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The Venous System
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Artin A. Shoukas and Carl F. Rothe
Because the blood vessels are elastic and have smooth muscle in their walls, contraction or relaxation of the smooth muscle can quickly redistribute blood between the periphery and the heart to inuence cardiac lling and thus cardiac output. Even though the right ventricle is not essential for life, its functioning acts to reduce the central venous pressure to facilitate venous return [1]. It largely determines the magnitude of the cardiac output by inuencing the degree of lling of the le heart. Dynamic changes in venous tone, by redistributing blood volume, can thus, at rest, change cardiac output over a range of more than ±20%. e dimensions of the vasculature inuence both blood ow-by way of their resistive properties-and contained blood volume-by way of their capacitive properties. e arteries have about 10 times the resistance of the veins, and the veins are more than 10 times as compliant as the arteries.
Lessons Learned from the Porcine CARPA Model: Constant and Variable Responses to Different Nanomedicines and Administration Protocols
Published in Raj Bawa, János Szebeni, Thomas J. Webster, Gerald F. Audette, Immune Aspects of Biopharmaceuticals and Nanomedicines, 2019
Rudolf Urbanics, Péter Bedőcs, János Szebeni
Figure 11.1 illustrates the setup and instruments used in the model. In brief, domestic pigs (usually 2–3 months old) or miniature pigs are initially sedated (with Calypsol/Xilazine) and, after tracheal intubation, anesthetized with isoflurane while breathing spontaneously. The animals thereafter undergo surgery to place multiple catheters into their circulation for the measurement of different hemodynamic parameters, administration of test drugs and blood sampling. Namely, a Swan-Ganz catheter is placed to the pulmonary artery wedge, for the measurement of pulmonary arterial pressure (PAP), and (optionally) central venous pressure (CVP) and cardiac output (CO). Additional catheters are placed into the femoral artery to record the systemic arterial pressure (SAP) and, (optionally), left ventricular end-diastolic pressure (LVEDP). The left femoral vein is canulated for blood sampling, and the external jugular vein for the administration of test articles and to maintain a slow drop infusion of saline (~3 mL/kg/h). For more sophisticated hemodynamic analysis to measure systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR), additional catheters are placed and measurements and calculations are carried out. The hemodynamic, EKG and respiratory parameters are measured continuously, while blood cell counts, O2 saturation, blood analytes (inflammatory and vasoactive mediators) and temperature are measured at predetermined times, usually in 10–20 min intervals. EKG leads I-III are placed at the standard Einthoven positions.
Medical cognition and computer support in the intensive care unit: A cognitive engineering approach
Published in Don Harris, Engineering Psychology and Cognitive Ergonomics, 2017
Robert Logie, Jim Hunter, Neil McIntosh, Ken Gilhooly, Eugenio Alberdi, Jan Reiss
The clinical monitoring of patients in the ICU has three objectives: one is to allow confirmation that the patient is stable or is responding appropriately to treatment. A second objective is the early detection of physiological events which occur spontaneously, with a view to rectifying problems before they become too established. The third is to detect situations in which the patient fails to respond to a particular therapeutic intervention, thereby requiring alternative action. Information technology is intended to assist in the achievement of these objectives, and intensive care wards for both adults and infants have seen a rapid increase in the data available to the clinical staff. Cardio-vascular data (e.g. heart rate, systemic arterial pressures, central venous pressure, and temperatures) have been available for monitoring on a continuous basis for some time. In addition, sensors are now capable of providing measures of cardiac output and the extent of oxygen saturation in the blood. However, physiological conditions can be indicated by changes in several of these parameters. Each may be displayed on a separate monitor in a different format, resulting in complications for the physician or nurse scanning and assimilating the data.
Optimizing sprint interval exercise for post-exercise hypotension: A randomized crossover trial
Published in European Journal of Sport Science, 2023
Sascha Ketelhut, Martin Möhle, Tina Gürlich, Laura Hottenrott, Kuno Hottenrott
It is generally agreed that several peripheral hemodynamic changes occur after exercise that result in alterations in regional and total peripheral resistance (release of local vasodilators due to changes in blood flow), cardiac output (stroke volume and/or heart rate), and plasma volume (Chen and Bonham, 2010). The reduction in total peripheral resistance (TPR) has often been discussed as one of the main mechanisms of PEH, which leads to an increase in venous pooling, producing a drop in central venous pressure and left ventricular preload (Halliwill, 2001). This consecutively leads to a reduction in stroke volume. Even though HR is increased, especially after high-intensity exercise (Jones et al., 2020), the resulting increase in cardiac output is not substantial enough to counteract the drop in TPR. Thus BP is reduced, producing PEH (Kenney and Seals, 1993). Based on this assumption, it could be debated that the difference between R3 and R1 could arise either from differences in TPR modulation or from differences in cardiac output after exercise.
Effects of continuous and pulsatile flows generated by ventricular assist devices on renal function and pathology
Published in Expert Review of Medical Devices, 2018
Takuma Miyamoto, Jamshid H. Karimov, Kiyotaka Fukamachi
What are the risk factors for renal dysfunction? Palomba et al. [40] developed a specific prognostic score for acute kidney injury (AKI) following cardiac surgery. Variables selected for their logistic regression model and inclusion in the final prognostic score were the following: age, combined surgery, cardiopulmonary bypass (CPB) time >120 min, central venous pressure (CVP) >14 cm H2O, low cardiac output, congestive HF (New York Heart Association functional classification >2), preoperative capillary glucose >140 mg/dl, and Cre >1.2 mg/dl. Gambardella et al. [41] showed the incidence of postoperative AKI is 18.2% in the whole cardiac surgery realm, requiring RRT in 2.1% of cases. Of all hemodynamic variables, only low cardiac output and CVP were independent risk factors for postoperative AKI. Specifically, using univariate regression, when the CVP value reached the threshold of 14 mm Hg in the immediate postoperative period, the risk of AKI increased twofold.