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Biomedical subjects

R S Ward

Publications and source records attributed to R S Ward.

At least 19 recordsLinked to original sources
PubMed2003

The natural (baseline) quality of groundwater: a UK pilot study.

Knowledge of the natural baseline quality of groundwaters is an essential prerequisite for understanding pollution and for imposing regulatory limits. The natural baseline of groundwaters may show a range of concentrations depending on aquifer mineralogy, facies changes, flow paths and residence time. The geochemical controls on natural concentrations are discussed and an approach to defining baseline concentrations using geochemical and statistical tools is proposed. The approach is illustrated using a flowline from the Chalk aquifer in Berkshire, UK where aerobic and anaerobic sections of the aquifer are separately considered. The baseline concentrations for some elements are close to atmospheric values whereas others evolve through time-dependent water-rock interaction. Certain solutes (K, NH(4)(+)), often considered contaminants, reach naturally high concentrations due to geochemical controls; transition metal concentrations are generally low, although their concentrations may be modified by redox controls. It is recommended that the baseline approach be incorporated into future management strategies, notably monitoring.

Journal Article↗
PubMed1999

Calibration of the Periotron 8000 and 6000 by polynomial regression.

This paper reports the detailed calibration of the new Periotron 8000 with different fluids and uses the method of least squares to derive polynomial regression equations up to the 6th order, to investigate the most accurate descriptor of the resulting calibration lines. The use of a 4th order polynomial regression equation (recommended by the manufacturer) provided better coefficients of determination (R2: 0.999) and root mean square errors (RMSE = 1.6) than either linear regression (R2: 0.986, RMSE = 10.9) or quadratic models (R2: 0.998, RMSE = 3.2). Data derived using the manufacturer's MLCONVERT software program lacked accuracy and incurred large errors for volumes > 0.5 microliter. Calibrations performed on one day could be used with accuracy to derive volumes > 0.1 microliter collected on subsequent days, when using the same machine (s.d. for residuals plot = 2.49 Periotron units), but this was not the case for different machines (s.d. = 9.57 Periotron units). Varying serum protein concentration by up to 500% had a negligible effect on calculated volumes above 0.1 microliter. We conclude that the Periotron 8000 is at least as reliable a machine as the Periotron 6000, and that the calibration lines for both machines are best described using 4th order polynomial regression equations and "look-up" tables, rather than quadratic (Periotron 6000) or the manufacturer's software (Periotron 8000). Serum seems to be an acceptable GCF substitute for calibrations, which can be performed 1 day, and used on subsequent days for a given machine and for volumes above 0.1 microliter.

Calibration↗
PubMed1995

Topical agents in burn and wound care.

With any open wound infection may occur. Many factors such as age and general health status may increase the likelihood of infection, but the size and depth of the wound are critical factors in determining the chronicity of any wound. Infection greatly adds to the morbidity associated with open wounds. An infected wound not only heals more slowly, there is also the risk of systemic infection and even death. Infected wounds also scar more severely and are associated with more prolonged rehabilitation. Topical therapeutic agents have been shown to be effective in the management of open skin wounds. These agents may assist less complicated healing and decrease the conversion of a partial-thickness injury to a full-thickness injury, and thereby reduce wound-related morbidity. Common topical agents with suggestions for application are discussed in this review.

Administration, Topical↗
PubMed1992

Influence of pressure supports on joint range of motion.

Burn patients often complain of restricted mobility following application of elasticized nylon anti-burn-scar supports. This study was designed to analyse the influence of this type of pressure garment on joint range of motion (ROM). Data were compiled from 80 burn-affected joints of 17 burn patients placed in a support for the first time. Joint ROM was measured directly prior to, and again immediately following, the donning of the pressure support. ROM was measured using standard goniometric techniques. Range of motion increased in 26 joints (32.5 per cent), decreased in 26 joints (32.5 per cent) and showed no change in 28 joints (35 per cent) after application of the pressure garment. There were no correlations between ROM results and age, time postburn and per cent TBSA in this population. Patients were also asked if movement felt any different after the support was applied. Their varied comments, such as movement felt easier or more difficult, were consistent with the actual ROM data. It appears that there is no predictably detrimental change in joint ROM due to the application of pressure garments.

Adult↗
PubMed1990

Rehabilitation of burn patients with concomitant limb amputation: case reports.

Burn patients with associated limb amputations present demanding rehabilitation problems, many of which might be expected to lead to chronic difficulties. Therapeutic goals following limb amputation include oedema reduction, prevention of contracture (through positioning and range of motion), stump shaping, both pre- and post-prosthetic fitting strengthening exercises of the limb and trunk, and gait training. Some patients present problems that are associated with both the burn injury and the limb amputation that cause concern among the physical therapy staff. Some of these situations include intolerance of the stump to pressure or manipulation due to remaining open wounds or fragility of newly skin grafted areas on the residual limb or delayed gait or functional training due to wounds on other body surface areas. Delays in stump preparation or other treatment aims due to continued surgical procedures can be worrisome. A review of these patients indicates the possible difficulties that rehabilitation personnel may face when treating burn victims who required amputation. Effective rehabilitation of these patients can be achieved despite the noted concerns.

Adult↗
PubMed1989

A comparison of two crisis housing alternatives to psychiatric hospitalization.

This study compared outcomes for demographically matched clients four months after their admission to two short-term crisis programs. The programs provided crisis housing and case management services as alternatives to psychiatric hospitalization for clients with severe and persistent mental illness. One program met housing needs by purchasing shelter in hotels and boarding houses, and the other provided lodging in an eight-bed crisis house. In both programs, two-thirds of the clients avoided hospitalization during four-month follow-up, and both programs were effective in stabilizing clients' housing and financial situations. Clients in the purchase-of-housing program showed an increase in substance abuse problems at follow-up. Average client costs were similar in the two programs. A critical program difference was the substantially higher staff turnover in the crisis house, which was later replaced with scattered-site crisis housing.

Adult↗
PubMed1988

Assertive case management in three CMHCs: a controlled study.

At three community mental health centers (CMHCs) in Indiana, 167 clients at risk for rehospitalization were randomly assigned to experimental groups receiving assertive case management (ACM) or to control groups eligible to receive all other aftercare services at the centers. During a six-month follow-up period, experimental clients received an average of one visit a week from the ACM team, usually in the client's home or in community settings. Overall, ACM clients were rehospitalized an average of 9.2 days, significantly less than the 30.8 days for controls. In two of the three centers, significant rehospitalization differences were also found between ACM and control groups. No differences were found between groups in quality of life, medication compliance, involvement in CMHC programs, or contacts with the legal system in any of the centers. The most cost-effective center had savings of about +5,500 for each ACM client.

Adult↗
PubMed1988

In vivo evaluations of a new thromboresistant polyurethane for artificial heart blood pumps.

To reduce the risk of thromboembolic complications in prosthetic blood pumps, we have developed a new segmented polyurethane elastomer. This material is unique because its mechanical properties for long-term durability and surface properties for biocompatibility have been separated and developed in two distinct materials. Improved thromboresistance is then obtained by a 1% concentration of a new polymeric surface-modifying additive blended with the base polyurethane before fabrication of the blood pump. To evaluate this material in vivo, we performed 10 implants, in calves, of the Pierce-Donachy prosthetic ventricle with blood-pumping sacs and cannulas fabricated from the new surface-modifying additive copolymer blend (Thoratec's BPS-215M). In four control implants the blood sacs and cannulas were fabricated from Ethicon's Biomer segmented polyurethane, which is the present clinical standard for most artificial hearts and circulatory support devices. The blood pumps were connected from the apex of the left ventricle to the descending aorta in male Holstein calves weighing 82 to 108 kg and were driven pneumatically in the full-to-empty mode with flows averaging 5 to 6 L/min. Each calf was medicated with aspirin and dipyridamole throughout the study period and was electively put to death after 4 weeks for evaluation of explanted blood sacs and for examination of the kidneys for infarction. All 10 explanted blood sacs made with the surface-modifying additive copolymer blend were shiny and completely free of thrombus. Three of the four explanted Biomer blood sacs showed visible red thrombus, and all four showed small areas of white thrombus. The average surface area of the Biomer blood sacs covered with thrombus was 45 +/- 32 mm2. Use of a semiquantitative scale to assess renal infarction demonstrated that nine of 10 animals with a surface-modifying additive copolymer blend blood sac had infarction less severe than the mean infarct score of the animals with a Biomer sac. The surface-modifying additive copolymer blend has excellent mechanical and physical properties necessary for use in artificial heart blood pumps. From these experiments, we conclude that the surface-modified polyurethane blend is superior to Biomer polyurethane in blood compatibility and in freedom from thromboembolic risk. This material is now approved by the Food and Drug Administration for investigational device exemption studies in the Pierce-Donachy prosthetic ventricle.

Animals↗
PubMed1981

Development of a silica-free silicone system for medical applications.

Filler-free silicones are believed to be more blood-compatible than those containing fillers. An ultrapure silica-free room temperature vulcanizing silicone system was prepared and characterized using a swelling experiment, an infrared spectrometer, an x-ray spectrometer, a scanning electron microscope and neutron activation analysis. The polymer was found to be suitable for medical applications needing an extremely smooth surface.

Biocompatible Materials↗
PubMed1977

Development of blood-compatible elastomers. V. Surface structure and blood compatibility of avcothane elastomers.

The Avcothane 51 elastomer, a member of a series of proprietary materials best characterized as polyurethane/poly(dialkylsiloxane) block copolymers, displays considerable hemocompatibility without any incorporated anticoagulants. In the form of intra-aortic balloons, the elastomer was implanted in several thousands of cardiac patients without intolerable hematologic effects. Hemocompatibility has been assumed to result from a predominantly dispersion-type surface force field whose intensity fluctuates within small domains, maintaning adsorbed blood proteins in an unstable state. The relative hemocompatibility of films, which were obtained from a prepolymer solution cast on substrates impenetrable to the solvent, is a function of the effective surface molecular structure. This can vary as a function of preparative conditions (temperature and rate of evaporation), and has been correlated with an anisotropic distribution of the silicone component in cured films. The concentration of this component in surface layers was quantified independently by IRATR spectroscopy and electron-microprobe analysis, giving consistent results. An IRATR index, which is computed from the ratio of absorptivities measured at 13.00 and 12.62 mu and is inversely proportional to the relative silicone content of surface layers, was found to correlate with the apparent hemocompatibility determined by different in vitro methods. Optimized reproducible hemocompatibility is attained by strict process controls.

Assisted Circulation↗