Impact of multilayered compression bandages on sub-bandage interface pressure: a model

Background

Multi-component medical compression bandages are widely used to treat venous leg ulcers. The sub-bandage interface pressures induced by individual components of the multi-component compression bandage systems are not always simply additive. Current models to explain compression bandage performance do not take account of the increase in leg circumference when each bandage is applied, and this may account for the difference between predicted and actual pressures.

Objective

To calculate the interface pressure when a multi-component compression bandage system is applied to a leg.

Method

Use thick wall cylinder theory to estimate the sub-bandage pressure over the leg when a multi-component compression bandage is applied to a leg.

Results

A mathematical model was developed based on thick cylinder theory to include bandage thickness in the calculation of the interface pressure in multi-component compression systems. In multi-component compression systems, the interface pressure corresponds to the sum of the pressures applied by individual bandage layers. However, the change in the limb diameter caused by additional bandage layers should be considered in the calculation. Adding the interface pressure produced by single components without considering the bandage thickness will result in an overestimate of the overall interface pressure produced by the multi-component compression systems. At the ankle (circumference 25 cm) this error can be 19.2% or even more in the case of four components bandaging systems.

Conclusion

Bandage thickness should be considered when calculating the pressure applied using multi-component compression systems.

Detection of volatile organic compounds using porphyrin derivatives

Seven different porphyrin compounds have been investigated as colorimetric gas sensors for a wide range of volatile organic compounds. The porphyrins examined were the free base and Mg, Sn, Zn, Au, Co, and Mn derivatives of 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-21H,23H-porphine. Chloroform solutions of these materials were prepared and changes in their absorption spectra induced by exposure to various organic compounds measured. The porphyrins that showed strong responses in solution were selected, and Langmuir-Blodgett films were prepared and exposed to the corresponding analytes. This was done to determine whether they are useful materials for solid state thin film colorimetric vapor sensors. Porphyrins that readily coordinate extra ligands are shown to be suitable materials for colorimetric volatile organic compound detectors. However, porphyrins that already have bound axial ligands when synthesized only show a sensor response to those analytes that can substitute these axial ligands. The Co porphyrin displays a considerably larger response than the other porphyrins investigated which is attributed to a switch between Co(II) and Co(III) resulting in a large spectral change.

Impact of variation in limb shape on sub-bandage interface pressure

BACKGROUND

Sub-bandage interface pressure generated by medical compression bandages (MCB) and hosiery changes in mobile patients as they move due to the change in the limb size. However, the amount of variation in the interface pressure is dependent on the stiffness of the compression material. Researchers have proposed several indices to describe this change in interface pressure, including the static stiffness index (SSI) and the dynamic stiffness index (DSI). These indices can also be used to classify compression products.

OBJECTIVES

To explore the different proposed indices to describe the stiffness of a compression material and compare it to the engineering stress-strain modulus which is used for the same purpose; To estimate theoretically the change in the interface pressure which is caused by the change in the limb shape as a consequence of calf muscle activity and the associated transient variation in limb dimensions.

METHOD

Use Chord modulus to classify compression material; Use thin and thick cylinder wall theory to estimate the variation in the interface pressure due to changes in the limb shape secondary to muscle contraction; Use tensile test devices to obtain the Chord modulus for two different MCB at two different dynamic ranges.

RESULTS

Chord modulus (E) describes the change in tension in a dynamic situation, and this is labelled as stiffness in the bandaging literature; Chord modulus, with the help of a mathematical model that was developed based on thick wall cylinder theory, can be used to predict the change in sub-bandage interface pressure caused by the change in limb shape secondary to calf muscle activity; Chord modulus can be used to classify bandages and describe how they will behave when they are applied to a leg.

CONCLUSION

The dynamic pressure can be predicted using a simple mathematical model using Chord modulus, which can be calculated in vitro using standard tensile testing equipment. In addition, Chord modulus can be used to classify compression bandages and hosiery.

Clinical outcomes and fusion success associated with the use of BoneSave in spinal surgery

BACKGROUND

Achieving spinal fusion is the guiding principle behind surgical treatment for a range of spinal pathologies, often requiring a substantial amount of bone-graft. Iliac crest autograft represents the gold standard although associated morbidities and limited graft material have led to the development of alternatives. BoneSave (Stryker, UK), a porous tricalcium phosphate-hydroxyapatite ceramic, is one such alternative, employed in spinal fusion over the past few years. Very little research exists into the clinical outcomes associated with its use.

METHODS

Clinical data was collected retrospectively from the case notes of 45 patients who underwent posterolateral inter-transverse spinal fusion involving the application of BoneSave between June 2003 and January 2005. Latest follow-up information was collected via a postal questionnaire (average follow-up of 46 months). Validated outcome instruments employed included the Short Form 36 and Oswestry Disability Index. In addition visual analogue scales for pain, patient global impression of change, work status, persisting symptoms and patient satisfaction data were collected. Radiological evaluation of fusion was carried out from the most recent spinal radiographs available for each patient.

RESULTS

Qualitative post-operative data was available in 96%, with a questionnaire response rate of 68.4%. Radiographical evaluation was possible in 67%. Significant post-operative improvements were seen across all outcome measures in the large majority of cases. Successful fusion was achieved in 56.7% of cases.

CONCLUSIONS

The clinical outcomes associated with the use of BoneSave in spinal fusion are comparable to those available in the literature for more conventional techniques. The fusion rate was not significantly lower.

Assessing patient readiness for the clinical adoption of personalized medicine

BACKGROUND/AIMS

Although pharmacogenomics-based diagnostics and therapeutics are increasingly being translated into personalized medicine applications, relatively little evidence exists about how novel pharmacogenomics-based technologies will be accepted and adopted by patients. It is important to understand the characteristics of genomic diagnostics and targeted therapeutics that might impact utilization or serve as barriers to adoption of these novel technologies in order to formulate appropriate policies and procedures. The objective of this study was to investigate patients' understanding and knowledge of personalized medicine and the process of decision-making regarding pharmacogenomics testing and targeted therapeutics and to better understand how patients value receiving pharmacogenomics-based care.

METHODS

We conducted 4 focus groups with 8-10 individuals in each group with patients recruited from out-patient clinics at The Methodist Hospital in Houston, Tex., USA.

RESULTS

The use of genomic diagnostics and targeted therapeutics to facilitate personalized medicine has considerable support from patients. However, our data revealed that participants were concerned with issues surrounding privacy and confidentiality of genetic test results, particularly with respect to access of information by insurers, with potential costs of testing and issues related to accuracy of test results. Questions regarding willingness to pay revealed that patients would be more willing to pay out-of-pocket if the disease associated with pharmacogenomic testing for treatment was perceived to be high risk (e.g., colorectal cancer) versus a chronic condition that was perceived as lower risk (e.g., high cholesterol).

CONCLUSION

As the personalized medicine approach is increasingly incorporated into health care, understanding patients' needs and their readiness to adopt these novel technologies will become progressively more important for the development of appropriate health policies.

Synthesis and characterization of ultra-small superparamagnetic iron oxide nanoparticles thinly coated with silica

Ultra-small superparamagnetic iron oxide nanoparticles (SPIOs) were synthesized by co-precipitation of iron chloride salts with ammonia and then encapsulated with thin (~2nm) layers of silica. The particles have been characterized for size, diffraction pattern, surface charge, and magnetic properties. This rapid and economical synthesis has a number of industrial applications; however, the silica-coated particles have been optimized for use in medical applications as MR contrast agents, biosensors, DNA capturing, bioseparation and enzyme immobilization.

Poor outcome in adolescents with high-risk Hodgkin lymphoma

This retrospective study looks at the differences between adolescents (15-19 years) and young adults (20-25 years), diagnosed with Hodgkin lymphoma and treated at the same adult institution. Outcome according to risk category was evaluated, and although there were no significant differences in the whole cohort, or low and intermediate-risk categories, high-risk adolescent patients had a significantly worse outcome compared to that of young adults. In these high-risk patients, 5-year event free survival was 43.6% in adolescents compared to 58.7% in young adults (log-rank survival p=0.03), and the 5-year overall survival in adolescents was 66.7% compared to 84.4% in the young adults (p=0.04). Possible contributing factors to this inferior outcome in these high-risk patients were explored. The difference could not be explained in terms of differences in histological subtype (p=0.5), proportion of patients with bulky (p=0.6) or extranodal disease (p=0.6), initial treatment received (chemotherapy alone compared to combination therapy, p=0.2), or proportion proceeding to high-dose treatment after initial treatment failure (p=0.6). There was no difference in the documented number of delays, dose reductions or episodes of non-compliance during initial treatment in the two high-risk age groups. A significantly greater proportion of high-risk adolescents had primary progressive disease (PPD) [eight high-risk adolescents (33.3%) compared to two high-risk young adults (7.7%), p=0.02].

The clinical and cost-effectiveness of left ventricular assist devices for end-stage heart failure: a systematic review and economic evaluation

OBJECTIVES

To assess the clinical and cost-effectiveness of left ventricular assist devices (LVADs) as a bridge to heart transplantation (BTT), as a bridge to myocardial recovery (BTR) or as a long-term chronic support (LTCS) for people with end-stage heart failure (ESHF).

DATA SOURCES

For the systematic review, electronic databases and bibliographies of related publications plus experts and manufacturers. For the economic evaluations, data originated from the systematic review of clinical and cost-effectiveness, UK hospitals, device manufacturers and expert opinion.

REVIEW METHODS

For the systematic review, studies were selected and assessed against a set of rigorous criteria; data were then synthesised using a narrative approach through subgroup analysis based on the indication for treatment, type of LVAD and quality of studies. The economic evaluation developed two models to evaluate the use of LVADs, first as a BTT and second as LTCS for patients suffering from ESHF.

RESULTS

Sixteen studies assessed the clinical effectiveness of LVADs as a BTT. Despite the poor methodological quality of the evidence, LVADs appeared beneficial compared to other treatment options (i.e. inotropic agents or usual care) or to no care (i.e. the natural history of ESHF) improving the survival of people with ESHF during the period of support and following heart transplantation. Patients supported by an LVAD appeared to have an improved functional status compared with those on usual care and experienced an improvement in their quality of life from before device implantation to the period during support. Serious adverse events are a risk for patients with an LVAD. With a scarcity of evidence directly comparing different devices, it is difficult to identify specific devices as the most clinically effective. The HeartMate LVAD is the only device that has evidence comparing it with the different alternatives, appearing to be more clinically effective than inotropic agents and usual care and as clinically effective as the Novacor device. Second generation devices, such as Jarvik 2000 and MicroMed Debakey LVADs, are early in their development but show considerable promise that should be assessed through long-term studies. Evidence of the clinical effectiveness of LVADs as a BTR was limited to seven non-comparative observational studies that appeared to show that the LVADs were beneficial in providing support until myocardial recovery. It was not possible to assess whether the LVADs are more effective than other alternatives or specific devices. No evidence was found on the quality of life or functional status of patients and limited information on adverse events was reported. Six studies assessed the clinical effectiveness of LVADs as an LTCS and from these it was evident that LVADs provided benefits in terms of improved survival, functional status and quality of life. Nineteen studies assessed the costs and cost-effectiveness of LVADS for people with ESHF, with the majority being simple costing studies and very few studies of the cost-effectiveness of LVADs. With no relevant cost-effectiveness studies available, an economic evaluation for BTT and LTCS was developed. The economic evaluation has shown that neither LVAD indication considered, that is, BTT and LTCS, is a cost-effective use. For the HeartMate LVAD used as a BTT the cost per QALY was pound 65,242. In the less restrictive indication, LTCS, where LVADs are not just given to patients awaiting transplantation, the analysis has shown that LTCS is not cost-effective. The baseline cost per QALY of the first-generation HeartMate LVAD was pound 170,616. One- and multi-way sensitivity analysis had limited effect on the cost per QALY. A hypothetical scenario based on the cost of a second-generation MicroMed DeBakey device illustrated that a 60% improvement in survival over first-generation devices was necessary before the incremental cost-effectiveness approached pound 40,000 per QALY.

CONCLUSIONS

Although the review showed that LVADs are clinically effective as a BTT with ESHF, the economic evaluation indicated that they are not cost-effective. With the limited and declining availability of donor hearts for transplantation, it appears that the future of the technology is in its use as an LTCS. Further research is needed to examine the clinical effectiveness of LVADs for people with ESHF, assessing patient survival, functional ability, quality of life and adverse events. Evaluations of the clinical effectiveness of LVADs should include economic evaluations, as well as data on quality of life, utilities, resources and costs. A systematic review of the epidemiology of ESHF should be undertaken to assess its potential impact.

Guidelines for clinical studies with compression devices in patients with venous disorders of the lower limb

OBJECTIVES

The scientific quality of published clinical trials is generally poor in studies where compression devices have been assessed in the management of venous disease. The authors' aim was to establish a set of guidelines which could be used in the design of future clinical trials of compression treatments for venous diseases.

DESIGN

Consensus conference leading to a consensus statement.

METHODS

The authors form a expert consensus group known as the International Compression Club (ICC). This group obtained published medical literature in the field of compression treatment in venous disease by searching medical literature databases. The literature was studied by the group which attended a consensus meeting. A draft document was circulated to ICC members and revised until agreement between contributors was reached.

RESULTS

The authors have prepared a set of guidelines which should be given consideration when conducting studies to assess the efficacy of compression in venous disease.

CONCLUSIONS

The form of compression therapy including the comparators used in the clinical study must be clearly characterised. In future studies the characteristics of the material provided by the manufacturer should be described including in vivo data on pressure and stiffness of the final compression system. The pressure exerted on the distal lower leg should be stated in mmHg and the method of pressure determination must be quoted.

The quest for Factor VIIa exosite inhibitors

Coagulation proteases are involved in a highly orchestrated proteolytic cascade which is essential for haemostasis and blood clotting. In particular, the initiator of the coagulation cascade, Factor VIIa, binds to its cofactor, tissue factor, and its substrate, Factor X, via exosite interactions to form a ternary catalytic complex named extrinsic Xase. These exosite interactions have also been shown to allosterically induce the active conformation of the catalytic site of Factor VIIa. We have developed a direct continuous fluorescence polarization-based extrinsic Xase assay, which has been used to screen in excess of 1 million structurally diverse low-molecular-mass compounds as a potential starting point for the development of anticoagulants. The primary screen hits were categorized with deconvolution assays into either active-site or exosite inhibitors. The latter category of hits displayed both competitive and uncompetitive modalities of inhibition with respect to Factor X activation. An uncompetitive mechanism of action is of particular interest as it offers a hypothetical inhibitory advantage in the context of inhibiting a proteolytic cascade such as the blood coagulation pathway.

Prenatal predictors of mortality in very preterm infants cared for in the Australian and New Zealand Neonatal Network

AIM

To identify antenatal and perinatal risk factors for in-hospital mortality of babies born within the Australian and New Zealand Neonatal Network (ANZNN).

METHODS

Data were collected prospectively as part of the ongoing audit of high-risk infants (birth weight <1500 g or gestation <32 weeks) admitted to all level III neonatal units in Australia and New Zealand. Antenatal and intrapartum factors to 1 min of age were examined in 11 498 infants with gestational age >24 weeks. Risk and protective factors for mortality were derived from logistic regression models fitted to 1998-9 data and validated on 2000-1 data.

RESULTS

For the whole cohort of infants born between 1998 and 2001, prematurity was the dominant risk factor, infants born at 25 weeks having 32 times greater odds of death than infants born at 31 weeks. Low birth weight for gestational age also had a dose-response effect: the more growth restricted the infant the greater the risk of mortality; infants below the 3rd centile had eight times greater odds of death than those between the 25th and 75th centiles. Male sex was also a significant risk factor (odds ratio (OR) 1.55, 95% confidence interval (CI) 1.31 to 1.82). Maternal hypertension in pregnancy was protective (OR 0.46, 95% CI 0.36 to 0.50). The predictive model for mortality had an area under the receiver operating characteristic curve of 0.82.

CONCLUSIONS

Risk of mortality can be predicted with good accuracy with factors up to the 1 min Apgar score. By using gestation rather than birth weight as the main indicator of maturity, these data confirm that weight for gestational age is an independent risk factor for mortality.