The use of colloid probe microscopy to predict aerosolization performance in dry powder inhalers: AFM and in vitro correlation

The atomic force microscope (AFM) colloid probe technique was utilized to measure cohesion forces (separation energy) between three drug systems as a function of relative humidity (RH). The subsequent data was correlated with in vitro aerosolization data collected over the same RH range. Three drug-only systems were chosen for study; salbutamol sulphate (SS), triamcinolone acetonide (TAA), and di-sodium cromoglycate (DSCG). Analysis of the AFM and in vitro data suggested good correlations, with the separation energy being related inversely to the aerosolization performance (measured as fine particle fraction, FPF(LD)). In addition, the relationship between, cohesion, RH, and aerosolization performance was drug specific. For example, an increase in RH between 15% and 75% resulted in increased cohesion and decreased FPF(LD) for SS and DSCG. In comparison, for TAA, a decrease in cohesion and increased FPF(LD) was observed when RH was increased (15-75%). Linear regression analysis comparing AFM with in vitro data indicated R(2) values > 0.80, for all data sets, suggesting the AFM could be used to indicate in vitro aerosolization performance.

Evaluation of a new composite dressing for the management of chronic leg ulcer wounds

OBJECTIVES

A new composite dressing (Versiva, ConvaTec) combines three technologies: hydrocolloid, hydrofibre and a foam-film layer. This study aimed to assess the safety of the dressing in the management of patients with venous leg ulcers. Clinical performance was also assessed.

METHOD

This multicentre, non-randomised, open-label, phase II study assessed the safety (via adverse-effect reporting) and performance, including weartime, absorption, dressing integrity, ease of use and wound progression, of Versiva. Up to 10 dressing changes were assessed within a five-week study period.

RESULTS

In 75 dressing changes of 11 ulcers, the mean wear time was approximately five days. No or minimal leakage was observed in 81% of changes. In 93%, the dressing was 'very easy' to remove, with no trauma to surrounding skin. Most changes (77%) were painless.

CONCLUSION

Versiva met or exceeded the investigators' expectations for exudate absorption, protection of peri-wound skin and reduction in wound pain and ulcer area. Healing or marked improvement was observed in 82% of leg ulcers within the five-week study. The relatively long wear-time of five days represents a cost-effective advantage for this dressing compared with other available adhesive foams for the management of chronic wounds.

Controlled, randomized clinical trial of 2 hydrocolloid dressings in the management of venous insufficiency ulcers

A prospective, randomized study was conducted to compare the performance of 2 hydrocolloid dressings, hydrocolloid A and hydrocolloid B, in the treatment of venous insufficiency ulcers. A total of 31 patients were enrolled at 2 clinical sites. Complete wound closure (100% epithelialization) was observed in 59% of the patients treated with hydrocolloid A, compared with complete wound closure in 15% of the patients in the hydrocolloid B group (P <or=.03). Investigators also rated hydrocolloid A significantly better in ease of application, adhesion, conformability, exudate absorption, barrier properties, transparency, and patient comfort (P <or=.02). Significantly fewer patients in the hydrocolloid A group required unscheduled, product-related dressing changes (P <or=.02). In this clinical study, hydrocolloid A demonstrated excellent performance characteristics and was highly effective in treating venous insufficiency ulcers.

The influence of four wound dressings on the kinetics of human walking

OBJECTIVES

This in vivo study (the second phase of a research project first described in the February issue of Journal of Wound Care) reports on the influence of various wound dressings on the dynamics of human walking. Allevyn (Smith and Nephew), Biatain (Coloplast), Lyofoam (Seton Scholl) and Tielle (Johnson and Johnson) were used in this study. The investigation aimed to assess the ground reaction forces in the foot while the dressings were applied to the plantar surface of the foot.

METHOD

A strain gauge force plate system was used. Six subjects with 'normal' gait patterns and no foot pathology were recruited into the study. Eight trials were recorded for each subject. The peak push-off force, in the vertical component of the ground reaction force, and the maximum braking and propulsive forces in the medial-lateral component of the ground reaction force were estimated and reported.

RESULTS

Among the various dressings tested, Allevyn performed closest to barefoot in the peak push-off force and demonstrated an increased braking force at the deceleration point in the gait cycle.

CONCLUSION

These findings may have implications for clinicians selecting wound dressings for the treatment of certain foot ulcerations. However, further clinical research is warranted in this area.

An in-vitro study of the pressure-relieving properties of four wound dressings for foot ulcers

This in-vitro study reports on a selection of mechanical tests on four wound dressings: Allevyn (Smith and Nephew), Biatain (Coloplast), Lyofoam (Seton Scholl) and Tielle (Johnson and Johnson). The aim of the study was to investigate these dressings in the laboratory by subjecting them to dry and wet compression tests, shearing tests and a cyclical test. As predicted, all dressings performed differently in the range of tests, with Lyofoam deforming the most when subjected to compression testing (5.6 mm). During wet compression, differences in the physical properties of all the materials tested were identified. During shearing testin, Allevyn and Tielle withstood the greatest shear deflection before failure, but Biatain withstood the greatest force before failing. During the cyclical testing, Lyofoam only reduced by 1% of its original thickness, while Biatain reduced by 30%. No one dressing performed better in all the tests. However, as an all-round 'pressure-relieving' dressing, Allevyn consistently outperformed the others in the study.

Dressing selection for the treatment of coumarin necrosis

The correct dressing selection is of vital importance in producing as rapid a healing response as possible. John Timmons demonstrates the effects of a new dressing for the treatment of coumarin necrosis. Coloplast, the manufacturers of the dressing, Biatain Adhesive, supported the author while he was treating the patient.

The cleaning of polymer colloids

The current state of knowledge of the cleaning of polymer colloids is reviewed with regard to a wide range of cleaning and characterisation techniques. The type, level and quantity of impurities involved with different polymer latex formulations varies widely. Even for similar formulations, differences in the nature and number of functional groups reported are often a consequence of sometimes subtle differences in the cleaning procedures employed. Not only may surface functionality be affected but also monomer and oligomer extraction procedures may lead to morphological changes in the particles. No single technique alone is likely to be able to remove all impurities. Care is needed to avoid the introduction of new impurities from the equipment, materials and water used as well as possible contamination from atmospheric carbon dioxide, bacteria and fungi. These factors also need to be considered in the storage of latex particle standards.

A comparison of two dressings in pressure sore management

This study compared a polyurethane foam dressing with a hydrocolloid dressing for ease of application and removal, adhesion, conformability, absorbency and wear time. A randomised study was carried out, including 61 patients with stage two or three pressure sores in five centres in the UK. Dressings were applied for up to 30 days and assessments were carried out at each dressing change. The results indicated that both dressings are easy and convenient to apply; absorbency and ease of removal were significantly better with the polyurethane foam dressing than the hydrocolloid dressing; wear times were similar.

Evaluation: A study to compare two film dressings used as secondary dressings

Dressings manufactured from adhesive polymeric films have been used extensively in wound management for about 20 years. This report describes the results of a trial designed to compare the performance of two such dressings, used as secondary dressings, in a multi-centre randomised controlled community study involving 100 patients. Independent analysis of the study data revealed that, after adjusting for other effects, no genuine difference was demonstrated between the dressings in terms of their ability to resist wrinkling or prevent maceration (the primary outcome variable).

The cytocompatibility of hydrocolloid dressings

The purpose of this study was to evaluate the effect on fibroblast proliferation of hydrophilic particles isolated from six commercial hydrocolloid dressings. The hydrophobic adhesive matrix of six hydrocolloid dressings was removed using a reflux extraction method with an organic solvent (xylene). The remaining hydrophilic particles were dissolved in complete cell growth medium containing 10% (v/v) foetal calf serum and added to confluent human dermal fibroblasts grown in monolayer in final concentrations of 0.1 and 0.01% (w/v). Control cells received growth medium alone. The fibroblasts were incubated with the hydrophilic particles and the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU) for 24 hours. The incorporation of BrdU into DNA was used as a measure of cell proliferation and determined using an ELISA kit. The results were expressed in percentage of control-treated wells and analysed using analysis of variance. Apart from Comfeel Plus, the hydrophilic particles of hydrocolloid dressings significantly inhibited fibroblast proliferation at 0.1% compared to control-treated fibroblasts (p < 0.05).

Heel pressure relieving devices how effective are they?

This study of patients hospitalized for hip replacement or treatment of hip dislocation or fractured neck or shaft of the femur compared the efficacy of three approaches to the care of the patients' heels. A control group of 15 patients received routine nursing care and treatment groups of 15 and 20 patients received routine nursing care combined with the use of hydrocolloid dressing and eggcrate foam respectively. The combination of routine nursing care and the use of eggcrate foam was found to be more effective method of maintaining skin integrity than nursing care alone or nursing care combined with the use of hydrocolloid dressing. The study findings support the use of eggcrate foam as a heel pressure relieving device and it is recommended that its use is initiated from the time patients are admitted to hospital.

Tegasorb hydrocolloid dressing: advanced formulation

Tegasorb advanced formulation hydrocolloid dressing from 3M Healthcare can be used on a variety of wounds, e.g. leg ulcers and donor sites. It encourages a moist wound-healing environment and can be used in all stages of wound healing, from black necrotic tissue to the epithelializing wound. Tegasorb is a well-established hydrocolloid dressing that has recently been relaunched as an advanced formulation.

Evaluation of a hydrocolloid dressing

A hydrocolloid dressing was compared to adhesive skin tapes on children's postoperative wounds. A total of 170 children of varying ages were randomised in two parallel groups, in nine centres of plastic, thoracic, gastrointestinal, urogenital and orthopaedic surgery. Skin closure was satisfactory in both groups, with 76 (89.4%) healthy closures without dehiscence in the hydrocolloid group and 81 (95.3%) in the control group; a relationship was found between partial closures/dehiscence and the type of surgical procedure. No product-related maceration, infection or adverse event was reported during the study and both groups showed very satisfactory cosmetic results.

31P NMR spectroscopic analysis of wound healing: the effect of hydrocolloid therapy

With the advent of managed care, wound care professionals have limited time to heal chronic wounds. They need to know whether the repair process is progressing or stagnating in response to treatments. Phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopic measurements of chronic wound biochemistry yields rapid knowledge of whether a wound is generating, storing, or using energy. We used 31P NMR analysis on biopsy samples to explore the energy status of two chronic non-healing leg ulcers, before and after the first week of treatment with two low-pH hydrocolloid materials. Energy generation (i.e., energy "charge") was initially low in both wounds and was significantly elevated after 1 week of treatment. Earlier work has shown that leg ulcer pathophysiology is altered during the first week of hydrocolloid treatment. This work traces the origins of such effects deeper into the cellular biochemistry and correlates the measures with the final healing outcome. 31P NMR spectroscopy may provide a real-time biochemical "fingerprint" that shows clinicians the healing status of a questionable wound. Further study is needed to confirm the reliability and validity of 31P NMR spectroscopy as a predictor of healing outcomes in other wound environments.

In vitro assessment of water vapour transmission of synthetic wound dressings

The water vapour transmission rate (WVTR) of 14 commercially available wound dressings (11 hydrocolloids, 2 hydrogels and 1 polyurethane film) was evaluated over 24 and 48 h periods using a modified ASTM standard method (ASTM E96-90). For the 48 h studies a novel microcomputer-controlled apparatus was employed. The dressings exhibited a wide range of WVTRs (76-9360 g m-2 d-1 at 24 h under forced air convection of 0.4 m s-1). The influence of air velocity of 0.4 m s-1 was not significant if the WVTR of the dressing was less than 880 g m-2 d-1 when measured under static air conditions. The influence of outer barrier layers and additional bandages on WVTR was also examined.

A comparative study of wound dressings on full-thickness wounds in micropigs

Eight full-thickness (to the depth of adipose tissue) skin wounds were surgically inscribed on the backs of four Yucatan micropigs (32 wound sites in total). Wound sites were created to allow for controlled comparative evaluation between wound sites, wound dressings, and specified postoperative healing time. The wounds were dressed with either ClearSite hydrogel dressing (New Dimensions in Medicine, Dayton, Ohio) or Duoderm hydrocolloid wound dressing (ConvaTec Inc., Princeton, New Jersey). Tracings and photographs of each wound site were made and computerized planimetry was done to compare the rate of epithelialization for like wounds and like wound dressings. Histomorphometric measurements were also made to compare the effects of the dressing on the wounds at the cellular level. The results of this study indicate that the wounds covered with the hydrogel dressing exhibited a more rapid rate of closure and reepithelialization as compared with the hydrocolloid wound dressing.

A comparison of the efficacy and cost-effectiveness of two methods of managing pressure ulcers

To compare the efficacy and the cost-effectiveness of moist gauze dressings and a hydrocolloid wafer dressing (DuoDERM CGF), 70 patients with 97 pressure ulcers that were stage II and/or stage III were randomly assigned to one of two treatment methods: moist gauze dressings or hydrocolloid dressings. Efficacy was defined as the number of ulcers that completely healed. In this debilitated, poorly nourished group of patients, one ulcer completely healed in the moist gauze dressing group, and 11 healed in the hydrocolloid group. The per diem cost of the moist gauze dressing was $12.26; the per diem cost of the hydrocolloid dressing was $3.55.

Role of hydrocolloids in wound management

This article describes the actions of hydrocolloid dressings and the type of wounds for which they are most suitable. The range of hydrocolloid products is reviewed along with their individual advantages and disadvantages.

Clinical benefit of a hydrocolloid dressing in closed surgical wounds

A prospective, multicenter trial evaluated the clinical benefits of a new hydrocolloid wound dressing material (DuoDERM Extrathin; ConvaTec International, Skillman, N.J.) in a postoperative setting. Criteria assessed were patient quality of life (adherence of the dressing, showering or bathing possibilities, aspects of dressing changes), safety (incidence of infection), effectiveness (healing time), and clinical utility (ease of application and removal, ease of inspecting the wound through the dressing). Ninety-five patients with 102 sutured wounds were enrolled in the study during a period of 18 months. Forty-three wounds were in anatomic areas considered difficult to dress with such conventional materials as gauze and tape. The overall incidence of infection was 2%; the dressing was found not to be a causal factor. In five wounds, treatment had to be stopped before scheduled. Comfort rating by the patients and the investigators were "good" and "very good" in 95% and 92% of cases, respectively. A mean of 1.56 dressings per wound was used until removal of the sutures. Because of the reduction in the necessary number of dressing changes, hydrocolloid dressing may help in reducing treatment costs.

Autocorrelation spectroscopy for particle sizing and stability tests of radiolabelled colloids

In many nuclear medicine applications a well defined particle size and stability of administered colloids is of great importance. A fast and reliable sizing technique for routine quality control is therefore essential. This paper evaluates autocorrelation spectroscopy with an instrument capable of analysing several peaks simultaneously. A total of nine 99mTc-labelled colloids and one 99Y-labelled colloid were studied. The autocorrelation spectroscopy measurements were compared with the standard sizing technique of microfiltration. A good agreement between the sizing techniques was found for most of the colloids. The reproducibility of successive measurements was within +/- 12% and +/- 40% when using unimodal analysis and SDP analysis, respectively. Autocorrelation spectroscopy was found to be well suited for particle sizing and stability tests of radiolabelled colloids.

Accuracy of casts produced from alginate and hydrocolloid impression materials

It is recognized that alginate impression materials have been used to obtain casts from which castings have been fabricated for a number of years. This study indicates that more dimensionally accurate casts are produced from hydrocolloid compared with casts produced from alginate. The most accurate casts were produced from the polyether impression material.

Vial retention of technetium-99m sulfur colloid in commercial kits

Vial retention of technetium-99m sulfur colloid in five commercial kits used for the preparation of this radiopharmaceutical was studied. Radiochromatography and microscopic particle sizing were performed on all products; the biologic distribution in rats of two products was tested. Loss of activity attributable to vial retention was evident with only two products. The resulting loss of specific concentration did not affect biologic distribution. The cause of the "plating-out" of the radiopharmaceutical on the interior reaction vial surface was not determined, although the gelatin component of the product was suspected to be a factor.

Effect of viscosity on the accuracy and stability of elastic impression material

A ram and cylinder penetrometer was designed to measure the viscosity of impression materials at their time of placement. Viscosity had no effect on accuracy or stability of the impression materials within the viscosity ranges studied.