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Biomedical subjects

William A Smith

Publications and source records attributed to William A Smith.

At least 19 recordsLinked to original sources
PubMed2006

Isolation and characterization of Cr(VI) reducing Cellulomonas spp. from subsurface soils: implications for long-term chromate reduction.

Microbial enrichments from Cr(VI) contaminated and uncontaminated US Department of Energy Hanford Site sediments produced Cr(VI) reducing consortia when grown in the presence of Cr(VI) with acetate, D-xylose or glycerol as a carbon and energy source. Eight of the nine isolates from the consortia were Gram positive and four of these were identified by 16S rRNA sequence homology and membrane fatty acid composition as belonging to the genus Cellulomonas. Two strains, ES6 and WS01, were further examined for their ability to reduce Cr(VI) under growth and non-growth conditions. During fermentative growth on D-xylose, ES6 and WS01 decreased aqueous Cr(VI) concentrations from 0.04 mM Cr(VI) to below the detection limit (0.002 mM Cr(VI)) in less than three days and retained their ability to reduce Cr(VI) even after four months of incubation. Washed ES6 and WS01 cells also reduced Cr(VI) under non-growth conditions for over four months, both with and without the presence of an exogenous electron donor. K-edge XANES spectroscopy confirmed the reduction of Cr(VI) to Cr(III). The ability to reduce Cr(VI) after growth had stopped and in the absence of an external electron donor, suggests that stimulation of these types of organisms may lead to effective long-term, in situ passive reactive barriers for Cr(VI) removal. Our results indicate that Cr(VI) reduction by indigenous Cellulomonas spp. may be a potential method of in situ bioremediation of Cr(VI) contaminated sediment and groundwater.

Cellulomonas↗
PubMed2006

Development and testing of portable pump for the induction of profound hypothermia in a Swine model of lethal vascular injuries.

UNLABELLED: Rapid induction of a profound hypothermic state (suspended animation) can maintain viability of key organs during repair of lethal injuries. Conventional cardiopulmonary bypass equipment (roller pump) used to induce and reverse hypothermia is expensive, bulky, requires standard electricity, and is not transportable. Development of a small, portable, battery operated, disposable, pump can logistically facilitate induction and maintenance of hypothermia. In this experiment, a portable prototype pump was tested and its performance was compared with the regular roller pump in a swine model of lethal vascular injuries. METHODS: Uncontrolled hemorrhage was induced in 16 swine (80-120 lbs) by creating an iliac artery and vein injury (nonlethal). After 30 minutes of pulseless shock, the descending thoracic aorta was lacerated (lethal injury). Through a left thoracotomy approach, a catheter was placed in the aorta and cold organ preservation solution was infused to rapidly (2 degrees C/min) induce hypothermia (10 degrees C) for 60 minutes. The performance of the prototype pump was initially tested in a nonsurvival experiment (four animals). Then, 12 animals were cooled either with (n = 6/group) (1) conventional roller pump or (2) small prototype pump. The injuries were repaired during hypothermic arrest and the animals were re-warmed (0.5 degrees C/min). Whole blood was infused during resuscitation on cardiopulmonary bypass. Surviving animals were closely monitored for 3 weeks for postoperative complications, neurologic deficits, and organ dysfunction. RESULTS: The flow rates and the time needed to induce and reverse profound hypothermia were no different between the prototype and the conventional roller pumps. Three-week survival rates were 83% in both groups. Only a transient increase in liver enzymes, and markers of cellular injury (creatine kinase, lactate dehydrogenase) was noted (no meaningful difference between groups), with no long-term organ dysfunction. CONCLUSIONS: In this large animal model of lethal vascular injuries, a portable, battery operated, disposable, rotary pump performed as well as the conventional roller pump. The logistical advantages of this system make it an attractive choice for inducing hypothermia in emergency departments and austere settings, and for maintaining hypothermia during transport.

Animals↗
PubMed2005

MagScrew total artificial heart in vivo performance above 200 beats per minute.

PURPOSE: Downsizing pulsatile devices requires an increase of beat rate if flow capacity is to be maintained. We applied this concept to the preclinical MagScrew total artificial heart (TAH). DESCRIPTION: The device fills passively with a stroke volume of 45 ml and beat rates up to 250 beats per minute (bpm). EVALUATION: Stable hemodynamics were observed during a 30-day bovine implant with a flow of 8.7 +/- 1.2 L/min at beat rates of 204 +/- 18 bpm. Device filling was exceptional up to 250 bpm generating flow of greater than 12 L/min. Beat rate adapted to preload in a way similar to a Frank-Starling response. Left and right atrial pressures were balanced. The aortic pulse pressure was 49-70 mm Hg, which translates to a pulsatility index of 0.49-0.77. Organ functions were preserved and blood damage did not occur. CONCLUSIONS: Increasing the beat rate while downsizing the MagScrew TAH was successful with strong flow generation by passive filling. Pulsatility was maintained at high beat rates. This innovative approach may be used to develop small pulsatile pumps.

Animals↗
PubMed2005

The PediPump: a new ventricular assist device for children.

Options for mechanical circulatory support for the treatment of end-stage heart failure in children are limited. Ventricular assist devices (VADs), which have revolutionized cardiac care in adults, remain largely unavailable for pediatric applications. The PediPump is a new rotary dynamic VAD designed to provide support for the entire range of patient sizes encountered in pediatrics. Despite being much smaller than currently available VADs, which makes it suitable for even newborn circulatory support, the PediPump demonstrates excellent hemodynamic performance.

Child↗
PubMed2005

A portable cardiopulmonary bypass/extracorporeal membrane oxygenation system for the induction and reversal of profound hypothermia: feasibility study in a Swine model of lethal injuries.

The Cleveland Clinic Foundation's (CCF) cardiopulmonary bypass/extracorporeal membrane oxygenation (CPB/ECMO) system capabilities were tested in a hypothermia trauma management feasibility study in a porcine animal model at the Uniformed Services University of the Health Sciences (USUHS, Bethesda, MD, U.S.A.). In this survival series, the CCF system was used in a simulated forward lines combat casualty application where lethal uncontrolled hemorrhage from major vascular injuries was repaired under a state of profound hypothermic arrest (suspended animation), followed by recovery and monitoring in an intensive care unit (ICU) setting. The animals were monitored for survival, neurological impact, cognitive functions, organ damage, and delayed complications over 3 weeks. A survival rate of 83% matched rates previously found using conventional equipment. Neurological findings, organ dysfunction, and complication rates also were no different from previous studies using standard equipment. Successful survival results demonstrated that the CCF CPB/ECMO system could be used to induce a period of profound hypothermic arrest for the repair of lethal traumatic injuries. The logistical advantages of this system make it an attractive choice for use in austere settings and during transport.

Animals↗
PubMed2004

Assessment of coronal microleakage of three materials used in endodontically treated teeth.

This study compared the coronal microleakage of three restorative materials used to seal the access cavity in root treated teeth. Thirty six teeth were prepared and three experimental groups were obturated and the access cavity filled with different materials; Group A--Intermediate Restorative Material, Group B--Fuji II and Group C--Dyract AP. Microleakage was assessed by Indian ink penetration. The mean coronal dye leakage for Group A was 0.895 mm, for Group B 1.914 mm and for Group C 3.245 mm. There was significantly (p < 0.05) more dye leakage in teeth restored with Dyract AP compared to those with Fuji II or IRM.

Analysis of Variance↗
PubMed2002

Overcoming barriers to reducing the burden of affective disorders.

Affective disorders impose a substantial individual and societal burden. Despite availability of efficacious treatments and practice guidelines, unmet need remains high. To reduce unmet need and the burden of affective disorders, information is needed on the distribution of burden across stakeholders, on barriers to reducing burden, and on interventions that effectively reduce burden at the levels of practice, community, and policy. This article provides the report of the Working Group on Overcoming Barriers to Reducing the Burden of Affective Disorders, for the National Institute of Mental Health Strategic Plan on Mood Disorders. We review the literature, identify key gaps, and recommend new research to guide national efforts to reduce the burden of affective disorders.

Community Health Services↗
PubMedDate not supplied

In vivo studies of the MagScrew total artificial heart in calves.

The purpose of this study was to evaluate the in vivo pump performance of our total artificial heart (TAH), the "MagScrew TAH." The TAH consists of a blood pump and control logic developed at the Cleveland Clinic and the MagScrew actuator and electronic control system developed by Foster-Miller Technologies, Inc. (Albany, NY). MagScrew TAH implantation was performed in two calves. Study durations were 50 and 5 days. The causes of termination were prosthetic valve endocarditis in one case and cable failure in the other. Mean left pump flow ranged from 8.0 to 9.7 L/min, with left atrial pressure of 3.0 to 16.0 mm Hg. Preload sensitivity of the MagScrew TAH demonstrated a Frank-Starling response to preload in automatic mode. The relationship between right and left atrial pressure was well balanced. Mean arterial pressure and mean pulmonary artery pressure were maintained within physiologic ranges over study duration. There were no signs of bleeding, hemolysis, or organ failure. The MagScrew TAH showed physiologic pump performance, and hemodynamics were well maintained without any organ failure. Further development testing will bring the MagScrew TAH to the point of preclinical readiness testing.

Animals↗
PubMedDate not supplied

Rotodynamic pump scaling.

Despite extensive theoretical knowledge of fluid dynamics, the design process for rotodynamic pumps still relies heavily on experimental data. One common technique is to model the design of a new pump based on the design of existing pumps, using the laws of similarity. Another, similar approach frequently used for atypically large or small pumps is to scale a final product design from conveniently sized laboratory prototypes that have been refined to the desired performance in extensive experiments. Both approaches to pump design are usually considered highly reliable. However, for blood pumps, this approach has been questioned. Due to the extremely small size of these pumps and the relatively low Reynolds Numbers, extraneous effects may overwhelm the assumptions made for similarity calculations that are satisfactory for significantly larger models. Three geometrically similar pumps with related scaling factors of 1, 3.2, and 6.4 were tested for the same range of nondimensional flow and pressure. The quality of similitude was determined by comparing the nondimensionalized pump data of the three pumps. It was found that the effects of large linear dimension scaling factors had only a small influence on the quality of similitude (maximum 5.8% error), whereas Reynolds Number effects, especially at high pump flows, had a strong impact on the quality of similitude (maximum 45.4% error). Because Reynolds Number similarity cannot always be achieved simultaneously with geometric similarity, a correction factor for Reynolds Number related departure from similarity was developed. It is based on the Reynolds Number, the Flow Coefficient, the specific speed, and the pump's relative surface roughness. Use of this correction factor reduces the error due to Reynolds Number effects to a maximum of 7.5%. We conclude that the use of scaling techniques in rotodynamic blood pump design is a valid approach, if Reynolds Number similarity is maintained or suitable correction factors are used.

Equipment Design↗
PubMedDate not supplied

In vitro controllability of the MagScrew total artificial heart system.

The purpose of this study was to evaluate the in vitro responses to preload and afterload of our total artificial heart (TAH), the MagScrew TAH. The TAH consists of two blood pumps and a control logic, developed at the Cleveland Clinic, OH, and the MagScrew actuator and its electronic control system, developed by Foster-Miller Technologies, Inc., Albany, NY. Tests were performed on a mock circulatory loop, using water as a test fluid. Preload sensitivity of the Mag-Screw TAH demonstrated a Frank-Starling response to preload in automatic mode. A peak flow of 10 L/min was obtained, with a left atrial pressure of 13 mm Hg. The relationship between right atrial pressure and left atrial pressure was well balanced when tested with a left bronchial shunt flow of 5% and a range of pulmonary artery and aortic pressures. With respect to afterload response, the left pump showed a relatively low sensitivity, which allowed the pump to maintain perfusion over a wide range of aortic pressures. The right pump, on the other hand, was much more sensitive to pulmonary artery pressure, which provided a measure of protection against pulmonary congestion. The very effective physiologic response of the MagScrew TAH is believed to result from employment of a left master, alternating ejection control logic, high inherent sensitivity of the blood pumps to atrial pressure, a lower effective stroke volume for the right pump, and a scaling of right side motor ejection voltage to 80% of that used for the left side ejection.

Aorta↗
PubMedDate not supplied

In vivo performance and biocompatibility of the MagScrew ventricular assist device.

Currently available ventricular assist devices (VADs) have limitations in long-term durability and blood compatibility. We evaluated a prototype of a pulsatile MagScrew VAD for in vivo hemodynamic performance and biocompatibility. The device is composed of an actuator, blood pump housing, diaphragm, pusher plate, and bioprosthetic valves. Its protein-coated ("biolized") blood-contacting surface inhibits clot formation. Forces between moving parts of the actuator are transmitted magnetically, eliminating a primary source of friction and wear. The pump fills passively and is highly preload sensitive. The device was implanted into three calves for 90, 10, and 57 days, respectively. No anticoagulants were given postoperatively. The device functioned without technical problems during the entire course of each experiment, with mean device flow ranging between 5.4 and 9.0 L/min. Autopsy of the first two calves revealed no sign of embolization and clean blood-contacting surfaces of the devices. The third experiment was complicated by a prosthetic valve endocarditis with infectious embolization, and a few small depositions were found in the pump. In conclusion, the MagScrew VAD has demonstrated a high level of performance and biocompatibility in three calves studied for 10-90 days. Vigorous development is in progress to bring this device to preclinical readiness and thus provide surgeons with the VAD of choice for permanent implantation.

Animals↗
PubMedDate not supplied

Reading and writing in the field of mechanical circulatory support.

Today there is a multiplicity of options for publishing scientific research work. In a specialized field like blood pump studies it is readily established that a very small number of journals publish the vast majority of work. Reading and publishing in those journals will provide the quickest exposure of the work to the most specifically interested and relevant people, even if the "impact factors" of those journals do not have stratospheric values.

Heart, Artificial↗
PubMedDate not supplied

Evaluation of computational models for hemolysis estimation.

The potential for mechanical erythrocyte damage, or hemolysis, in heart valves and blood pumps has been estimated using computational fluid dynamics (CFD) analysis, combined with mathematical models of red cell damage mechanisms. To date, these prediction approaches have not been compared with each other in common benchmark cases, nor have they been evaluated in radically different flow geometries. In this study, four test devices, including a hemoresistometer, a spinning disk, a capillary tube, and a concentric cylinder viscometer were hemolysis tested and computationally simulated. A number of existing models were used to predict blood damage and these models were compared with each other and with actual measurement of hemolysis. The study indicates that the effectiveness of blood damage prediction from the existing models is similar and can potentially be improved with the consideration of a proposed repeated flow passage effect. It also indicates that the improved models can be used to more effectively predict blood damage in widely different situations.

Animals↗
PubMedDate not supplied

Mechanical fragility calibration of red blood cells.

Mechanical fragility of red blood cells (RBCs) is a critical variable for the hemolysis testing of many important clinical devices, such as pumps, valves, and cannulae, and gas exchange devices. Unfortunately, no standardized test for RBC mechanical fragility is currently well accepted. Although many test devices have been proposed for the study of mechanical fragility of RBCs, no one has ever shown that their results have any relevance to a blood pump. Therefore, the fundamental objective of this study was to determine if one or more test devices could be validated as calibrators to document the fragility of the test blood used for any particular test blood. We compared five mechanical fragility test systems to each other and to a Biopump, with respect to hemolysis. All five devices seem to measure the same parameter; the hemoresistometer most closely matched the pump test results, but the stainless steel bead test may be the most practical for routine calibration purposes.

Animals↗
PubMedDate not supplied

The pedipump: development status of a new pediatric ventricular assist device.

The PediPump is a new rotary dynamic ventricular assist device designed specifically for pediatric applications. Although it is capable of providing support for adults, the small size of the PediPump makes it suitable for newborn circulatory support while retaining excellent hemodynamics. Current and future development plans include: (1) determination of the basic engineering requirements for hardware and control logic, including design analysis for system sizing, evaluation of control concepts and bench testing of prototypes; (2) performance of preclinical anatomical fitting studies using computed tomography-based three-dimensional modeling; and, (3) evaluation with animal studies to provide characterization and reliability testing of the device.

Child↗
PubMedDate not supplied

Performance and reliability of the CPB/ECMO Initiative Forward Lines Casualty Management System.

The Cleveland Clinic Foundation CPB/ECMO Initiative Forward Casualty Management System is an economical, compact, transportable, disposable system designed to permit a rapid expansion of trauma management services requiring cardiopulmonary bypass (CPB) or extracorporeal membrane oxygenation (ECMO) pulmonary support. The system, composed of a rotary blood pump, a pump motor driver, and an electronic control console as the blood pumping subsystem, also includes commonly used compatible commercial oxygenators, venous reservoirs, and cannulae. In vitro durability testing accumulated over 100 hours without failure. In vivo reliability was tested in 10 calves under general anesthesia during 6 hours of CPB and ECMO under full heparinization at nominal operating conditions of 4-5 l/min and 2-4 l/min blood flow respectively, and mean arterial pressures between 65 and 100 mm Hg. A mean time to failure of 57 hours was reached during the animal series. Results of these test series demonstrated that this system has the capability to reliably operate during a 6-hour conventional CPB or ECMO procedure, while providing flexibility and ease of use for the operator.

Animals↗