A classic learning opportunity from Arthur Guyton and colleagues (1955): circuit analysis of venous return

2007 ◽  
Vol 31 (2) ◽  
pp. 129-135 ◽  
Author(s):  
Douglas Curran-Everett
Keyword(s):  
Cardiovascular System ◽  
Venous Return ◽  
Opportunity To Learn ◽  
Systemic Circulation ◽  
Circuit Analysis ◽  
Learning Opportunity ◽  
Data Graphics ◽  
Electric Analog ◽  
Classic Paper ◽  
Physiological Systems

The circuit analysis of an electric analog of the systemic circulation, the focus of a classic paper by Guyton, Lindsey, and Kaufmann, provides a framework for understanding the factors that impact venous return and for appreciating the value of modeling physiological systems. The classic 1955 paper by Guyton, Lindsey, and Kaufmann gives your students an opportunity to learn about modeling from the physiologist who pioneered it (Guyton) and demonstrates that mathematics and data graphics are fundamental tools with which to learn about the regulation of the cardiovascular system. In this essay, I outline avenues of discovery by which your students can explore the factors that impact venous return.

A classic learning opportunity from Fenn, Rahn, and Otis (1946): the alveolar gas equation

2006 ◽  
Vol 30 (2) ◽  
pp. 58-62 ◽  
Author(s):  
Douglas Curran-Everett
Keyword(s):  
Gas Exchange ◽  
Human Performance ◽  
Meaningful Learning ◽  
Opportunity To Learn ◽  
Pulmonary Gas Exchange ◽  
Respiratory Physiology ◽  
Learning Opportunity ◽  
Data Graphics ◽  
Classic Paper

The alveolar gas equation, the focus of a classic paper by Fenn, Rahn, and Otis, provides a framework for understanding the mechanisms involved in pulmonary gas exchange as well as the limits of human performance. The classic 1946 paper by Fehn, Rahn, and Otis gives your students an opportunity to learn about the alveolar gas equation from the physiologists who pioneered it and demonstrates that mathematics and data graphics are fundamental tools with which to learn respiratory physiology. In this essay, I outline avenues of discovery by which your students can explore the alveolar gas equation. Meaningful learning stems from inspiration: to learn, you must be inspired to learn. If anyone can inspire learning in respiratory physiology, it is Wallace Fenn, Hermann Rahn, and Arthur Otis.

Identification of Compensatory Arterial Dynamics in Swine Using a Non-Invasive Sensor for Local Vascular Resistance

2018 ◽  
Author(s):  
Lu Wang ◽  
Sardar Ansari ◽  
Kevin R. Ward ◽  
Kayvan Najarian ◽  
Kenn R. Oldham
Keyword(s):  
Cardiovascular System ◽  
Vascular Resistance ◽  
Systemic Circulation ◽  
Test Subject ◽  
Loop Model ◽  
Peripheral Vascular ◽  
Dynamics Model ◽  
Non Invasive ◽  
Peripheral Arterial ◽  
Pressure Changes

Autoregulatory dynamics of the cardiovascular system play an important role in maintaining oxygenated blood transportation throughout the human body. In this work, a feedback dynamics model of the cardiovascular system with respect to heartrate and peripheral vascular resistance effects on longer-term blood pressure changes in the systemic circulation is presented. The model is identified from data taken from a swine test subject, instrumented in part with a wearable, non-invasive sensor for estimating peripheral arterial radius. Comparative simulations for the open and close loop model highlight significantly changed hemodynamics after hemorrhage.

ASSESSMENT OF THE MATERNAL VENOUS CIRCULATION: WHY IS IT RELEVANT?

2013 ◽  
Vol 24 (3) ◽  
pp. 194-199
Author(s):  
KATHLEEN TOMSIN ◽  
WILFRIED GYSELAERS
Keyword(s):  
Cardiac Output ◽  
Organ Dysfunction ◽  
Venous Return ◽  
Cardiovascular Disorder ◽  
Systemic Circulation ◽  
Renal Vein Thrombosis ◽  
Venous System ◽  
Total Blood ◽  
Venous Circulation ◽  
Cardiovascular Assessment

The venous system is considered the main capacitor of the human body. Approximately 70% of the total blood volume resides in the venous bed, half of which circulates as venous return whereas the other half functions as reserve volume in the splanchnic veins. These veins are richly innervated and highly compliant, and communicate with the systemic circulation via capillaries (entrance) and portal vein and liver (exit). This constitution allows the venous compartment to balance circulating and stored blood volumes, and thus control cardiac output. Clinical conditions with reduced cardiac output are often associated with hampered venous return, resulting in visceral oedema, ascites or organ dysfunction. Organ dysfunction or failure may also result from (sub)obstructed venous outflow, as is illustrated in renal vein thrombosis or in the Nutcracker syndrome. Recently, the application of Doppler ultrasonography in the study of the maternal venous system illustrated that preeclampsia is another cardiovascular disorder with dysfunctional venous haemodynamics. In this opinion paper, we summarise results from Doppler studies of the maternal venous compartment, illustrating that performing venous haemodynamics function tests is to become a fundamental part of an integrated cardiovascular assessment of women with hypertension in pregnancy, facilitating an individualised diagnostic and therapeutic approach for every woman at risk for gestational hypertensive disease.

scholarly journals In search of “hepatic factor:” Lack of evidence for ALK1 ligands BMP9 and BMP10

2020 ◽  
Author(s):  
Teresa L. Capasso ◽  
Sara M. Trucco ◽  
Morgan Hindes ◽  
Tristin Schwartze ◽  
Jamie L. Bloch ◽  
...  
Keyword(s):  
Single Ventricle ◽  
Venous Return ◽  
Superior Vena ◽  
Plasma Concentrations ◽  
Pulmonary Arteries ◽  
Vena Cava ◽  
Systemic Circulation ◽  
Pulmonary Vasculature ◽  
Morphogenetic Protein ◽  
Bone Morphogenetic Protein 9

AbstractIn children with single ventricle physiology, the Glenn procedure is performed to redirect venous return from the superior vena cava directly to the pulmonary arteries and route venous return from the inferior vena cava exclusively to the systemic circulation. Although this surgery successfully palliates the hemodynamic stress experienced by the single ventricle, patients frequently develop pulmonary arteriovenous malformations (PAVMs). Interestingly, PAVMs may regress upon rerouting of hepatic venous effluent to the pulmonary vasculature, suggesting the presence of a circulating “hepatic factor” that is required to prevent PAVMs. Here, we test the hypothesis that hepatic factor is bone morphogenetic protein 9 (BMP9) and/or BMP10. These circulating ligands are produced by the liver and activate endothelial endoglin (ENG)/ALK1 signaling, and mutations in ENG and ALK1 cause hereditary hemorrhagic telangiectasia, a genetic disease associated with AVM development. However, we found no within-subject variation in BMP9, BMP10, or BMP9/10 plasma concentrations when sampled from five cardiovascular sites, failing to support the idea that the Glenn would limit access of these ligands to the lung vasculature. Unexpectedly, however, we found a significant decrease in all three ligand concentrations in Glenn cases versus controls. Our findings suggest that BMP9/BMP10/ENG/ALK1 signaling may be decreased in the Glenn vasculature but fail to implicate these ligands as hepatic factor.

Simulation Study of the Interaction between Respiration and the Cardiovascular System

1997 ◽  
Vol 36 (04/05) ◽  
pp. 261-263 ◽  
Author(s):  
Jing Bai ◽  
Hongli Lu ◽  
Jupeng Zhang ◽  
Xiaoqiang Zhou
Keyword(s):  
Mathematical Model ◽  
Computer Simulation ◽  
Cardiovascular System ◽  
Simulation Study ◽  
External Pressure ◽  
Respiratory Pattern ◽  
Simulation Studies ◽  
Simulation Results ◽  
Thoracic And Abdominal ◽  
Physiological Systems

Abstract.Many studies have been done on the respiratory and the cardiovascular system. Among them, only a few are on the interaction of these two physiologic systems. To explore the mechanism of the integration of these two physiological systems, computer simulation has been done; we report the preliminary results obtained in our laboratory. In this study, a mathematical model of the cardiovascular system integrated with the respiratory mechanical system has been established. The model is based on our previous work on cardiovascular modeling. The previous lumped lungi model has been replaced by a multielement model with more detail. Inter- thoracic and abdominal pressures are modeled as external pressure sources on the related cardiovascular elements. Using this model, a sequence of simulation studies have been carried out. Different respiratory modes have been simulated and the different effects are observed in the simulation results. The results indicate that by following a certain respiratory pattern, the circulation status can be improved. These results agree with clinical observations.Keywords: Mathematical Model, Respiration Mode, Cardiovascular System, Computer Simulation, Interaction

scholarly journals Towards enabling a cardiovascular digital twin for human systemic circulation using inverse analysis

2020 ◽  
Author(s):  
Neeraj Kavan Chakshu ◽  
Igor Sazonov ◽  
Perumal Nithiarasu
Keyword(s):  
Cardiovascular System ◽  
Inverse Analysis ◽  
Short Term Memory ◽  
Systemic Circulation ◽  
The Body ◽  
Digital Twin ◽  
Patient Database ◽  
Health Care Infrastructure ◽  
Analysis System ◽  
High Degree

Abstract An exponential rise in patient data provides an excellent opportunity to improve the existing health care infrastructure. In the present work, a method to enable cardiovascular digital twin is proposed using inverse analysis. Conventionally, accurate analytical solutions for inverse analysis in linear problems have been proposed and used. However, these methods fail or are not efficient for nonlinear systems, such as blood flow in the cardiovascular system (systemic circulation) that involves high degree of nonlinearity. To address this, a methodology for inverse analysis using recurrent neural network for the cardiovascular system is proposed in this work, using a virtual patient database. Blood pressure waveforms in various vessels of the body are inversely calculated with the help of long short-term memory (LSTM) cells by inputting pressure waveforms from three non-invasively accessible blood vessels (carotid, femoral and brachial arteries). The inverse analysis system built this way is applied to the detection of abdominal aortic aneurysm (AAA) and its severity using neural networks.

Glucose Degradation Products Result in Cardiovascular Toxicity in a Rat Model of Renal Failure

2010 ◽  
Vol 30 (1) ◽  
pp. 35-40 ◽  
Author(s):  
Sandra Müller–Krebs ◽  
Lars P. Kihm ◽  
Benjamin Zeier ◽  
Marie-Luise Gross ◽  
Anders Wieslander ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cardiovascular System ◽  
Degradation Products ◽  
Systemic Circulation ◽  
Sprague Dawley ◽  
Glucose Degradation Products ◽  
Cardiovascular Damage ◽  
Sprague Dawley Rats ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

BackgroundIt has been shown that glucose degradation products (GDP) generated during heat sterilization of peritoneal dialysis (PD) fluids impair the peritoneal membrane locally, then enter the systemic circulation and cause damage to the remnant kidney. Here we examined in subtotally nephrectomized (SNX) rats whether GDP also affect the cardiovascular system.Materials and MethodsStandard 5/6 nephrectomy was carried out in Sprague–Dawley rats; other rats were sham operated and left untreated for 3 weeks. Through an osmotic mini-pump, SNX+GDP group received GDP intravenously for 4 weeks; the SNX and the sham-operated groups remained without GDP. The experiment was terminated for all groups 7 weeks postoperatively. We analyzed cardiovascular damage by serum analyses and immunohistochemical investigation.ResultsIn SNX+GDP animals, expression of the advanced glycation end product (AGE) marker carboxymethyllysine and receptor of AGE (RAGE) were significantly higher in the myocardium and the aorta compared to the SNX rats. We also found significantly higher levels of apoptosis measured by caspase 3 staining in the cardiovascular system in the SNX+GDP group. Moreover, we observed a more pronounced expression of oxidative stress in the SNX+GDP rats compared to the SNX rats. In serum analyses, advanced oxidation protein products and reactive oxygen species were increased, as was immunohistochemical endothelial nitric oxide synthase.ConclusionsIn addition to local toxic effects, GDP cause systemic toxicity. Here we showed that, in SNX rats, administration of GDP increased cardiovascular damage. In particular, we found increased levels of AGE, RAGE, oxidative stress, and apoptosis. Whether these findings are of clinical relevance has to be further investigated.

What Goes Around Comes Around—Venous Return

2011 ◽  
pp. 48-54
Author(s):  
James R. Munis
Keyword(s):  
Cardiac Output ◽  
Steady State ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Cardiovascular System ◽  
Venous Return ◽  
Atrial Pressure ◽  
Right Atrial ◽  
Interconnected System ◽  
The Mean

By its nature, circulatory physiology is also susceptible to circular reasoning because every part of an interconnected system is affected by, and affects, every other part. If we're not careful, we end up saying things like ‘venous return equals cardiac output’ when, in the steady state, that is true by definition and nothing new is gained. If we grant that right atrial pressure (PRA) is the ‘downstream’ pressure for venous return, then it follows that PRA should be inversely related to venous return (and therefore, to cardiac output). If we simply apply Ohm's law to the cardiovascular system, we forget that the mean arterial pressure not only contributes to venous return but also is sustained by venous return. If venous return fails for any other reason (unrelated to arterial pressure), so too will mean arterial pressure eventually fail.

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