In physiological conditions, the cardiovascular system (CVS) is a closed circulatory system comprising a pump (the heart), a conduit system (vasculature), and a continuum media (blood) moving through the system. The heart is a major source of energy in this system. It pumps the blood through the two connected loops. From the mechanical point of view, CVS can be represented as a network of flexible tubes filled with a viscous incompressible fluid driven by a periodic energy source. The fluid dynamics are described by Navier-Stokes's equations, representing the fundamental physical principles of mass and momentum conservation. These equations allow computation of the blood velocity field and pressure depending on the forces exerted to the fluid's surface (surface forces) and to a unit portion of the fluid (mass forces). Equations of structural dynamics describe the motion of the vascular wall. The state-of-the-art models incorporate fluid and structure interaction (FSI). The blood flow in various parts of CVS has different features that must be considered during computational simulations. Elastic properties of the veins and arteries are different. The structural features of veins (valves) limit the backward flow. The geometry of venous cross-sections may be circular, elliptic, and dumbbell-shaped. It changes the flow characteristics. Blood rheology plays a significant role in venous flows. According to the mass conservation law, the work of the heart pump provides energy for the arterial flow and determines venous return to the heart atria. Venous hemodynamics comprises a lot of various processes with different physical and biological origins. Complex analysis of a patient requires computational simulations, which provide medical experts with a basis for prognosis and optimal surgical treatment. In this work, we review basic physical principles and modern mathematical models of venous hemodynamics. In conclusion, the blood flow in veins can be considered as a mechanical process. It obeys the fundamental physical principles and can be described by the well-known mathematical models of continuum mechanics. Thus, the flow characteristics can be simulated and predicted in various healthy and pathological conditions basing on the boundary conditions and material properties of the blood and veins.
{"title":"Physical principles of venous hemodynamics and its mathematical modeling","authors":"R. Tauraginskii, S. Simakov, F. Lurie, D. Borsuk","doi":"10.24019/jtavr.118","DOIUrl":"https://doi.org/10.24019/jtavr.118","url":null,"abstract":"In physiological conditions, the cardiovascular system (CVS) is a closed circulatory system comprising a pump (the heart), a conduit system (vasculature), and a continuum media (blood) moving through the system. The heart is a major source of energy in this system. It pumps the blood through the two connected loops. From the mechanical point of view, CVS can be represented as a network of flexible tubes filled with a viscous incompressible fluid driven by a periodic energy source. The fluid dynamics are described by Navier-Stokes's equations, representing the fundamental physical principles of mass and momentum conservation. These equations allow computation of the blood velocity field and pressure depending on the forces exerted to the fluid's surface (surface forces) and to a unit portion of the fluid (mass forces). Equations of structural dynamics describe the motion of the vascular wall. The state-of-the-art models incorporate fluid and structure interaction (FSI). The blood flow in various parts of CVS has different features that must be considered during computational simulations. Elastic properties of the veins and arteries are different. The structural features of veins (valves) limit the backward flow. The geometry of venous cross-sections may be circular, elliptic, and dumbbell-shaped. It changes the flow characteristics. Blood rheology plays a significant role in venous flows. According to the mass conservation law, the work of the heart pump provides energy for the arterial flow and determines venous return to the heart atria. Venous hemodynamics comprises a lot of various processes with different physical and biological origins. Complex analysis of a patient requires computational simulations, which provide medical experts with a basis for prognosis and optimal surgical treatment. In this work, we review basic physical principles and modern mathematical models of venous hemodynamics. In conclusion, the blood flow in veins can be considered as a mechanical process. It obeys the fundamental physical principles and can be described by the well-known mathematical models of continuum mechanics. Thus, the flow characteristics can be simulated and predicted in various healthy and pathological conditions basing on the boundary conditions and material properties of the blood and veins.","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84700093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The hemodynamic assessment of the bidirectional flow within calf perforators and in the conductive veins in varicose vein disease is presented. The bidirectional streaming within calf perforators is induced by the changing polarity of the systolic and diastolic pressure gradients arising during calf pump activity between the deep veins and the saphenous system of the lower leg, as documented by simultaneous pressure measurements in the posterior tibial vein and the great saphenous vein. This bidirectional flow makes the deep and superficial veins of the lower leg conjoined vessels. The vector of the bidirectional streaming in varicose vein patients is oriented inward, into the deep veins. The enlarged calf perforators are the consequence of the saphenous reflux; after elimination of saphenous reflux the diameter of calf perforators diminishes significantly. Results of venous pressure, plethysmographic and electromagnetic flow measurements rebut the still prevalent opinion that the outward flow within calf perforators is a reflux. There is an up-and-down flow in the conductive veins during calf pump activity with a prevailing systolic centripetal (orthograde) flow in the popliteal/femoral axis and a diastolic centrifugal (retrograde) flow in the incompetent great saphenous vein. The popliteal vein represents actually the drain pipe of the calf muscle pump. The ambulatory venous pressure gradient arising during the diastolic phase of the calf pump activity resembles the diastolic pressure difference between the aorta and the left ventricle.
{"title":"The hemodynamic impact of the bidirectional flow within calf perforators and conductive veins in varicose vein disease","authors":"C. Recek","doi":"10.24019/jtavr.101","DOIUrl":"https://doi.org/10.24019/jtavr.101","url":null,"abstract":"The hemodynamic assessment of the bidirectional flow within calf perforators and in the conductive veins in varicose vein disease is presented. The bidirectional streaming within calf perforators is induced by the changing polarity of the systolic and diastolic pressure gradients arising during calf pump activity between the deep veins and the saphenous system of the lower leg, as documented by simultaneous pressure measurements in the posterior tibial vein and the great saphenous vein. This bidirectional flow makes the deep and superficial veins of the lower leg conjoined vessels. The vector of the bidirectional streaming in varicose vein patients is oriented inward, into the deep veins. The enlarged calf perforators are the consequence of the saphenous reflux; after elimination of saphenous reflux the diameter of calf perforators diminishes significantly. Results of venous pressure, plethysmographic and electromagnetic flow measurements rebut the still prevalent opinion that the outward flow within calf perforators is a reflux. There is an up-and-down flow in the conductive veins during calf pump activity with a prevailing systolic centripetal (orthograde) flow in the popliteal/femoral axis and a diastolic centrifugal (retrograde) flow in the incompetent great saphenous vein. The popliteal vein represents actually the drain pipe of the calf muscle pump. The ambulatory venous pressure gradient arising during the diastolic phase of the calf pump activity resembles the diastolic pressure difference between the aorta and the left ventricle.","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87856251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alberto Alberto, D. Bissacco, S. Oberto, G. Bergamo, D. Kontothanassis, G. Mosti
Introduction: The common belief about the beneficial effects of water immersion on leg veins function is mostly based on empirical experiences. We have performed a series of tests to evaluate the real effects of the increase of interstitial pressure generated by water immersion on the leg veins morphology, venous return and veno-lymphatic drainage. Methods: The immediate effects of water hydrostatic pressure (wHP) on vein morphology and venous flow were evaluated by underwater duplex sonography (DS) during immersion. The immediate effects of HP on calf volume and ejection fraction (EF) were evaluated by underwater strain gauge pletysmography (SGP). The effects of prolonged immersion on leg volume and on subcutaneous tissues were evaluated by both water displacement volumetry (WDV) and DS. Results: The caliper of normal and varicose veins were immediately and significantly reduced by immersion (p.004 and p 0.012 for the femoral and great saphenous veins, respectively). Simultaneously, the spontaneous centripetal flow increased. In varicose legs, the reflux was reduced or even disappeared. SGP demonstrated an immediate reduction of the calf circumference and the simultaneous increase of the EF (+68.9%). Finally, a marked reduction in ankle circumference (-2.89%), subcutaneous tissue thickness (-24.35%) and leg volume (-4,2%) was demonstrated after 30’ of standing into the water. Walking into the pool for the same time resulted in an even more significant reduction of all these three parameters (-5.98%; -32.66% and -6.50%, respectively). Discussion: our results suggest that the wHP-related reduction of vein caliber is responsible for the immediate increase of the centripetal flow, the immediate reduction of the calf volume and of the reduced reflux, when present. The great reduction of the leg volume after prolonged static immersion seems to be due to the positive effects of wHP on the balance between interstitial fluid filtration and lymphatic reabsorption. A mutual enhancement between the effects of HP on interstitial fluids dynamics and those of muscle activity on EF, may explain the greater reduction of the leg volume, ankle circumference and epifascial thickness after underwater walking compared to those after static immersion. Conclusions: The possible clinical and rehabilitative implications of these findings in the treatment and rehabilitation of leg venous disorders are finally outlined.
{"title":"The effects of water immersion on venous return","authors":"Alberto Alberto, D. Bissacco, S. Oberto, G. Bergamo, D. Kontothanassis, G. Mosti","doi":"10.24019/jtavr.113","DOIUrl":"https://doi.org/10.24019/jtavr.113","url":null,"abstract":"Introduction: The common belief about the beneficial effects of water immersion on leg veins function is mostly based on empirical experiences. We have performed a series of tests to evaluate the real effects of the increase of interstitial pressure generated by water immersion on the leg veins morphology, venous return and veno-lymphatic drainage. Methods: The immediate effects of water hydrostatic pressure (wHP) on vein morphology and venous flow were evaluated by underwater duplex sonography (DS) during immersion. The immediate effects of HP on calf volume and ejection fraction (EF) were evaluated by underwater strain gauge pletysmography (SGP). The effects of prolonged immersion on leg volume and on subcutaneous tissues were evaluated by both water displacement volumetry (WDV) and DS. Results: The caliper of normal and varicose veins were immediately and significantly reduced by immersion (p.004 and p 0.012 for the femoral and great saphenous veins, respectively). Simultaneously, the spontaneous centripetal flow increased. In varicose legs, the reflux was reduced or even disappeared. SGP demonstrated an immediate reduction of the calf circumference and the simultaneous increase of the EF (+68.9%). Finally, a marked reduction in ankle circumference (-2.89%), subcutaneous tissue thickness (-24.35%) and leg volume (-4,2%) was demonstrated after 30’ of standing into the water. Walking into the pool for the same time resulted in an even more significant reduction of all these three parameters (-5.98%; -32.66% and -6.50%, respectively). Discussion: our results suggest that the wHP-related reduction of vein caliber is responsible for the immediate increase of the centripetal flow, the immediate reduction of the calf volume and of the reduced reflux, when present. The great reduction of the leg volume after prolonged static immersion seems to be due to the positive effects of wHP on the balance between interstitial fluid filtration and lymphatic reabsorption. A mutual enhancement between the effects of HP on interstitial fluids dynamics and those of muscle activity on EF, may explain the greater reduction of the leg volume, ankle circumference and epifascial thickness after underwater walking compared to those after static immersion. Conclusions: The possible clinical and rehabilitative implications of these findings in the treatment and rehabilitation of leg venous disorders are finally outlined.","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77965760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Invited commentary on 'Venous return simplified with air-plethysmography, modelling and Sack Theory' by CR Lattimer, A Obermayer","authors":"C. Franceschi","doi":"10.24019/jtavr.110","DOIUrl":"https://doi.org/10.24019/jtavr.110","url":null,"abstract":"","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73976156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Invited commentary on 'The hemodynamic impact of the bidirectional flow within calf perforators and conductive veins in varicose vein disease', by C Recek","authors":"S. Ricci","doi":"10.24019/jtavr.103","DOIUrl":"https://doi.org/10.24019/jtavr.103","url":null,"abstract":"","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87467987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Franceschi, M. Cappelli, J. M. Escribano, E. Mendoza
Dynamic Fractioning of the Gravitational Hydrostatic Pressure (DFGHSP) is a pillar of a hemodynamic model of the venous pathophysiology. It describes how the valvo-muscular pump varies the distal venous pressure in the lower limbs. It results from an inductive reasoning based on clinical signs and instrumental data at rest and during the action of the valvo-muscular pump of the calf. It does not claim to be the final truth, but a new "as if" model that improved the diagnosis and the treatment of the venous insufficiency (CHIVA, French acronym for Cure Conservatrice et Hémodynamique de l’Insuffisance Veineuse en Ambulatoire) according to several randomized studies and meta-analyses. That approach overturns the classic diagnosis and treatment of venous insufficiency because it is conservative and opposes the widely spread destructive based view. It needs a minimal study of basic fluid mechanics which can explain venous hemodynamics, the core of venous pathophysiology. The proposed DFGHSP fluid mechanics model is compared with the hemodynamic clinical and instrumental data in order to assess its pathophysiologic relevance.
重力静水压力的动态分馏(DFGHSP)是静脉病理生理的血流动力学模型的支柱。它描述了瓣膜-肌肉泵如何改变下肢远端静脉压力。它是基于临床症状和仪器数据的归纳推理的结果，在休息和小腿瓣膜肌肉泵的作用期间。这并不是最终的真理，而是一种新的“好像”模型，根据几项随机研究和荟萃分析，它改善了静脉功能不全的诊断和治疗(CHIVA，法语为Cure Conservatrice et hsammodynamique del 'Insuffisance Veineuse en Ambulatoire的首字母缩写)。该方法推翻了静脉功能不全的经典诊断和治疗，因为它是保守的，反对广泛传播的基于破坏性的观点。它需要对基础流体力学进行最低限度的研究，以解释静脉血流动力学，这是静脉病理生理的核心。将DFGHSP流体力学模型与血流动力学临床和仪器数据进行比较，以评估其病理生理相关性。
{"title":"Dynamic Fractioning of the Gravitational Hydrostatic Pressure: A hemodynamic model for the venous pressure control by the valvo-muscular pump","authors":"C. Franceschi, M. Cappelli, J. M. Escribano, E. Mendoza","doi":"10.24019/JTAVR.100","DOIUrl":"https://doi.org/10.24019/JTAVR.100","url":null,"abstract":"Dynamic Fractioning of the Gravitational Hydrostatic Pressure (DFGHSP) is a pillar of a hemodynamic model of the venous pathophysiology. It describes how the valvo-muscular pump varies the distal venous pressure in the lower limbs. It results from an inductive reasoning based on clinical signs and instrumental data at rest and during the action of the valvo-muscular pump of the calf. It does not claim to be the final truth, but a new \"as if\" model that improved the diagnosis and the treatment of the venous insufficiency (CHIVA, French acronym for Cure Conservatrice et Hémodynamique de l’Insuffisance Veineuse en Ambulatoire) according to several randomized studies and meta-analyses. That approach overturns the classic diagnosis and treatment of venous insufficiency because it is conservative and opposes the widely spread destructive based view. It needs a minimal study of basic fluid mechanics which can explain venous hemodynamics, the core of venous pathophysiology. The proposed DFGHSP fluid mechanics model is compared with the hemodynamic clinical and instrumental data in order to assess its pathophysiologic relevance.","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81158353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since 1980 using the Doppler method, planned by Bartolo, we have studied several patients by means of the measurement of venous pressures, both in orthostatism and in clinostatism. In a normal subject, in orthostatism the value of average pressure is 60 mmHg in the posterior tibial vein, and 60 mmHg in the long saphenous vein. When there are varicose veins, the average pressure is 90 and 96 mmHg respectively in the deep veins and in the superficial ones. In the case of post-thrombotic syndrome, the average values are 101 and 102 mmHg in the deep and superficial veins, respectively. In clinostatism, the normal values are under 20 mmHg and in subjects with vein thrombosis the value increase to 30 mmHg and more. After more than 30 years we discuss the reliability of the method, the hemodynamic basis and its clinical application in phlebological practice.
{"title":"The measurement of venous pressure by Doppler: is it a hemodynamic evaluation ?","authors":"P. Antignani, G. Peruzzi, T. Spina","doi":"10.24019/jtavr.114","DOIUrl":"https://doi.org/10.24019/jtavr.114","url":null,"abstract":"Since 1980 using the Doppler method, planned by Bartolo, we have studied several patients by means of the measurement of venous pressures, both in orthostatism and in clinostatism. In a normal subject, in orthostatism the value of average pressure is 60 mmHg in the posterior tibial vein, and 60 mmHg in the long saphenous vein. When there are varicose veins, the average pressure is 90 and 96 mmHg respectively in the deep veins and in the superficial ones. In the case of post-thrombotic syndrome, the average values are 101 and 102 mmHg in the deep and superficial veins, respectively. In clinostatism, the normal values are under 20 mmHg and in subjects with vein thrombosis the value increase to 30 mmHg and more. After more than 30 years we discuss the reliability of the method, the hemodynamic basis and its clinical application in phlebological practice.","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91339889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The usual mantra taught by experts is to explain venous return using (i) pressure gradients, (ii) ankle joint movements and (iii) the suction effect of inspiration. This is supported with data obtained directly from venous pressure measurements and indirectly using ultrasound calculations. Whilst these veno-dynamic factors undoubtedly assist in the venous return process, the primary mechanism is missing from the standard teaching curriculum. Evidence for this is the observation that most patients with calf muscle pump (CMP) inactivity or failure of active inspiration have an excellent venous return. Examples include persons on mechanical ventilation, in a wheelchair from paralysis or amputees. Chair sleeping is another example. The first strategy of this paper is to explain venous return using calf volume changes in response to gravitational positioning. It relies on the premise that arterial supply volume equals venous drainage volume. When this system is challenged by gravitational positioning, the resulting calf volume changes demand an explanation in terms of an inequality in the inflow = outflow hypothesis. Large volume shifts illustrate the powerful ability of gravity to change venous drainage dynamics. The second strategy is to use modelling with water, beakers, bags and tubes to explain upward flow against hydrostatic columns over a metre high. Whilst this is a data free exercise, the experiments are easily repeatable and understandable. They will depict pressure using height instead of pressure transducers (which are themselves calibrated using liquid columns). Most important, it will demonstrate that pressure is not the cause of the flow but the expression of the feature of a hydrodynamic system. The final strategy is to place Sack Theory into context as the hidden environment making venous drainage possible. It relies on the fact that our bodies are made of collapsible “sacks”, liquids and tissues that compress like liquids. These are surrounded by a hierarchy of enveloping membranes with each absorbing their enclosed weight and transferring their contents into weightless tissue. Once transformed, gravitational forces are negated making upward flow energy efficient. Collapsible venous drainage tubes are recognised as one such envelope (sack). Elementary child-friendly models are illustrated, and the role of trans-membrane pressure neutralisation is highlighted. Veno-dynamic equations will not be used.
{"title":"Venous return simplified with air-plethysmography, modelling and Sack Theory","authors":"C. Lattimer, A. Obermayer","doi":"10.24019/jtavr.109","DOIUrl":"https://doi.org/10.24019/jtavr.109","url":null,"abstract":"The usual mantra taught by experts is to explain venous return using (i) pressure gradients, (ii) ankle joint movements and (iii) the suction effect of inspiration. This is supported with data obtained directly from venous pressure measurements and indirectly using ultrasound calculations. Whilst these veno-dynamic factors undoubtedly assist in the venous return process, the primary mechanism is missing from the standard teaching curriculum. Evidence for this is the observation that most patients with calf muscle pump (CMP) inactivity or failure of active inspiration have an excellent venous return. Examples include persons on mechanical ventilation, in a wheelchair from paralysis or amputees. Chair sleeping is another example. The first strategy of this paper is to explain venous return using calf volume changes in response to gravitational positioning. It relies on the premise that arterial supply volume equals venous drainage volume. When this system is challenged by gravitational positioning, the resulting calf volume changes demand an explanation in terms of an inequality in the inflow = outflow hypothesis. Large volume shifts illustrate the powerful ability of gravity to change venous drainage dynamics. The second strategy is to use modelling with water, beakers, bags and tubes to explain upward flow against hydrostatic columns over a metre high. Whilst this is a data free exercise, the experiments are easily repeatable and understandable. They will depict pressure using height instead of pressure transducers (which are themselves calibrated using liquid columns). Most important, it will demonstrate that pressure is not the cause of the flow but the expression of the feature of a hydrodynamic system. The final strategy is to place Sack Theory into context as the hidden environment making venous drainage possible. It relies on the fact that our bodies are made of collapsible “sacks”, liquids and tissues that compress like liquids. These are surrounded by a hierarchy of enveloping membranes with each absorbing their enclosed weight and transferring their contents into weightless tissue. Once transformed, gravitational forces are negated making upward flow energy efficient. Collapsible venous drainage tubes are recognised as one such envelope (sack). Elementary child-friendly models are illustrated, and the role of trans-membrane pressure neutralisation is highlighted. Veno-dynamic equations will not be used.","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78594328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Answers to the invited commentaries on 'Venous return simplified with air-plethysmography, modelling and Sack Theory' by CR Lattimer, A Obermayer","authors":"C. Lattimer, A. Obermayer","doi":"10.24019/jtavr.112","DOIUrl":"https://doi.org/10.24019/jtavr.112","url":null,"abstract":"","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84794515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Invited commentary on 'Venous return simplified with air-plethysmography, modelling and Sack Theory' by CR Lattimer, A Obermayer","authors":"E. Mendoza","doi":"10.24019/jtavr.111","DOIUrl":"https://doi.org/10.24019/jtavr.111","url":null,"abstract":"","PeriodicalId":17406,"journal":{"name":"Journal of Theoretical and Applied Vascular Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87195552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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