Biomedical Engineering and Bioengineering Commons^™

Influence Of Isoflurane On Left Atrial Function In Dogs With Pacing-Induced Cardiomyopathy: Evaluation With Pressure-Volume Relationships, Franz Kehl, John F. Ladisa, Douglas Anthony Hettrick, Judy R. Kersten, David C. Warltier, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

Objective

The actions of volatile anesthetics on left ventricular (LV) function in normal and failing hearts have been previously evaluated, but the effects of these agents on left atrial (LA) function in the presence of LV dysfunction are unknown. The hypothesis was tested that isoflurane alters LA mechanics evaluated with pressure-volume relations.

Design

Prospective.

Setting

Laboratory.

Participants

Barbiturate-anesthetized dogs (n = 8) were instrumented for measurement of aortic, LA, and LV pressures (micromanometers), and LA volume (epicardial orthogonal sonomicrometers) after 3 weeks of rapid ventricular pacing (220 beats/min).

Interventions

LA myocardial contractility (E_es) was assessed with end-systolic pressure-volume …

Reactive Oxygen Species Modulate Coronary Wall Shear Stress And Endothelial Function During Hyperglycemia, Eric R. Gross, John F. Ladisa, Dorothee Weihrauch, Lars E. Olson, Tobias T. Kress, Douglas Anthony Hettrick, Paul S. Pagel, David C. Warltier, Judy R. Kersten

Biomedical Engineering Faculty Research and Publications

Hyperglycemia is associated with generation of reactive oxygen species (ROS), and this action may contribute to accelerated atherogenesis. We tested the hypothesis that hyperglycemia produces alterations in left anterior descending coronary artery (LAD) wall shear stress concomitant with endothelial dysfunction and ROS production in dogs (n = 12) instrumented for measurement of LAD blood flow, velocity, and diameter. Dogs were randomly assigned to receive vehicle (0.9% saline) or the superoxide dismutase mimetic 4- hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (tempol) and were administered intravenous infusions of d-glucose to achieve target blood glucose concentrations of 350 and 600 mg/dl (moderate and severe hyperglycemia, respectively). Endothelial …

Adenosine Type 1 (A ) Receptors Mediate Protection Against Myocardial 1 Infarction Produced By Chronic, Intermittent Ingestion Of Ethanol In Dogs, Franz Kehl, John G. Krolikowski, John F. Ladisa, Judy R. Kersten, David C. Warltier, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

Background: Chronic consumption of small amounts of ethanol protects myocardium from ischemic injury. We tested the hypothesis that adenosine type 1 (A₁) receptors mediate these beneficial effects.

Methods: Dogs (n=37) were fed with ethanol (1.5 g/kg) or water mixed with dry food twice per day for 12 weeks, fasted overnight before experimentation, and instrumented for measurement of hemodynamics. Dogs received intravenous drug vehicle (50% polyethylene glycol in 0.1 N sodium hydroxide and 0.9% saline over 15 min) or the selective A₁ receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 0.8 mg/kg over 15 min) and were subjected …

Nonlinear Elastic Material Property Estimation Of Lower Extremity Residual Limb Tissues, Ergin TöNüK, M. Barbara Silver-Thorn

Biomedical Engineering Faculty Research and Publications

The interface stresses between the residual limb and prosthetic socket have been studied to investigate prosthetic fit. Finite-element models of the residual limb-prosthetic socket interface facilitate investigation of the mechanical interface and may serve as a potential tool for future prosthetic socket design. However, the success of such residual limb models to date has been limited, in large part due to inadequate material formulations used to approximate the mechanical behavior of residual limb soft tissues. Nonlinear finite-element analysis was used to simulate force-displacement data obtained during in vivo rate-controlled (1, 5, and 10 mm/s) cyclic indentation of the residual limb …

Measuring The Effect Of Airway Pressure On Pulmonary Arterial Diameter In The Intact Rat Lung, Robert C. Molthen, Steven Thomas Haworth, Amy Heinrich, Christopher A. Dawson

Biomedical Engineering Faculty Research and Publications

To study the relationship between transpulomnary [sic] pressure (Ptp), intravascular pressure (Pv), and the pulmonary arterial tree structure, morphometric measurements of pulmonary arterial trees were made in intact lungs from Sprague-Dawley rats. Using cone beam micro-CT and techniques we developed for imaging small animal lungs, volumetric CT data were acquired for Ptp from 0 - 12 mmHg and Pv from 5 - 30 mmHg. The diameter, D (measured range approximately 0.08-2.0 mm), vs. pressure, P, relation can be described by D(P) = D(0)(1+ α P), where α is a distensibility coefficient. Unlike studies performed in larger animals, where changes in …

Spect Imaging Of Pulmonary Blood Flow In A Rat, Christian Wieholt, Robert C. Molthen, Roger H. Johnson, Christopher A. Dawson, Anne V. Clough

Biomedical Engineering Faculty Research and Publications

Small animal imaging is experiencing rapid development due to its importance in providing high-throughput phenotypic data for functional genomics studies. We have developed a single photon emission computed tomography (SPECT) system to image the pulmonary perfusion distribution in the rat. A standard gamma camera, equipped with a pinhole collimator, was used to acquire SPECT projection images at 40 sec/view of the rat thorax following injection of Tc99m labeled albumin that accumulated in the rat's lungs. A voxel-driven, ordered-subset expectation maximization reconstruction was implemented. Following SPECT imaging, the rat was imaged using micro-CT with Feldkamp conebeam reconstruction. The two reconstructed image …

Sensitivity To Hand Path Curvature During Reaching, Kyle P. Lillis, Robert A. Scheidt

Biomedical Engineering Faculty Research and Publications

People optimize reaching to make straight and smooth movements. We performed experiments characterizing human sensitivity to hand path deviations from a straight reach. Vision of the arm was blocked. Subjects either moved the hand along paths of constrained curvature, or a robot moved the relaxed limb along similar trajectories (active and passive conditions, respectively). Subjects responded after each trial whether or not they thought the movement curved convex right. In a series of three experiments, we tested the effects of modifying visual feedback of hand position to suppress curvature, isotonic muscle activation, and a distracter task on subjects ability to …

Mechanisms Of Volatile Anesthetic-Induced Myocardial Protection, Lynda M. Ludwig, Judy R. Kersten, Katsuya Tanaka, Weidong Gu, John F. Ladisa, David C. Warltier, Paul S. Pagel

Biomedical Engineering Faculty Research and Publications

Volatile anesthetics protect myocardium against reversible and irreversible ischemic injury. Experimental evidence from several in vitro and in vivo animal models demonstrates that volatile agents enhance the recovery of stunned myocardium and reduce the size of myocardial infarction after brief or prolonged coronary artery occlusion and reperfusion, respectively. This protective effect persists after the anesthetic has been discontinued, a phenomenon known as anesthetic-induced preconditioning (APC). Recent clinical data also demonstrates evidence of APC in patients during cardiac surgery. Thus, administration of volatile anesthetics may represent a novel therapeutic approach that reduces morbidity and mortality associated with perioperative myocardial ischemia and …

Three-Dimensional Reconstruction Algorithm For A Reverse-Geometry Volumetric Ct System With A Large-Array Scanned Source, Taly Gilat Schmidt, Rebecca Fahrig, Norbert J. Pelc

Biomedical Engineering Faculty Research and Publications

We have proposed a CT system design to rapidly produce volumetric images with negligible cone beam artifacts. The investigated system uses a large array scanned source with a smaller array of fast detectors. The x-ray source is electronically steered across a 2D target every few milliseconds as the system rotates. The proposed reconstruction algorithm for this system is a modified 3D filtered backprojection method. The data are rebinned into 2D parallel ray projections, most of which are tilted with respect to the axis of rotation. Each projection is filtered with a 2D kernel and backprojected onto the desired image matrix. …