scholarly journals Biophysical Conceptual Doxastic Errors in Arterial Hypertension in Surgical and Medical Management, in the Frame of Navier Stokes Equations

2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Lamothe M ◽  
Lamothe N ◽  
Lamothe D ◽  
Ahumada-Ayala M ◽  
Castillo C ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Energy Density ◽  
Venous Return ◽  
Stokes Equations ◽  
Self Regulation ◽  
Transmural Pressure ◽  
Driving Pressure ◽  
Fourth Power ◽  
Coronary Perfusion ◽  
The Right

Multiple tragic biophysical errors in relation to hypertension in surgery and medicine, constitute conceptual atrocities: 1) Many physicians believe that perfusion decays with the fourth power of the radius, which is the result of a doxastic misunderstanding of the Poiseuille equation. These phenomena are even more transcendent in the case of surgical situations when the homeostatic metastability is more critical and with less margin to be compensated. 2) Furthermore, when seen the occlusion of an artery, frequently, instead of measuring the radius, they measure the apparent cross-sectional area. 3) By reducing the driving pressure with antihypertensive drugs, we are decreasing axial pressure in the flow and consequently the perfusion. 4) The sphygmomanometer measures transmural pressure and not driving pressure which is what produces perfusion. 5) The main hemodynamic cause of damage is not transmural hypertension but Laplacian tension. 6) The damage to the arteries does not depend on transmural pressure but on the energy density per time, in units of Joules per cubic meter per second, or Watts per cubic meter. 7) Hypertension, ceteris parivus, increases perfusion. 8) The baroreceptors do not respond to transmural pressure but to Laplacian arterial tension. 9) The brain and the heart have self-regulation of their perfusion, but vasodilators increase perfusion in other tissues, reducing cerebral and coronary perfusion due to the stolen effect. 10). Strictly, all gradients constitute potential energy, as happens in the instances of the concentration gradients, temperature gradients, pressure gradients, and electrical gradients. 11) The derivative of pressure with respect to time, that is the change in pressure due to change in time, is the derivative of the work per volume per time (change in work density due to time), that is, power density. 12) What determines the perfusion is the axial gradient, not of pressure but energy. 13) Hyperbolically if we consider taking the pressure of a pachyderm, we would obtain readings significantly higher. 14) Pressure is, in reality, energy density, which means, energy per infinitesimal unit of volume. 15) The venous return consists of the blood flow returning to the right heart. Because the input of the right side must equal its output, then in the steady-state situation, the cardiac outputs of the right and left sides are essentially equal. Consequently, the systemic venous return matches the systemic cardiac output. The venous return should be equal to or less than the cardiac output. The heart, as a pump, cannot expel a volume that has not been received; notwithstanding, in the case of valve regurgitation, the heart can expel a fraction of the venous return twice. The clinical physician should ask himself or herself: Is the preload volume in the EDV or the pressure at the time of the EDV which has been diminished before starting the isovolumic contraction?

Mechanism of the Increased Venous Return and Cardiac Output Caused by Epinephrine

1957 ◽  
Vol 192 (1) ◽  
pp. 126-130 ◽  
Author(s):  
Arthur C. Guyton ◽  
Arthur W. Lindsey ◽  
Berry Abernathy ◽  
Jimmy B. Langston
Keyword(s):  
Cardiac Output ◽  
Pressure Gradient ◽  
Spinal Anesthesia ◽  
Right Atrium ◽  
Venous Return ◽  
Operating Conditions ◽  
Total Spinal Anesthesia ◽  
Vascular Walls ◽  
The Mean ◽  
The Right

The effect of epinephrine on venous return has been measured in 11 dogs under total spinal anesthesia. The mechanism by which epinephrine increases venous return seems to be to increase the tone of the vascular walls thereby increasing the mean circulatory pressure. This in turn increases the pressure gradient forcing blood from the systemic vessels toward the right atrium. By equating the recorded venous return curves with curves that depict the effect of epinephrine on the heart's ability to pump blood, it is shown that under normal operating conditions cardiac output is determined far more by the tendency for blood to return to the heart than by the heart's ability to pump blood.

Theoretical analysis of rest and exercise hemodynamics in patients with total cavopulmonary connection

2002 ◽  
Vol 282 (3) ◽  
pp. H1018-H1034 ◽  
Author(s):  
Elisa Magosso ◽  
Silvio Cavalcanti ◽  
Mauro Ursino
Keyword(s):  
Cardiac Output ◽  
Venous Return ◽  
Poor Response ◽  
Intrathoracic Pressure ◽  
Systemic Arterial Pressure ◽  
Regulatory Mechanisms ◽  
Total Cavopulmonary Connection ◽  
The Right ◽  
The Impact ◽  
Cavopulmonary Connection

The objective of this study was to determine the impact of a total cavopulmonary connection on the main hemodynamic quantities, both at rest and during exercise, when compared with normal biventricular circulation. The analysis was performed by means of a mathematical model of the cardiovascular system. The model incorporates the main parameters of systemic and pulmonary circulation, the pulsating heart, and the action of arterial and cardiopulmonary baroreflex mechanisms. Furthermore, the effect of changes in intrathoracic pressure on venous return is also incorporated. Finally, the response to moderate dynamic exercise is simulated, including the effect of a central command, local metabolic vasodilation, and the “muscle pump” mechanism. Simulations of resting conditions indicate that the action of baroreflex regulatory mechanisms alone can only partially compensate for the absence of the right heart. Cardiac output and mean systemic arterial pressure at rest show a large decrease compared with the normal subject. More acceptable hemodynamic quantity values are obtained by combining the action of regulatory mechanisms with a chronic change in parameters affecting mean filling pressure. With such changes assumed, simulations of the response to moderate exercise show that univentricular circulation exhibits a poor capacity to increase cardiac output and to sustain aerobic metabolism, especially when the oxygen consumption rate is increased above 1.2–1.3 l/min. The model ascribes the poor response to exercise in these patients to the incapacity to sustain venous return caused by the high resistance to venous return and/or to exhaustion of volume compensation reserve.

Self-Regulation and Human Progress

2018 ◽  
Author(s):  
Evan Osborne
Keyword(s):  
Scientific Method ◽  
Mutual Influence ◽  
Free Market ◽  
Self Regulation ◽  
Free Expression ◽  
Trial And Error ◽  
Human History ◽  
Economic Context ◽  
The Right ◽  
First Time

Does humanity progress primarily through leaders organizing and directing followers, or through trial and error by individuals free to chart their own path? For most of human history ruling classes had the capacity and the desire to tightly regiment society, to the general detriment of progress. But beginning in the 1500s, Europeans developed a series of arguments for simply leaving well enough alone. First in the form of the scientific method, then in the form of free expression, and finally in the form of the continuously, spontaneously reordered free market, people began to accept that progress is hard, and requires that an immense number of mistakes be tolerated so that we may learn from them. This book tells the story of the development of these three ideas, and for the first time tells of the mutual influence among them. It outlines the rise, and dramatic triumph, of each of these self-regulating systems, followed by a surprising rise in skepticism, especially in the economic context. Such skepticism in the 20th century was frequently costly and sometimes catastrophic. Under the right conditions, which are more frequent than generally believed, self-regulating systems in which participants organize themselves are superior. We should accept their turbulence in exchange for the immense progress they generate.

scholarly journals Performance of a capnodynamic method estimating cardiac output during respiratory failure - before and after lung recruitment

2019 ◽  
Vol 34 (6) ◽  
pp. 1199-1207
Author(s):  
Thorir Svavar Sigmundsson ◽  
Tomas Öhman ◽  
Magnus Hallbäck ◽  
Eider Redondo ◽  
Fernando Suarez Sipmann ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Respiratory Failure ◽  
Reference Method ◽  
Hemodynamic Instability ◽  
Lung Lavage ◽  
Lung Recruitment ◽  
Recruitment Manoeuvre ◽  
Percentage Error ◽  
Before And After ◽  
The Right

AbstractRespiratory failure may cause hemodynamic instability with strain on the right ventricle. The capnodynamic method continuously calculates cardiac output (CO) based on effective pulmonary blood flow (COEPBF) and could provide CO monitoring complementary to mechanical ventilation during surgery and intensive care. The aim of the current study was to evaluate the ability of a revised capnodynamic method, based on short expiratory holds (COEPBFexp), to estimate CO during acute respiratory failure (LI) with high shunt fractions before and after compliance-based lung recruitment. Ten pigs were submitted to lung lavage and subsequent ventilator-induced lung injury. COEPBFexp, without any shunt correction, was compared to a reference method for CO, an ultrasonic flow probe placed around the pulmonary artery trunk (COTS) at (1) baseline in healthy lungs with PEEP 5 cmH2O (HLP5), (2) LI with PEEP 5 cmH2O (LIP5) and (3) LI after lung recruitment and PEEP adjustment (LIPadj). CO changes were enforced during LIP5 and LIPadj to estimate trending. LI resulted in changes in shunt fraction from 0.1 (0.03) to 0.36 (0.1) and restored to 0.09 (0.04) after recruitment manoeuvre. Bias (levels of agreement) and percentage error between COEPBFexp and COTS changed from 0.5 (− 0.5 to 1.5) L/min and 30% at HLP5 to − 0.6 (− 2.3 to 1.1) L/min and 39% during LIP5 and finally 1.1 (− 0.3 to 2.5) L/min and 38% at LIPadj. Concordance during CO changes improved from 87 to 100% after lung recruitment and PEEP adjustment. COEPBFexp could possibly be used for continuous CO monitoring and trending in hemodynamically unstable patients with increased shunt and after recruitment manoeuvre.

Industry-Sponsored Medical Education — In the Quest for Professional Integrity and Legal Certainty

2007 ◽  
Vol 14 (4) ◽  
pp. 313-319
Author(s):  
Benedikt Buchner
Keyword(s):  
Medical Education ◽  
Self Regulation ◽  
State Regulation ◽  
General Question ◽  
Legal Certainty ◽  
European Directive ◽  
Starting Point ◽  
Good Starting Point ◽  
Advertising Law ◽  
The Right

AbstractIndustry-sponsored medical education is a much disputed issue. So far, there has been no regulatory framework which provides clear and definite rules as to whether and under what circumstances the sponsorship of medical education is acceptable. State regulation does not exist, or confines itself to a very general principle. Professional regulation, even though applied frequently, is rather vague and indefinite, raising the general question as to whether self-regulation is the right approach at all. Certainly, self-regulation by industry cannot and should not replace other regulatory approaches. Ultimately, advertising law in general and the European Directive 2001/83/EC specifically, might be a good starting point in providing legal certainty and ensuring the independence of medical education. Swiss advertising law illustrates how the principles of the European Directive could be implemented clearly and unambiguously.

Alterations in Systemic Vascular Volume of the Dog in Response to Hexamethonium and Norepinephrine

1957 ◽  
Vol 191 (2) ◽  
pp. 283-286 ◽  
Author(s):  
John C. Rose ◽  
Edward D. Freis
Keyword(s):  
Cardiac Output ◽  
Venous Return ◽  
Cardiac Activity ◽  
Left Ventricular ◽  
Vascular Volume ◽  
Vasomotor Activity ◽  
Constant Output ◽  
Arteriolar Tone ◽  
Integrated Responses

A diaphragm pump of controlled constant output was substituted for the left ventricle in dogs. Left auricular blood was conducted to a reservoir, from which it was pumped into the thoracic aorta. Left ventricular by-pass was complete. Alterations in total vascular volume were continually monitored by observation of the pump reservoir level. Sympathetic blockade (hexamethonium) increased total vascular volume (mean 15%). This resulted in decreased venous return and decreased right ventricular output. Norepinephrine constricted the total vasculature and decreased vascular volume (mean 12%). This resulted in increased venous return and cardiac output. These experiments demonstrated the complex integrated responses of the total circulation to sympathetic vasomotor activity. The role of the sympathetic nervous system not only in the regulation of arteriolar tone and cardiac activity but also in adjusting total vascular volume and venous return was emphasized. Venous return, and hence cardiac output alterations accompanying systemic vasomotor activity can only be detected by continuous methods of flow measurement.

Governing Fake News: The Regulation of Social Media and the Right to Freedom of Expression in the Era of Emergency

2021 ◽  
pp. 1-41
Author(s):  
Donato VESE
Keyword(s):  
Social Media ◽  
Freedom Of Expression ◽  
Self Regulation ◽  
Public Law ◽  
Fake News ◽  
Human Right ◽  
Social Media Platforms ◽  
Definition Of ◽  
The Right ◽  
Media Censorship

Governments around the world are strictly regulating information on social media in the interests of addressing fake news. There is, however, a risk that the uncontrolled spread of information could increase the adverse effects of the COVID-19 health emergency through the influence of false and misleading news. Yet governments may well use health emergency regulation as a pretext for implementing draconian restrictions on the right to freedom of expression, as well as increasing social media censorship (ie chilling effects). This article seeks to challenge the stringent legislative and administrative measures governments have recently put in place in order to analyse their negative implications for the right to freedom of expression and to suggest different regulatory approaches in the context of public law. These controversial government policies are discussed in order to clarify why freedom of expression cannot be allowed to be jeopardised in the process of trying to manage fake news. Firstly, an analysis of the legal definition of fake news in academia is presented in order to establish the essential characteristics of the phenomenon (Section II). Secondly, the legislative and administrative measures implemented by governments at both international (Section III) and European Union (EU) levels (Section IV) are assessed, showing how they may undermine a core human right by curtailing freedom of expression. Then, starting from the premise of social media as a “watchdog” of democracy and moving on to the contention that fake news is a phenomenon of “mature” democracy, the article argues that public law already protects freedom of expression and ensures its effectiveness at the international and EU levels through some fundamental rules (Section V). There follows a discussion of the key regulatory approaches, and, as alternatives to government intervention, self-regulation and especially empowering users are proposed as strategies to effectively manage fake news by mitigating the risks of undue interference by regulators in the right to freedom of expression (Section VI). The article concludes by offering some remarks on the proposed solution and in particular by recommending the implementation of reliability ratings on social media platforms (Section VII).

Chronic isolation of carotid sinus baroreceptor region in conscious normotensive and hypertensive rats

1998 ◽  
Vol 275 (1) ◽  
pp. H322-H329 ◽  
Author(s):  
Kelly P. McKeown ◽  
Artin A. Shoukas
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Arterial Pressure ◽  
Carotid Sinus ◽  
Baroreceptor Reflex ◽  
Hypertensive Rats ◽  
Conscious Rat ◽  
Sd Rats ◽  
The Right ◽  
Reflex System

We have developed a chronic technique to isolate the carotid sinus baroreceptor region in the conscious rat model. Our technique, when used in conjunction with other methods, allows for the study of the control of arterial pressure, heart rate, and cardiac output by the carotid sinus baroreceptor reflex in conscious, unrestrained rats. The performance of our technique was evaluated in two strains: normotensive Sprague-Dawley (SD) rats and spontaneously hypertensive rats (SHR). Each rat was instrumented with an aortic flow probe and a catheter placed in the right femoral artery to monitor cardiac output and arterial pressure, respectively. The cervical sympathetic trunk and aortic depressor nerve were ligated and cut bilaterally, leaving vagus nerves intact. The right and left carotid sinuses were isolated using our new technique. We tested the open-loop function of the carotid sinus baroreceptor reflex system in the conscious rat after recovery from the isolation surgery. We found that changes in nonpulsatile carotid sinus pressure caused significant changes in arterial pressure, heart rate, and total peripheral resistance in both rat strains. However, the cardiac output responses differed dramatically between strains. Significant changes were seen in the cardiac output response of SHR, whereas no significant changes were observed in normotensive SD rats. We have found this technique to be a highly reliable tool for the study of the carotid sinus baroreceptor reflex system in the conscious rat.

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