{"id":21,"date":"2011-01-01T18:23:05","date_gmt":"2011-01-01T17:23:05","guid":{"rendered":"http:\/\/schueler.ws\/wordpress\/?page_id=21"},"modified":"2026-02-12T01:00:18","modified_gmt":"2026-02-12T00:00:18","slug":"vvp-2","status":"publish","type":"page","link":"http:\/\/schueler.ws\/en\/artikel\/medizinische-themen\/vvp-2\/","title":{"rendered":"(Deutsch) VVP (2)"},"content":{"rendered":"<p>Ralf Sch\u00fcler<br \/>\n  <a href=\"https:\/\/robohand.net\/models\/beautifulstranger64\" target=\"_blank\">inst beautifulstranger64<\/a><\/p>\n<h1>IMPROVING THE ACCURACY OF VENOUS OCCLUSION PLETHYSMOGRAPHY WITH IMPEDANCE METHOD<\/h1>\n<p><em> Proceedings of the IX. International Conference on electrical Bio-Impedance,<br \/>\nHeidelberg 1995, pp. 295 <\/em><\/p>\n<p><em>In the tracings of venous occlusion plethysmograhy (VOP) there is a  spike immediatelly after releasing the pneumatic occlusion cuffs. This  spike only occures if the measurment of the blood volume is done via  bio-impedance not via other measurment methods. This study investigates  the origin of this spike and the error it produces. This was done by  observing practical examinations with the measurement system rheoscreen\u00ae  as well as by mathematical modelling. It could be found that there are  large interindividual differences in the occurence of this spike. Often  it is very small but sometimes it produces significant errors. To solve  this problem we developed a method to eliminate the effects of the spike  and integrated the method in the measuring system rheoscreen\u00ae to reach  better diagnostic validity in such cases. <\/em><\/p>\n<h2>Introduction<\/h2>\n<p>The venous occlusion plethysmography (VOP) is a widespread  method for diagnosing deep vein thrombosis. The method is to obstruct  the venous outflow by a pneumatic cuff while arterial inflow continues  because of the higher arterial pressure. The veins fills with blood.  After some minutes the cuffs were released quickly. The speed of  outflowing blood is significantly reduced in case of an outflow  obstruction like a thrombosis. One method to measure limb blood volume  changes under VOP is the use of electrical bio-impedance. Fig. 1 shows a  typical VOP-tracing. Please note, that the impedance is indirect  proportional to the blood volume (decrease blood volume means increase  impedance). In case of modern equipment the bio-impedance method  detecting blood volume changes is highly sensitive and easy to handle.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/www.schueler.ws\/img\/heidelb1.gif\" border=\"0\" alt=\"\" width=\"600\" height=\"325\" \/><br \/>\n<span>Fig1: Typical impedance tracing during VOP<\/span><\/p>\n<p>But in contrast to other methods like strain gauge there is a  spike in the impedance signal immediately after opening the occlusion  cuff. Mohapatra (1) described this as the effect of changing blood  resistivity by changing the blood velocity. Any authors don\u00b4t notify the presence of this effect, other (3) describe  this as a source of a large error.<\/p>\n<p>Our study analyses the effect of the mentioned spike on the accuracy of the impedance method.<\/p>\n<h2>Materials and Methods<\/h2>\n<h3>Practical Investigations<\/h3>\n<p>We determined the size of the spike by analysing the data of  about 200 medical routine examinations with the angiologic measuring  system rheoscreen\u00ae. We evaluate the height of the spike in relation of  the total amplitude (also called &#8220;venous capacitance&#8221;) of the VOP-curve.<\/p>\n<h3>Mathematical Modelling<\/h3>\n<p>A mathematical model of the blood outflow in the limbs after  venous occlusion was used to confirm the genesis of the spike by changes  of blood resistivity and to show the kind of errors produced by this  effect. A mathematical model is necessary to evaluate this because of  practical measurements with different measuring methods are not usable.  The error caused by a comparision of different measurement methods is  normaly higher then the error caused by the spike.<\/p>\n<p>We used a blood flow model of the limb that was originate  used to evaluate the influence of various factors like measurement  conditions and various physiological changes of the shape of the outflow  curve obtained by the VOP. To consider the blood resistivity we expand  the model with the dependency of the blood resistivity on the blood  velocity (2).<\/p>\n<p>The model considers the following factors:<\/p>\n<ul>\n<li> the resting volume of the veins<\/li>\n<li> the nonlinear dependency of the venous compliance on the venous pressure<\/li>\n<li> the different hydrostatic pressure in different sections<\/li>\n<li> the arterial inflow<\/li>\n<li> the flow resistance of the venous system<\/li>\n<\/ul>\n<p>The physiological constants used in the model can be found in (4,  5). The model requires an iterative computation to solve the equation  system. The calculations of the simulations were done at a Pentium-PC.<\/p>\n<p>The model doesn\u00b4t consider the phase in which the cuff is  just opening. That\u00b4s why it isn\u00b4t possible to simulate the shape of the  spike.<\/p>\n<h2>Results<\/h2>\n<h3>Practical investigations<\/h3>\n<p>There are large interindividual differences in the spike  amplitude. The spike could be found in nearly all observed examinations.  In most cases (approx. 80%) the spike was very little (below 5%). Only  in approx. 5% the spike has an amplitude of greater then 25% of the  venous capacitance. It was found that the spikes in patients with any  kind of outflow obstructions was more often higher. This is caused by  the low venous capacitance in this group as well as by an increase of  the total amplitude. Because of the very large interindividual  differences there is no rule to consider this by the evaluation of the  measuring results.<\/p>\n<h3>Model<\/h3>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/www.schueler.ws\/img\/heidelb2.gif\" border=\"0\" alt=\"\" width=\"530\" height=\"309\" \/><br \/>\n<span>Fig 2: Graphical results of the mathematical simulation<\/span><\/p>\n<p>The mathematical model corresponds good with the practical  results. The simulated outflow curve shows a high conformity with real  obtained curves. The results show clearly the difference between  simulating the volume changes after opening the venous occlusion with  and without the dependence of blood resistivity on blood velocity. The  variation of the blood resistivity cause a higher curve level. The error  is as higher as faster the blood flows out. This means that the highest  error occured immediately after opening the cuff.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/www.schueler.ws\/img\/heidelb3.gif\" border=\"0\" alt=\"\" width=\"450\" height=\"190\" \/><br \/>\n<span>Fig 3: Two possibilities to measure outflow volume<\/span><\/p>\n<h3>Effect of the calculation of diagnostically relevant parameters<\/h3>\n<p>To diagnose venous outflow obstructions such as thrombosis  there are used the amount of blood flowing out two, three or five  seconds after opening the venous occlusion. Figure 3 illustrates two  possible ways to determine this levels from the top of the spike or from  the level before opening. For the first method the error is small or  nearly zero immediately after opening the cuffs and largest after  reaching the resting level. The error trend of the second method is  opposite. That\u00b4s why the first method should be preffered to calculate  the blood outflow in the first time and the second method to calculate  the total amount of blood flowing out. In most cases this should reduce  the error to a low level.<\/p>\n<p>But in cases of low venous capacitance and relative high spikes the  error reaches a level that can cause poor interpretations of the  measuring results. Data from thrombosis can be interpreted as borderline  values.  To avoid this it is necessary to eliminate the effect of  varying blood resistivity by the evaluation software. This can be done  by measuring the outflow velocity to correct the curve in dependence on  the spike height on basis of the relations we used in the model.<\/p>\n<h2>Conclusions<\/h2>\n<p>The measurement of blood volume changes under VOP by  bio-impedance is a highly sensitive method. But the dependence of the  blood resistivity on the blood velocity may sometimes cause a high error  level especially in cases of outflow obstructions. Therefore this  effect has to be eliminated to calculate precise parameters. We  developed a method to do this and implemented it in the angiologic  diagnostic system rheoscreen\u00ae. So the bio-impedance becomes a highly  sensitive mesuring method with no loss of accuracy by impedance specific  effects.<\/p>\n<h2>References<\/h2>\n<p>1.  Surya N. Mohapatra<br \/>\nNon-invasive Cardiovascular Monitoring by Electrical Impedance Technique<br \/>\nPitman Medical 1981<\/p>\n<p>2.        Lamberts, R.<br \/>\nImpedance Cardiography<br \/>\nDiss. Uni Gorcum 1984<\/p>\n<p>3.        G. Rudofsky, J. Gutmann, M. Althoff<br \/>\nApparative Gef\u00e4\u00dfdiagnostik mit Doppler, Duplex, Verschlu\u00df-Plethysmograf und Lichtreflex-Plethysmograf<br \/>\nEurasburger Berichte zu Themen der Angiologie und Kardiologie, Heft 7, 1993<\/p>\n<p>4.        Rudi Busse<br \/>\nKreislaufphysiologie<br \/>\nGeorg Thieme Verlag Stuttgart, New York, 1982<\/p>\n<p>5.        D. H. Bergel<br \/>\nThe static elastic properties of the of the arterial wall<br \/>\nJ. Physiol. 156 (1961), S. 455-457<\/p>\n<p>6.        T. M. Ravi Shankar, John G. Webster, Shu-Yong Shao<br \/>\nThe Contribution of Vessel Volume Change and Blood Resistivity Change to the Electrical Impedance Pulse<br \/>\nIEEE Transactions on Biomedical Engineering, Vol. 33, 3\/1985<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Ralf Sch\u00fcler inst beautifulstranger64 IMPROVING THE ACCURACY OF VENOUS OCCLUSION PLETHYSMOGRAPHY WITH IMPEDANCE METHOD Proceedings of the IX. International Conference on electrical Bio-Impedance, Heidelberg 1995, pp. 295 In the tracings of venous occlusion plethysmograhy (VOP) there is a spike immediatelly &hellip; <a href=\"http:\/\/schueler.ws\/en\/artikel\/medizinische-themen\/vvp-2\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":84,"menu_order":4,"comment_status":"open","ping_status":"closed","template":"","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","ngg_post_thumbnail":0,"footnotes":""},"class_list":["post-21","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/schueler.ws\/en\/wp-json\/wp\/v2\/pages\/21","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/schueler.ws\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/schueler.ws\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/schueler.ws\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/schueler.ws\/en\/wp-json\/wp\/v2\/comments?post=21"}],"version-history":[{"count":0,"href":"http:\/\/schueler.ws\/en\/wp-json\/wp\/v2\/pages\/21\/revisions"}],"up":[{"embeddable":true,"href":"http:\/\/schueler.ws\/en\/wp-json\/wp\/v2\/pages\/84"}],"wp:attachment":[{"href":"http:\/\/schueler.ws\/en\/wp-json\/wp\/v2\/media?parent=21"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}