Technology and Health Care - Volume 9, issue 3

Authors: Zheng, Z.C.

Article Type: Research Article

Abstract: Because of complicated rheological issues related with sickle cell blood, there exists a practical need to rationally determine critical hematocrit in transfusions for sickle cell patients. In this research, two major effects, i.e. oxygen concentration and hematocrit, are considered in a theoretical hydrodynamic model incorporating oxygen transport and lubrication theory. The pressure drop depends on the compliance of red blood cells, which changes with oxygen concentration in sickle red cells. Under the assumption that after transfusion, the upper limit of the local resistance of a capillary should not surpass that in the same capillary of normal blood flow, critical hematocrit …values with different exchange percentage rates are determined. The current clinical ceiling value of 35 percent for total hematocrit after the transfusion, for the first time, finds its analytical reasoning through mathematical modeling. Plots of critical hematocrit values versus the transfusion exchange percentage are provided in the paper. Show more

Keywords: hemodynamics, sickle cell, transfusion

DOI: 10.3233/THC-2001-9301

Citation: Technology and Health Care, vol. 9, no. 3, pp. 225-236, 2001

Authors: Beer, Nicole A.M. de | Meurs, Willem L. van | Grit, Marco B.M. | Good, Michael L. | Gravenstein, Dietrich

Article Type: Research Article

Abstract: We describe a model for simulating a spontaneous electroencephalogram (EEG) and for simulating the effects of anesthesia on the EEG, to allow anesthesiologists and EEG technicians to learn and practice intraoperative EEG monitoring. For this purpose, we developed a linear model to manipulate the amplitude of the activity in each of the traditional EEG frequency bands. Burst suppression patterns are simulated by manipulating an overall gain. To demonstrate the model feasibility, model parameters for thiopental and isoflurane were estimated guided by published data on the EEG effects of these anesthetic drugs. Using these estimates, EEG time signals were simulated for …isoflurane at various partial pressures, and for bolus intravenous doses of thiopental. Comparison with actual recorded EEG signals showed that the changes produced by isoflurane and thiopental in the simulated signals are very similar to the changes in the actual signals, which was confirmed by two clinicians with experience and routine practice in intraoperative EEG monitoring. Show more

Keywords: electroencephalography, intraoperative monitoring, computer simulation, educational simulation, computer-assisted instruction

DOI: 10.3233/THC-2001-9302

Citation: Technology and Health Care, vol. 9, no. 3, pp. 237-256, 2001

Authors: Gefen, A. | Halpern, P. | Shiner, R.J. | Schroter, R.C. | Elad, D.

Article Type: Research Article

Abstract: Mechanical ventilation has been associated with pulmonary edema in the clinical setting, but the pathophysiological mechanisms of this process have not been clearly defined. Experimental studies have shown that high transpulmonary pressures resulting from ventilation may damage the capillary walls, thereby leading to edema. Knowledge of the stress distribution within the alveolar septa would be an important step in understanding this phenomenon. A newly developed saline-filled alveolar sac model was utilized for analysis of septal stresses in young and aging healthy lungs, in order to examine their vulnerability to pulmonary edema during ventilation. Significant stress concentrations were shown to develop …near highly curved regions (small local radii of less than 4 μm) in a lung inflated to 80% could be as high as 25 times that of average septal stresses. The combination of elevated stress sites that are formed in the stiffer parenchyma of the aging lung, together with the cyclic loading of ventilation, may explain the gaps and breaks previously observed in pulmonary edema. Show more

Keywords: mechanical ventilation, lung parenchyma, alveolar wall, finite element method, high-altitude / exercise-induced edema

DOI: 10.3233/THC-2001-9303

Citation: Technology and Health Care, vol. 9, no. 3, pp. 257-267, 2001

Authors: Elad, D. | Soffer, G. | Zaretsky, U. | Wolf, M. | Shiner, R.J.

Article Type: Research Article

Abstract: Sound signals of respiratory airflow represent summations of acoustic waves of various frequencies, which basically depend on the characteristics of the flow and on those of the surrounding tissue. This study was designed to examine the capability of time-frequency distribution (TFD) of respiratory signals in order to differentiate between unobstructed and obstructed upper airways. In order to investigate the TFD characteristics of defined upper airway geometry we conducted a controlled basic study in a laboratory system with an in vitro isolated airway model, which was either unobstructed or had concentric obstructions of various degrees at different locations along the …tube. Pressure fluctuations were acquired with a microphone proximal to the airway opening. A short-term Fourier transform was used to study the TFDs of these signals. The results of the in vitro study showed that the energy of the higher frequencies increased for relatively small incremental changes in: i) reduction of the lumen cross-section, ii) decrease of distance from measurement site to obstruction, and iii) increase of breathing effort. Further development of this method may lead to noninvasive clinical techniques for early diagnosis of upper airway obstructions. Show more

Keywords: respiratory airflow, sound signals, short-time Fourier transform (STFT), airway obstruction

DOI: 10.3233/THC-2001-9304

Citation: Technology and Health Care, vol. 9, no. 3, pp. 269-280, 2001

Authors: Saxena, A.K. | Topp S, S. | Heinecke, A. | Willital, G.H.

Article Type: Research Article

Abstract: Fever is an important and sensitive indicator of infectious diseases in children. For the past decades, measurement of body temperature in routine medical practice was limited to oral, rectal and axillary sites. In infants and children, however, temperature measurements are further limited to the rectal and axillary sites due to technical and clinical considerations. In the field of pediatric surgery, pathological and surgical conditions of the ano-rectal area often further restrict the application of conventional rectal temperature measurements. The application of tympanic temperature measurements in such pediatric surgical pathologies provides a reliable alternative to conventional rectal temperature measurements. The pediatric …surgical clinico-pathological states where ear temperature measurements are the only mode of accurate temperature determination have been identified. Tympanic thermometry is well tolerated by children and predicts temperature with relative accuracy within a few seconds. Show more

DOI: 10.3233/THC-2001-9305

Citation: Technology and Health Care, vol. 9, no. 3, pp. 281-285, 2001

Authors: Song, Xiaoyan | Zeng, Yanjun | Yu, Hongmei | Hu, Jinlin | Hao, Yanlei

Article Type: Research Article

Abstract: Intercellular adhesion molecule-1 (ICAM-1) is an adherence molecule that is an important factor in many pathophysiological processes such as atherosclerosis, thrombosis and inflammation. It is secretion of endothelial cells by a variety of biochemical stimulations. But hemodynamic forces can also induce various functional changes in vascular endothelium. Some researches have proved that shear stress can modulate the expression of ICAM-1. But most of them examine the regulation of expression of ICAM-1 in human umbilical vein endothelial cells. There is no detail on the effect of shear stress (SS) on ICAM-1 expression of microvascular endothelial cells (RBMECs). In this experiment, we …use cultured rat brain microvascular endothelial cells (RBMECs). By using the parallel plate flow chamber method, we give two magnitudes of lamminar shear stresses (0.2 dyn/cm2 , 0.4 dyn/cm2 ) for different perieods of time on the slides of cells. Immunostaining method and image analysis shows a specific upregulation in ICAM-1 expression on RBMECs, which is different from endothelial cells of other species or vascular beds. Expression of ICAM-1 is increased 0.5h after the onset of SS, and reached its highest level 4h after onset of SS, then declines after that. The effect is time-dependent, not force magnitude-dependent. Endothelial cell surface expression of ICAM-1 in the supernatants of RBMECs exposed to SS was not modified excluding the possibility that RBMECs exposed to SS synthesize factors that upregulate ICAM-1. The experiment data are relevant to the current understanding of basic mechanisms that explain the signal transudation pathway occurring inside the endothelial cells under the effect of SS. Show more

Keywords: shear stress, RBMECs, ICAM-1

DOI: 10.3233/THC-2001-9306

Citation: Technology and Health Care, vol. 9, no. 3, pp. 287-293, 2001