of its kind to the best of my knowledge), presenting with burn injury involving a portion of the hand were randomised to receive one of three commonly used methods of applying compression, to provide evidence as to which is the most effective at controlling acute burn wound oedema in the hand. In this study, the two most common methods of fabricating a custom compression glove using cohesive bandage were shown to be both equally effective at reducing post burn oedema in the hand, and both were more effective for reducing hand burn oedema than the control condition being an off the shelf compression glove. The patients in this study were also provided education regarding exercise to maintain function and promote oedema reduction, oedema management advice including elevation of the hand above the level of the heart at rest, and ensuring normal use of the hand while respecting the wound environment to minimise the risk of infection. These interventions resulted in significantly greater hand range of movement between test sessions, and a significant improvement in the QuickDASH (Disability of Arm, Shoulder and Hand) patient reported outcome measure.

The effect of a low energy, long duration electrical stimulation on the acute burn wound was investigated in study four. Electrical stimulation has been demonstrated to improve the rate of healing of chronic wounds, and aid the reduction of oedema in a number of populations, including patients with hand burn injury when used in addition to standard physiotherapy. The novel application of electrical stimulation in this study utilised a small patient applied stimulation device for more than 20 hours per day for a period of up to 14 days, with the current applied across the wound with electrodes placed either side of the injured tissue on intact skin. This was designed as a within-patient control, randomised trial. Patients with similar size and similar depth burns to multiple limbs participated in this study. Electrical stimulation was applied to one wound, with the contralateral wound serving as the control wound. The outcomes investigated were change in oedema, as measured by the BIS variable R0, measuring the impedance of the extra-cellular fluid; and wound healing, measured by the BIS variable Phase Angle, and compared to clinical photography of the wounds, which were assessed by a consultant burns surgeon to determine wound re-epithelialisation, or healing. Phase Angle and wound impedance were demonstrated to be associated with wound healing. Electrical stimulation applied to a minor burn was shown to increase the rate of oedema reduction in the wound compared to the control wound, and increased Phase Angle at a faster rate than in the control wound, indicating an increase in cell and tissue health.

This thesis presents a study series whereby the first two studies validated a new method of measuring hand burn oedema quickly, with minimal imposition on the patient. This method was demonstrated as viable and applicable in acute burn patients, in both research and clinical practice contexts, and informed the ensuing studies in this series. The final two studies presented in this thesis are randomised controlled trials investigating the proactive management of oedema in acute burn injury, and contribute significant new knowledge to the literature, providing guidance to the burn clinician who manages acute oedema to prevent conversion of the burn wound and deterioration in function.

When presented with a hand burn injury, the clinician will be able to appropriately manage the ensuing oedema with a custom compression glove fabricated using a cohesive bandage with either of the most common methods therapists are taught. In addition, in minor burn wounds, the use of a small, easy to use, low energy long duration electrical stimulation device as an adjunct to standard burn wound care, will increase oedema reduction and improve the rate of wound healing compared to standard wound care alone.

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