Technology and Health Care - Volume 9, issue 5

Authors: Donovan Jr., Francis M. | Taylor, Bruce C.

Article Type: Research Article

Abstract: Cardiac output is measured by the thermal dilution method which uses a quadruple lumen catheter, with a thermistor on the tip, through the right atrium, right ventricle and into the pulmonary artery. Cold saline is injected into the right atrium and the resulting pulmonary artery temperature profile is integrated. The same procedure performed with three thermistors and three pressure sensors located on the catheter to measure temperature and pressure in the atrium, ventricle and artery respectively will produce a set of temperature and pressure curves with shapes determined by injectate temperature, injectate volume, heart rate, systolic time interval, body temperature, …cardiac output, volumes, flow rates and valve openings. A digital computer program has been developed to optimize the fit of a lumped parameter model to the thermodilution curves in order to determine heart rate, systolic time as a fraction of cardiac cycle, right atrial systolic and diastolic volumes, ventricular systolic and diastolic volumes, cardiac output, inflow valve forward and reverse flow rates and effective diameters, outflow valve forward and reverse flow rates and effective diameters, ventricular power and efficiency. The program has been tested over a range of operating conditions including noise in the temperature and pressure signals, randomly varying heart rate and cardiac cycle. All of the data for the tests were produced by a digital computer simulation of a pulsatile artificial heart. The results of these tests indicate that the enhanced thermal dilution analysis method is feasible. Show more

DOI: 10.3233/THC-2001-9501

Citation: Technology and Health Care, vol. 9, no. 5, pp. 377-386, 2001

Authors: Schalin, L. | Liepsch, D.

Article Type: Research Article

Abstract: Flow behavior and velocity were studied in six varicose vein models with simulated arteriovenous anastomoses (AVAs). Experiments were performed to determine whether incoming flow entering from AV-anastomoses or small feeder veins could create either small jet streams or velocity fluctuation, which might then cause veins to bulge and get tortuous. Flow was analyzed in areas of flow change. Studies were performed in rigid Plexiglas and elastic, silicon rubber models that exactly replicated the geometry and compliance of varicose veins. Flow was visualized with dyes for steady flow and with a birefringent solution for pulsatile flow studies. Local velocity was measured …with a laser-Doppler-anemometer (LDA). Very low forces and shear stresses were found on the interior wall opposite the entrance of the simulated AV anastomoses. However, these values were ten times that of an idealized flow in a straight tube without added flow from simulated AV anastomoses. Show more

DOI: 10.3233/THC-2001-9502

Citation: Technology and Health Care, vol. 9, no. 5, pp. 387-402, 2001

Authors: Lombardi, R. | Buizza, A. | Gandolfi, R. | Vignarelli, C. | Guaita, A. | Panella, L.

Article Type: Research Article

Abstract: A measurement system and associate signal processing procedures for quantifying subject's performance during the performance-oriented assessment of balance as defined in Tinetti test (TT) is described. It is based on two inclinometers measuring trunk inclination in two orthogonal planes. Signals from the transducers are acquired by a PC through A/DC board. Signal processing consists in computing morphological parameters describing the main features of subject movement during the different TT maneuvers. The system is simple, cheap, user friendly, causes no discomfort to the patient and can easily be modified to comply with either new requirements or the needs of other performance …tests dealing with trunk movement. Preliminary results of measurements on both normals and patients suggest the viability of this approach and the possibility of discriminating normal from abnormal performance, based on the values of the morphological parameters. Show more

DOI: 10.3233/THC-2001-9503

Citation: Technology and Health Care, vol. 9, no. 5, pp. 403-415, 2001

Authors: Andersson, Roger | Ask, Per

Article Type: Research Article

Abstract: A sensor has been designed consisting of a tube holder with a force transducer and a tube with a modified cross-section. The holder has a lid that encloses the tube. By having a stiff holder and a compliant tube, the idea is that the intraluminal pressure in the tube can be obtained from the measured force. The method is intended for non-invasive pressure measurements in blood or dialysate tubes. We have used a tube cross-sectional geometry where the outer surface is elliptic and the inner surface is circular with a relation of 2:1 between the thinnest and thickest tube …sides. The pressure transducer system shows a linear relationship between the applied pressure and the sensor output (r=0.999). Within the temperature range, 32°–36°C, which corresponds to the blood and dialysate temperatures, the sensor accuracy is within ± 0.8 kPa (± 6 mm Hg). This indicates that the sensor should be clinically useful during dialysis and similar applications. Show more

Keywords: non-invasive pressure sensor, asymmetric tube, dialysis, extracorporeal tube, profile analysis

DOI: 10.3233/THC-2001-9504

Citation: Technology and Health Care, vol. 9, no. 5, pp. 417-425, 2001

Authors: Chang, Xiaofei | Zeng, Yanjun | Yu, Hongmei | Hu, Jinlin

Article Type: Research Article

Abstract: Using the whole-cell patch-clamp technique, we recorded delayed outward currents in rat brain microvascular endothelial cells (BRMECs), which were nearly completely inhibited by 20 mmol/L extracellular TEA-Cl and 5 mM extracellular CsCl. Whole-cell currents were elicited under voltage clamp condition by 2100 ms depolarizing voltage pulses applied every 7 s between -100 to 90 mV in 10 mV increment from a holding potential of -100 mV. The currents were defined as delayed rectified K+ currents (IKv), which were inhibited in a concentration-dependent manner by bath application of TEA-Cl, with an IC50 approximately 2.0 mM, similar to that reported on …IKv in other preparations. In the present of mechanical force, outward currents were increased in amplitude as compared with controls. These mechanical force induced currents were also defined as IKv, which are different from previous described mechanosensitive currents with characteristic of inward rectifier. Show more

Keywords: mechanosensitive ion channels, mechanical force, whole-cell patch-clamp technique, rat brain microvascular endothelial cells (RBMECs), delayed rectified currents (IKv)

DOI: 10.3233/THC-2001-9505

Citation: Technology and Health Care, vol. 9, no. 5, pp. 427-432, 2001