The diagnosis of early pressure sores: report of the pilot study

Technologies to monitor the health of loaded skin tissues

There are many situations where the skin and underlying soft tissues are compromised by mechanical loading in the form or pressure, or pressure in combination with shear. If sustained, this can lead to damage in the tissues particularly adjacent to bony prominences, resulting in chronic wounds. An array of bioengineering technologies have been adopted to assess the integrity of loaded soft tissues. This paper aims to review these approaches for the quantification, simulation and early detection of mechanically-induced skin damage. The review considers different measurements at the interface between the skin and support surface/medical device, involving pressure, shear, friction and the local microclimate. The potential of the techniques to monitor the physiological response of the skin to these external stimuli including biophysical measurement devices and sampling of biofluids are critically analysed. In addition, it includes an analysis of medical imaging technologies and computational modelling to provide a means by which tissue deformation can be quantified and thresholds for tissue damage defined. Bioengineering measurement and imaging technologies have provided an insight into the temporal status of loaded skin. Despite the advances in technology, to date, the translation to clinical tools which are robust and cost effective has been limited. There is a need to adapt existing technologies and simulation platforms to enable patients, carers and clinicians to employ appropriate intervention strategies to minimise soft tissue damage.

Accuracy of ultrasound, thermography and subepidermal moisture in predicting pressure ulcers: a systematic review

OBJECTIVE

Our aims were to: establish the clinical significance of ultrasound, thermography, photography and subepidermal moisture (SEM) measurement; determine the accuracy of ultrasound, thermography, photography and SEM measurement in detecting skin/tissue damage; determine the relative accuracy of one of these assessment methods over another; make recommendations for practice pertaining to assessment of early skin/tissue damage.

METHOD

The following databases, Cochrane Wounds Group Specialised Register, The Cochrane Central Register of Controlled Trials, Ovid MEDLINE, Ovid EMBASE, Elsevier version, EBSCO CINAHL, ClinicalTrials.gov , WHO International Clinical Trials Registry (ICTR) and The EU Clinical Trials Register were searched for terms including; thermography, ultrasound, subepidermal moisture, photograph and pressure ulcer.

RESULTS

We identified four SEM, one thermography and five ultrasound studies for inclusion in this review. Data analysis indicated that photography was not a method which allowed for the early prediction of PU presence. SEM values increased with increasing tissue damage, with the sacrum and the heels being the most common anatomical locations for the development of erythema and stage I PUs. Thermography identified temperature changes in tissues and skin that may give an indication of early PU development; however the data were not sufficiently robust. Ultrasound detected pockets of fluid/oedema at different levels of the skin that were comparable with tissue damage. Thus, SEM and ultrasound were the best methods for allowing a more accurate assessment of early skin/tissue damage. Using the EBL Critical Appraisal Tool the overall validities of the studies varied between 33.3-55.6%, meaning that there is potential for bias within all the included studies. All of the studies were situated at level IV, V and VII of the evidence pyramid. Although the methodological quality of the studies warrants consideration, these studies showed the potential that SEM and ultrasound have in early PU detection.

CONCLUSION

SEM and ultrasound are promising in the detection and prediction of early tissue damage and PU presence. However, these methods should be further studied to clarify their potential for use more widely in PU prevention strategies.

Noninvasive imaging technologies for cutaneous wound assessment: A review

The ability to phenotype wounds for the purposes of assessing severity, healing potential and treatment is an important function of evidence-based medicine. A variety of optical technologies are currently in development for noninvasive wound assessment. To varying extents, these optical technologies have the potential to supplement traditional clinical wound evaluation and research, by providing detailed information regarding skin components imperceptible to visual inspection. These assessments are achieved through quantitative optical analysis of tissue characteristics including blood flow, collagen remodeling, hemoglobin content, inflammation, temperature, vascular structure, and water content. Technologies that have, to this date, been applied to wound assessment include: near infrared imaging, thermal imaging, optical coherence tomography, orthogonal polarization spectral imaging, fluorescence imaging, laser Doppler imaging, microscopy, spatial frequency domain imaging, photoacoustic detection, and spectral/hyperspectral imaging. We present a review of the technologies in use or development for these purposes with three aims: (1) providing basic explanations of imaging technology concepts, (2) reviewing the wound imaging literature, and (3) providing insight into areas for further application and exploration. Noninvasive imaging is a promising advancement in wound assessment and all technologies require further validation.

Repositioning for treating pressure ulcers

BACKGROUND

Pressure, from lying or sitting on a particular part of the body results in reduced oxygen and nutrient supply, impaired drainage of waste products and damage to cells. If a patient with an existing pressure ulcer continues to lie or bear weight on the affected area, the tissues become depleted of blood flow and there is no oxygen or nutrient supply to the wound, and no removal of waste products from the wound, all of which are necessary for healing. Patients who cannot reposition themselves require assistance. International best practice advocates the use of repositioning as an integral component of a pressure ulcer management strategy. This review has been conducted to clarify the role of repositioning in the management of patients with pressure ulcers.

OBJECTIVES

To assess the effects of repositioning patients on the healing rates of pressure ulcers.

SEARCH METHODS

For this third update we searched the Cochrane Wounds Group Specialised Register (searched 28 August 2014); The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 7); Ovid MEDLINE (2013 to August Week 3 2014); Ovid MEDLINE (In-Process & Other Non-Indexed Citations 29 August, 2014); Ovid EMBASE (2012 to 29 August, 2014); and EBSCO CINAHL (2012 to 27 August 2014).

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) comparing repositioning with no repositioning, or RCTs comparing different repositioning techniques, or RCTs comparing different repositioning frequencies for the review. Controlled clinical trials (CCTs) were only to be considered in the absence of RCTs.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed titles and, where available, abstracts of the studies identified by the search strategy for their eligibility. We obtained full versions of potentially relevant studies and two authors independently screened these against the inclusion criteria.

MAIN RESULTS

We identified no studies that met the inclusion criteria.

AUTHORS' CONCLUSIONS

Despite the widespread use of repositioning as a component of the management plan for individuals with existing pressure ulcers, no randomised trials exist that assess the effects of repositioning patients on the healing rates of pressure ulcers. Therefore, we cannot conclude whether repositioning patients improves the healing rates of pressure ulcers. The effect of repositioning on pressure ulcer healing needs to be evaluated.

Wound cleansing for pressure ulcers

BACKGROUND

Pressure ulcers (also called pressure sores, bed sores and decubitus ulcers) are areas of tissue damage that occur in the elderly, malnourished or acutely ill, who cannot reposition themselves. Pressure ulcers impose a significant financial burden on health care systems and negatively affect quality of life. Wound cleansing is considered an important component of pressure ulcer care.

OBJECTIVES

This systematic review seeks to answer the following question: what is the effect of wound cleansing solutions and wound cleansing techniques on the rate of healing of pressure ulcers?

SEARCH METHODS

For this third update, we searched the Cochrane Wounds Group Specialised Register (searched 3 January 2013); The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 12); Ovid MEDLINE (2010 to November Week 3 2012); Ovid MEDLINE (In-Process & Other Non-Indexed Citations December 31, 2012); Ovid EMBASE (2010 to 2012 Week 52); and EBSCO CINAHL (2010 to 21 December 2012).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing wound cleansing with no wound cleansing, or different wound cleansing solutions, or different cleansing techniques, were eligible for inclusion if they reported an objective measure of pressure ulcer healing.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data independently and resolved disagreements through discussion. A structured narrative summary of the included studies was conducted. For dichotomous outcomes, risk ratio (RR), plus 95% confidence intervals (CI) were calculated; for continuous outcomes, mean difference (MD), plus 95% CI were calculated. Meta analysis was not conducted because of the small number of diverse RCTs identified. Two review authors independently assessed each included study using the Cochrane Collaboration tool for assessing risk of bias.

MAIN RESULTS

One additional eligible study was identified from the updated searches, one study was added to the table of excluded studies. A total of three studies (169 participants) met the inclusion criteria for the review. No studies compared cleansing with no cleansing. Two studies compared different wound cleansing solutions. A statistically significant improvement in Pressure Sore Status Tool scores occurred for wounds cleansed with saline spray containing Aloe vera, silver chloride and decyl glucoside (Vulnopur) compared with isotonic saline (P value = 0.025), but no statistically significant change in healing was seen when water was compared with saline (RR 3.00, 95% CI 0.21 to 41.89). One study compared cleansing techniques; for pressure ulcers cleansed with pulsatile lavage, compared with sham (the lavage flow was directed into a wash basin positioned adjacent to the wound and not visible to the participants), there was a statistically significant reduction in ulcer volume at the end of the three week study period in the lavage group compared with the sham group (MD -6.60, 95% CI-11.23, -1.97).

AUTHORS' CONCLUSIONS

We identified three small studies addressing cleansing of pressure ulcers. One reported a statistically significant improvement in pressure ulcer healing for wounds cleansed with saline spray containing Aloe vera, silver chloride and decyl glucoside (Vulnopur) compared with isotonic saline solution, a further study reported no statistically significant change in healing was seen when wounds were cleaned with water was compared with saline. A final study compared pulsatile lavage with sham and found a significantly greater reduction in ulcer volume at the end of the study period in the lavage group compared with the sham group. The authors conclude that there is no good trial evidence to support use of any particular wound cleansing solution or technique for pressure ulcers.

Repositioning for treating pressure ulcers

BACKGROUND

Pressure, from lying or sitting on a particular part of the body results in reduced oxygen and nutrient supply, impaired drainage of waste products and damage to cells. If a patient with an existing pressure ulcer continues to lie or bear weight on the affected area, the tissues become depleted of blood flow and there is no oxygen or nutrient supply to the wound, and no removal of waste products from the wound, all of which are necessary for healing. Patients who cannot reposition themselves require assistance. International best practice advocates the use of repositioning as an integral component of a pressure ulcer management strategy. This review has been conducted to clarify the role of repositioning in the management of patients with pressure ulcers.

OBJECTIVES

To assess the effects of repositioning patients on the healing rates of pressure ulcers.

SEARCH METHODS

For this second update we searched the Cochrane Wounds Group Specialised Register (searched 23 May 2012); The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 5); Ovid MEDLINE (2010 to May Week 2 2012); Ovid MEDLINE (In-Process & Other Non-Indexed Citations May 22, 2012); Ovid EMBASE (2010 to 2012 Week 20); and EBSCO CINAHL (2010 to 16 May 2012).

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) comparing repositioning with no repositioning, or RCTs comparing different repositioning techniques, or RCTs comparing different repositioning frequencies for the review. Controlled clinical trials (CCTs) were only to be considered in the absence of RCTs.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed titles and, where available, abstracts of the studies identified by the search strategy for their eligibility. We obtained full versions of potentially relevant studies and two authors independently screened these against the inclusion criteria.

MAIN RESULTS

We identified no studies that met the inclusion criteria.

AUTHORS' CONCLUSIONS

Despite the widespread use of repositioning as a component of the management plan for individuals with existing pressure ulcers, no randomised trials exist that assess the effects of repositioning patients on the healing rates of pressure ulcers. Therefore, we cannot conclude whether repositioning patients improves the healing rates of pressure ulcers. The effect of repositioning on pressure ulcer healing needs to be evaluated.

Repositioning for treating pressure ulcers

BACKGROUND

Pressure, from lying or sitting on a particular part of the body, results in oxygen deprivation to the affected area. If a patient with an existing pressure ulcer continues to lie or bear weight on the affected area, the tissues become depleted of blood flow and there is no oxygen or nutrient supply to the wound, and no removal of waste products from the wound, all of which are necessary for healing. Patients who cannot reposition themselves require assistance. International best practice advocates the use of repositioning as an integral component of a pressure ulcer management strategy. This review has been conducted to clarify the role of repositioning in the management of patients with pressure ulcers.

OBJECTIVES

To assess the effects of repositioning patients on the healing rates of pressure ulcers.

SEARCH STRATEGY

We searched the following databases: the Cochrane Wounds Group Specialised Register (5 December 2008); the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 4); Ovid MEDLINE (1950 to November Week 3 2008); Ovid EMBASE (1980 to 2008 Week 49); and EBSCO CINAHL (1982 to November Week 4 2008).

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) comparing repositioning with no repositioning, or RCTs comparing different repositioning techniques, or RCTs comparing different repositioning frequencies for the review. Controlled clinical trials (CCTs) were only to be considered in the absence of RCTs.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed titles and, where available, abstracts of the studies identified by the search strategy for their eligibility. We obtained full versions of potentially relevant studies and two authors independently screened these against the inclusion criteria.

MAIN RESULTS

We identified no studies that met the inclusion criteria.

AUTHORS' CONCLUSIONS

Despite the widespread use of repositioning as a component of the management plan for individuals with existing pressure ulcers, no randomised trials exist that assess the effects of repositioning patients on the healing rates of pressure ulcers. Therefore, we cannot conclude whether repositioning patients improves the healing rates of pressure ulcers. The effect of repositioning on pressure ulcer healing needs to be evaluated.

Increasing heel skin perfusion by elevation

OBJECTIVE

To determine the efficacy of elevation in the primary prevention and treatment of pressure ulcers by studying the blood flow in tissue at risk of ulceration.

DESIGN

A prospective study was used to compare different preventative devices with an elevating prosthesis.

SETTING

: Wollongong Hospital Wollongong, New South Wales, Australia.

PARTICIPANTS

Normal subjects and subjects with vasculopathy were tested with their heel resting on a hospital bed, medical-grade lamb's wool, or a viscoelastic gel overlay, with or without the test prosthesis. Skin perfusion was measured throughout using a laser Doppler monitor.

INTERVENTION

A device designed to elevate the heel off the bed and distribute the weight of the leg and foot on the calf.

MAIN OUTCOME MEASURE

Heel capillary blood perfusion.

MAIN RESULTS

Perfusion in the heel was significantly greater when elevated than when using the other devices tested. The differences in mean red blood cell flux were significant, with P < .0001 for bed-normals, ie, subjects with no peripheral vascular disease on an alpha Xcell mattress overlay as the control with flux increasing from 7.6 to 163.1 arbitrary units (AU); P < .005 bed-vasculopathy, ie, subjects with peripheral vascular disease on an alpha Xcell mattress overlay as the control with flux increasing from 31.6 to 224.7 AU; P < .0001 viscoelastic overlay subjects where the viscoelastic overlay was the control with flux increasing from 26.6 to 291.4 AU; and P < .01 lamb's wool subjects where the lamb's wool was the control with flux increasing from 27.7 AU to 169.2 AU.

CONCLUSION

In this study, when the heels were elevated, tissue perfusion to that area was substantially increased. When the heel was transferred to the elevating splint, the heel capillary bed underwent reactive hyperemia, indicating the alleviation of tissue hypoxia. Elevation is therefore an important technique in pressure ulcer prevention and treatment and should be incorporated into health care practice.

Skin alterations of intact skin and risk factors associated with pressure ulcer development in surgical patients: A cohort study

BACKGROUND

The pathology literature suggests three types of pressure ulcer with six possible mechanisms leading to tissue breakdown. A limitation of current evidence is the difficulty in replicating the clinical situation and in determining the point at which a tissue assault becomes irreversible and results in tissue breakdown. In particular clinical observations of alteration in darkly pigmented skin, blanching erythema, non-blanching erythema and non-blanching erythema with other skin changes including induration, oedema, pain, warmth or discolouration have not been assessed in relation to subsequent skin/tissue loss and their pathophysiological and aetiological importance is not fully understood.

OBJECTIVES

To assess the validity of clinical signs of erythema as predictors of pressure ulcer development and identify variables which independently are predictive of Grade 2 pressure ulcer development.

DESIGN

Prospective cohort study.

PARTICIPANTS

109 general, vascular and orthopaedic hospital patients, aged over 55 years with an expected length of stay of 5 days were recruited. Of these 97 were pressure ulcer free at baseline and/or had complete follow-up including 59 women and 38 men with a median age of 75 years (range 55-95).

SETTING

Single centre large acute UK NHS hospital.

METHODS

To identify clinical signs of erythema predictive of skin loss, the odds of pressure ulcer development were examined using logistic regression. To identify variables independently predictive of Grade 2 pressure ulcer development logistic regression modeling was undertaken.

RESULTS

There was significantly increased odds of pressure ulcer development associated with non-blanching erythema (7.98, p=0.002) and non-blanching erythema with other skin changes (9.17, p=0.035). Logistic regression modeling identified non-blanching erythema, pre-operative albumin, weight loss, and intra-operative minimum diastolic blood pressure, as independent predictors of Grade > or =2 pressure ulcer development.

CONCLUSIONS

Non-blanching erythema with or without other skin changes is distinct from normal skin/blanching erythema and is associated with subsequent pressure ulcer development.

Wound cleansing for pressure ulcers

BACKGROUND

Pressure ulcers (also called pressure sores, bed sores and decubitus ulcers) are areas of tissue damage that occur in the very old, malnourished or acutely ill, who cannot reposition themselves. Pressure ulcers impose a significant financial burden on health care systems and negatively affect quality of life. Wound cleansing is considered an important component of pressure ulcer care.

OBJECTIVES

This systematic review seeks to answer the following question:What is the effect of wound cleansing solutions and wound cleansing techniques on the rate of healing of pressure ulcers?

SEARCH STRATEGY

We searched the Specialised Trials Register of the Cochrane Wounds Group (up to August 2005), and the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2005). We searched bibliographies of relevant publications retrieved. We contacted drug companies and experts in the field to identify studies missed by the primary search.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing wound cleansing with no wound cleansing, or different wound cleansing solutions, or different cleansing techniques, were eligible for inclusion if they reported an objective measure of pressure ulcer healing.

DATA COLLECTION AND ANALYSIS

Two authors extracted data independently and resolved disagreements through discussion and reference to the Cochrane Wounds Group editorial base. A structured narrative summary of the included studies was conducted. For dichotomous outcomes, relative risk (RR), plus 95% confidence intervals (CI) were calculated; for continuous outcomes, weighted mean difference (WMD), plus 95% CI were calculated. Meta analysis was not conducted, because of the small number of diverse RCTs identified.

MAIN RESULTS

No studies compared cleansing with no cleansing. Two studies compared different wound cleansing solutions: a statistically significant improvement in Pressure Sore Status Tool scores occurred for wounds cleansed with saline spray containing Aloe vera, silver chloride and decyl glucoside (Vulnopur) compared to isotonic saline (P value = 0.025), but no statistically significant change in healing was seen when water was compared to saline (RR 3.00, 95% CI 0.21, 41.89). One study compared cleansing techniques, but no statistically significant change in healing was seen for ulcers cleansed with, or without, a whirlpool (RR 2.10, 95% CI 0.93 to 4.76).

AUTHORS' CONCLUSIONS

We identified only three studies addressing cleansing of pressure ulcers. One noted a statistically significant improvement in pressure ulcer healing for wounds cleansed with saline spray containing Aloe vera, silver chloride and decyl glucoside (Vulnopur) when compared with isotonic saline solution. Overall, there is no good trial evidence to support use of any particular wound cleansing solution or technique for pressure ulcers.

Pathology, diagnosis, and classification of pressure ulcers: comparing clinical and imaging techniques

Pressure ulcer classification systems are based on the clinical manifestations of the skin and tissue layer affected rather than underlying pathology. The objective of this study was to compare the validity of the clinical grading of erythema (blanching and nonblanching) with a measurement of skin perfusion. Therefore, an exploratory study comparing erythema with laser Doppler imaging of the sacrum and buttock skin areas was undertaken. Acute and major elective general, vascular, and orthopedic surgical in-patients, aged 55 years or over with an expected length of hospital stay of 5 or more days were recruited. Fifty laser Doppler images from 37 patients were obtained and included in a discriminant analysis. Discriminant analysis suggested that blanching and nonblanching erythema were physiologically distinct from "normal" skin; clinically, these could be assessed with reasonable accuracy. Imaging also determined that high blood flow of differing intensity characterized blanching and nonblanching erythema. There was no evidence of the "no flow" phenomenon.

Reliability of pressure ulcer classification and diagnosis

AIM

To assess the inter-rater reliability of the PRESSURE Trial pressure ulcer diagnosis (>/=Grade 2) and skin classification for all grades between the clinical research nurse (CRN) team leader and CRNs working across different hospital sites; and CRNs and ward-based nurses.

BACKGROUND

The United Kingdom National Health Service Health Technology Assessment Programme has funded a multi-centre, randomized controlled trial to compare the clinical and cost-effectiveness of alternating pressure mattress overlays and mattress replacements - PRESSURE Trial. Outcome skin assessments were recorded by qualified ward-based nurses daily, and expert CRNs twice weekly.

METHOD

Paired assessments were undertaken and skin assessed on seven body sites. The per cent agreement between nurses in the diagnosis of a pressure ulcer was determined and the Kappa statistic and confidence intervals calculated. Per cent agreement between nurses in classifying skin for all grades was also determined.

RESULTS

Assessments were undertaken by 378 pairs: 16 paired patient assessments (107 site comparisons) by the CRN team leader and CRNs, and 362 paired patient assessments (2396 site comparisons) between CRNs and ward-based nurses. There was 100% agreement between the CRN team leader and CRNs in the diagnosis of a pressure ulcer, and the Kappa statistics indicated 'very good' agreement. There were only two (1.9%) disagreements in classifying skin for all grades between these nurses. The agreement in the diagnosis of a pressure ulcer between CRNs and ward-based nurses varied by skin site, ranging from 93.6% to 100%, with the Kappa statistics indicating 'good' and 'very good' agreement. However, there were 508 (21.2%) disagreements in classifying skin for all grades.

CONCLUSIONS

Overall agreement and Kappa statistics indicated 'very good' and 'good' agreement between expert nurses, and between expert nurses and qualified ward-based staff, respectively. However, the high prevalence of normal skin concealed clinically important disagreements in both the diagnosis of pressure ulcers and skin classification for all grades.

The role of pressure-redistributing equipment in the prevention and management of pressure ulcers

In response to a focus on education and research in pressure ulcer prevention, this paper reviews the evolution of pressure-redistributing mattresses and explores the effectiveness of interface pressure measurement in mattress development.

Examining the validity of pressure ulcer risk assessment scales: a replication study

Risk assessment scales (RASs) intended to identify patients most at risk of developing pressure ulcers have been widely used for many years. Numerous studies have evaluated their predictive validity but potential bias has been inherent in the design of all. To overcome these problems a simulation study was conducted in which clinical nurses were asked to identify the degree of risk experienced by four patients employing the three RASs discussed most frequently in the literature (Norton, Braden and Waterlow Scores). These findings were compared with nurses' clinical judgment rated on a visual analogue scale. The simulations consisted of high-resolution photographs accompanied by case studies of the patients. The nurses' scores were compared to estimates of risk generated by an expert panel. Nurses' clinical judgment agreed much more closely with expert opinion than any of the RASs. A replication study was undertaken to confirm these findings. One hundred and fifteen nurses participated in replication. Again the nurses' clinical judgment matched expert opinion much more closely than the results of the RASs. Replication also drew attention to a number of methodological issues which deserve consideration when using simulation to test the effectiveness of clinical tools and the need to establish adequate measures of external validity whenever use of this method is contemplated.

Comparison of pressure ulcer grading scales: a study of clinical utility and inter-rater reliability

Pressure ulcer grading scales are subjective measures of pressure damage. This study measured inter-observer agreement of the Stirling scale (1-digit and 2-digit versions) and the European Pressure Ulcer Advisory Panel Scale, using Cohen's kappa and percentage agreement. Clinical utility was also assessed. Thirty-five observations were made by two Registered Nurses on 30 adult in-patients. The levels of agreement obtained were better than those reported previously and this may be related to the methodology used. The 2-digit Stirling scale gave the best level of chance corrected agreement (kappa=0.457) and was the scale preferred by raters. The 1-digit Stirling scale performed least favourably. Qualitative data identified problems with scale construction relating to visualisation of the base of the wound, discolouration of the skin, abrasions and shallow ulcers. Whilst refinements in scale construction may improve rater reliability, there is a need to develop objective measures of pressure induced tissue damage.

Laser Doppler, speckle and related techniques for blood perfusion mapping and imaging

Laser Doppler velocimetry uses the frequency shift produced by the Doppler effect to measure velocity. It can be used to monitor blood flow or other tissue movement in the body. Laser speckle is a random interference effect that gives a grainy appearance to objects illuminated by laser light. If the object consists of individual moving scatterers (such as blood cells), the speckle pattern fluctuates. These fluctuations provide information about the velocity distribution of the scatterers. It can be shown that the speckle and Doppler approaches are different ways of looking at the same phenomenon. Both these techniques measure at a single point. If a map of the velocity distribution is required, some form of scanning must be introduced. This has been done for both time-varying speckle and laser Doppler. However, with the speckle technique it is also possible to devise a full-field technique that gives an instantaneous map of velocities in real time. This review article presents the theory and practice of these techniques using a tutorial approach and compares the relative merits of the scanning and full-field approaches to velocity map imaging. The article concludes with a review of reported applications of these techniques to blood perfusion mapping and imaging.