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class="vector-toc-numb">2</span> <span>Units for measuring</span> </div> </a> <ul id="toc-Units_for_measuring-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Calculation" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Calculation"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Calculation</span> </div> </a> <button aria-controls="toc-Calculation-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Calculation subsection</span> </button> <ul id="toc-Calculation-sublist" class="vector-toc-list"> <li id="toc-Systemic_vascular_resistance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Systemic_vascular_resistance"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Systemic vascular resistance</span> </div> </a> <ul id="toc-Systemic_vascular_resistance-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Peripheral_vascular_resistance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Peripheral_vascular_resistance"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Peripheral vascular resistance</span> </div> </a> <ul id="toc-Peripheral_vascular_resistance-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Regulation" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Regulation"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Regulation</span> </div> </a> <button aria-controls="toc-Regulation-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Regulation subsection</span> </button> <ul 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resistance</a>)</span></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Force from blood vessels that affects blood flow</div> <p><b>Vascular resistance</b> is the resistance that must be overcome for <a href="/wiki/Blood" title="Blood">blood</a> to flow through the <a href="/wiki/Circulatory_system" title="Circulatory system">circulatory system</a>. The resistance offered by the systemic circulation is known as the <b>systemic vascular resistance</b> or may sometimes be called by another term <b>total peripheral resistance</b>, while the resistance caused by the <a href="/wiki/Pulmonary_circulation" title="Pulmonary circulation">pulmonary circulation</a> is known as the <b>pulmonary vascular resistance</b>. <a href="/wiki/Vasoconstriction" title="Vasoconstriction">Vasoconstriction</a> (i.e., decrease in the diameter of <a href="/wiki/Artery" title="Artery">arteries</a> and <a href="/wiki/Arteriole" title="Arteriole">arterioles</a>) increases resistance, whereas <a href="/wiki/Vasodilation" title="Vasodilation">vasodilation</a> (increase in diameter) decreases resistance. <a href="/wiki/Blood_flow" class="mw-redirect" title="Blood flow">Blood flow</a> and <a href="/wiki/Cardiac_output" title="Cardiac output">cardiac output</a> are related to <a href="/wiki/Blood_pressure" title="Blood pressure">blood pressure</a> and inversely related to vascular resistance. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Measurement">Measurement</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=1" title="Edit section: Measurement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The measurement of vascular resistance is challenging in most situations. The standard method is by the use of a <a href="/wiki/Pulmonary_artery_catheter" title="Pulmonary artery catheter">Pulmonary artery catheter</a>. This is common in ICU settings but impractical is most other settings. </p> <div class="mw-heading mw-heading2"><h2 id="Units_for_measuring">Units for measuring</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=2" title="Edit section: Units for measuring"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Units for measuring vascular resistance are <a href="/wiki/Dyne" title="Dyne">dyn</a>·s·cm<sup>−5</sup>, pascal seconds per cubic metre (Pa·s/m<sup>3</sup>) or, for ease of deriving it by pressure (measured in <a href="/wiki/MmHg" class="mw-redirect" title="MmHg">mmHg</a>) and <a href="/wiki/Cardiac_output" title="Cardiac output">cardiac output</a> (measured in L/min), it can be given in mmHg·min/L. This is numerically equivalent to hybrid resistance units (HRU), also known as Wood units (in honor of <a href="/wiki/Paul_Hamilton_Wood" title="Paul Hamilton Wood">Paul Wood</a>, an early pioneer in the field), frequently used by pediatric cardiologists. The conversion between these units is:<sup id="cite_ref-Fuster2004_1-0" class="reference"><a href="#cite_note-Fuster2004-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 1\,{\frac {{\text{mmHg}}\cdot {\text{min}}}{\text{ L }}}({\text{HRUs}})=8\,{\frac {{\text{MPa}}\cdot {\text{s}}}{{\text{m}}^{3}}}=80\,{\frac {{\text{dyn}}\cdot {\text{sec}}}{{\text{cm}}^{5}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mn>1</mn> <mspace width="thinmathspace" /> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mtext>mmHg</mtext> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mtext>min</mtext> </mrow> </mrow> <mtext> L </mtext> </mfrac> </mrow> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <mtext>HRUs</mtext> </mrow> <mo stretchy="false">)</mo> <mo>=</mo> <mn>8</mn> <mspace width="thinmathspace" /> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mtext>MPa</mtext> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mtext>s</mtext> </mrow> </mrow> <msup> <mrow class="MJX-TeXAtom-ORD"> <mtext>m</mtext> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> </msup> </mfrac> </mrow> <mo>=</mo> <mn>80</mn> <mspace width="thinmathspace" /> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mtext>dyn</mtext> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mtext>sec</mtext> </mrow> </mrow> <msup> <mrow class="MJX-TeXAtom-ORD"> <mtext>cm</mtext> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>5</mn> </mrow> </msup> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle 1\,{\frac {{\text{mmHg}}\cdot {\text{min}}}{\text{ L }}}({\text{HRUs}})=8\,{\frac {{\text{MPa}}\cdot {\text{s}}}{{\text{m}}^{3}}}=80\,{\frac {{\text{dyn}}\cdot {\text{sec}}}{{\text{cm}}^{5}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/54832a03233a90ee8574f45998f7cadb309e2336" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.171ex; width:50.715ex; height:5.676ex;" alt="{\displaystyle 1\,{\frac {{\text{mmHg}}\cdot {\text{min}}}{\text{ L }}}({\text{HRUs}})=8\,{\frac {{\text{MPa}}\cdot {\text{s}}}{{\text{m}}^{3}}}=80\,{\frac {{\text{dyn}}\cdot {\text{sec}}}{{\text{cm}}^{5}}}}"></span> </p> <table class="wikitable"> <tbody><tr> <th rowspan="2">Measurement </th> <th colspan="3">Reference range </th></tr> <tr> <th>dyn·s/cm<sup>5</sup></th> <th>MPa·s/m<sup>3</sup></th> <th>mmHg·min/L or <br /> HRU/Wood units </th></tr> <tr> <td>Systemic vascular resistance </td> <td>700–1600<sup id="cite_ref-WashingtonSurgery2008_2-0" class="reference"><a href="#cite_note-WashingtonSurgery2008-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></td> <td>70–160<sup id="cite_ref-dyn_3-0" class="reference"><a href="#cite_note-dyn-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></td> <td>9–20<sup id="cite_ref-dyn_3-1" class="reference"><a href="#cite_note-dyn-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>Pulmonary vascular resistance </td> <td>20–130<sup id="cite_ref-WashingtonSurgery2008_2-1" class="reference"><a href="#cite_note-WashingtonSurgery2008-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></td> <td>2–13<sup id="cite_ref-dyn_3-2" class="reference"><a href="#cite_note-dyn-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></td> <td>0.25–1.6<sup id="cite_ref-dyn_3-3" class="reference"><a href="#cite_note-dyn-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Calculation">Calculation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=3" title="Edit section: Calculation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In the hydraulic version of <a href="/wiki/Ohm%27s_law" title="Ohm's law">Ohm's law</a>, sometimes called Ohm’s law of fluid flow, vascular resistance is analogous to electrical resistance, the pressure difference is analogous to the electrical voltage difference, and volumetric flow is analogous to electric current flow:<sup id="cite_ref-:0_4-0" class="reference"><a href="#cite_note-:0-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R=\Delta P/Q}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>R</mi> <mo>=</mo> <mi mathvariant="normal">Δ</mi> <mi>P</mi> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mi>Q</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle R=\Delta P/Q}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0dc4162206ef892b0b7d986d00c05bbf8c9282e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:11.545ex; height:2.843ex;" alt="{\displaystyle R=\Delta P/Q}"></span></dd></dl> <p>where </p> <ul><li>R is resistance</li> <li>ΔP is the difference in pressure across the circulation loop (systemic / pulmonary) from its beginning (immediately after exiting the left ventricle / right ventricle) to its end (entering the right atrium / left atrium)</li> <li>Q is the flow through the vasculature (when discussing SVR this is equal to <a href="/wiki/Cardiac_output" title="Cardiac output">cardiac output</a>)</li></ul> <div class="mw-heading mw-heading3"><h3 id="Systemic_vascular_resistance">Systemic vascular resistance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=4" title="Edit section: Systemic vascular resistance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The SVR can therefore be calculated in units of dyn·s·cm<sup>−5</sup> as </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {80\cdot (mean\ arterial\ pressure-mean\ right\ atrial\ pressure)}{cardiac\ output}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>80</mn> <mo>⋅</mo> <mo stretchy="false">(</mo> <mi>m</mi> <mi>e</mi> <mi>a</mi> <mi>n</mi> <mtext> </mtext> <mi>a</mi> <mi>r</mi> <mi>t</mi> <mi>e</mi> <mi>r</mi> <mi>i</mi> <mi>a</mi> <mi>l</mi> <mtext> </mtext> <mi>p</mi> <mi>r</mi> <mi>e</mi> <mi>s</mi> <mi>s</mi> <mi>u</mi> <mi>r</mi> <mi>e</mi> <mo>−</mo> <mi>m</mi> <mi>e</mi> <mi>a</mi> <mi>n</mi> <mtext> </mtext> <mi>r</mi> <mi>i</mi> <mi>g</mi> <mi>h</mi> <mi>t</mi> <mtext> </mtext> <mi>a</mi> <mi>t</mi> <mi>r</mi> <mi>i</mi> <mi>a</mi> <mi>l</mi> <mtext> </mtext> <mi>p</mi> <mi>r</mi> <mi>e</mi> <mi>s</mi> <mi>s</mi> <mi>u</mi> <mi>r</mi> <mi>e</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>c</mi> <mi>a</mi> <mi>r</mi> <mi>d</mi> <mi>i</mi> <mi>a</mi> <mi>c</mi> <mtext> </mtext> <mi>o</mi> <mi>u</mi> <mi>t</mi> <mi>p</mi> <mi>u</mi> <mi>t</mi> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {80\cdot (mean\ arterial\ pressure-mean\ right\ atrial\ pressure)}{cardiac\ output}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/88c7600b0b6375f5567b93560a60a54af511650a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:60.744ex; height:6.176ex;" alt="{\displaystyle {\frac {80\cdot (mean\ arterial\ pressure-mean\ right\ atrial\ pressure)}{cardiac\ output}}}"></span></dd></dl> <p>where the pressures are measured in mmHg and the cardiac output is measured in units of <a href="/wiki/Litre" title="Litre">litres</a> per <a href="/wiki/Minute" title="Minute">minute</a> (L/min). <a href="/wiki/Mean_arterial_pressure" title="Mean arterial pressure">Mean arterial pressure</a> is the cycle average of blood pressure and is commonly approximated as 2 x diastolic blood pressure + systolic blood pressure/3 [or diastolic blood pressure + 1/3(systolic blood pressure - diastolic blood pressure)]. Mean right atrial pressure or <a href="/wiki/Central_venous_pressure" title="Central venous pressure">central venous pressure</a>, is usually very low (normally around 4mmHg), and as a result, it is frequently disregarded.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>As an example: if systolic blood pressure = 120 mmHg, diastolic blood pressure = 80 mmHg, right atrial mean pressure = 3 mmHg and cardiac output = 5 L/min, Then mean arterial pressure = 2 x diastolic pressure + systolic pressure/3 = 93.3 mmHg, and SVR = (93 - 3) / 5 = 18 Wood units, or equivalently 1440 dyn·s/cm<sup>5</sup>. </p><p>It is difficult to measure or monitor SVR in most locations outside the ICU. An invasive catheter is necessary. SVR, BP and CO are related to each other but only BP is easily measured. In the typical situation at the bedside we have an equation with three variables, one known, that is the BP and two unknown, CO and SVR. For this reason the BP is frequently used as a practical but somewhat inadequate definition of <a href="/wiki/Shock_(circulatory)" title="Shock (circulatory)">shock</a> or the state of blood flow. </p> <div class="mw-heading mw-heading3"><h3 id="Peripheral_vascular_resistance">Peripheral vascular resistance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=5" title="Edit section: Peripheral vascular resistance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The PVR can be calculated similarly (in units of dyn·s·cm<sup>−5</sup> ) as: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {80\cdot (mean\ pulmonary\ arterial\ pressure-mean\ pulmonary\ artery\ wedge\ pressure)}{cardiac\ output}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>80</mn> <mo>⋅</mo> <mo stretchy="false">(</mo> <mi>m</mi> <mi>e</mi> <mi>a</mi> <mi>n</mi> <mtext> </mtext> <mi>p</mi> <mi>u</mi> <mi>l</mi> <mi>m</mi> <mi>o</mi> <mi>n</mi> <mi>a</mi> <mi>r</mi> <mi>y</mi> <mtext> </mtext> <mi>a</mi> <mi>r</mi> <mi>t</mi> <mi>e</mi> <mi>r</mi> <mi>i</mi> <mi>a</mi> <mi>l</mi> <mtext> </mtext> <mi>p</mi> <mi>r</mi> <mi>e</mi> <mi>s</mi> <mi>s</mi> <mi>u</mi> <mi>r</mi> <mi>e</mi> <mo>−</mo> <mi>m</mi> <mi>e</mi> <mi>a</mi> <mi>n</mi> <mtext> </mtext> <mi>p</mi> <mi>u</mi> <mi>l</mi> <mi>m</mi> <mi>o</mi> <mi>n</mi> <mi>a</mi> <mi>r</mi> <mi>y</mi> <mtext> </mtext> <mi>a</mi> <mi>r</mi> <mi>t</mi> <mi>e</mi> <mi>r</mi> <mi>y</mi> <mtext> </mtext> <mi>w</mi> <mi>e</mi> <mi>d</mi> <mi>g</mi> <mi>e</mi> <mtext> </mtext> <mi>p</mi> <mi>r</mi> <mi>e</mi> <mi>s</mi> <mi>s</mi> <mi>u</mi> <mi>r</mi> <mi>e</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>c</mi> <mi>a</mi> <mi>r</mi> <mi>d</mi> <mi>i</mi> <mi>a</mi> <mi>c</mi> <mtext> </mtext> <mi>o</mi> <mi>u</mi> <mi>t</mi> <mi>p</mi> <mi>u</mi> <mi>t</mi> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {80\cdot (mean\ pulmonary\ arterial\ pressure-mean\ pulmonary\ artery\ wedge\ pressure)}{cardiac\ output}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7d1fd1f59727e16d0001552f6aad7aea250761e8" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:85.862ex; height:6.176ex;" alt="{\displaystyle {\frac {80\cdot (mean\ pulmonary\ arterial\ pressure-mean\ pulmonary\ artery\ wedge\ pressure)}{cardiac\ output}}}"></span></dd></dl> <p>where the units of measurement are the same as for SVR. The <a href="/wiki/Pulmonary_wedge_pressure" title="Pulmonary wedge pressure">pulmonary artery wedge pressure</a> (also called pulmonary artery occlusion pressure or PAOP) is a measurement in which one of the pulmonary arteries is occluded, and the pressure downstream from the occlusion is measured in order to approximate the left atrial pressure.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Therefore, the numerator of the above equation is the pressure difference between the input to the pulmonary blood circuit (where the heart's right ventricle connects to the pulmonary trunk) and the output of the circuit (which is the input to the left atrium of the heart). </p> <div class="mw-heading mw-heading2"><h2 id="Regulation">Regulation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=6" title="Edit section: Regulation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>There are many factors that influence vascular resistance. <a href="/wiki/Compliance_(physiology)#Blood_vessels" title="Compliance (physiology)">Vascular compliance</a> is determined by the <a href="/wiki/Muscle_tone" title="Muscle tone">muscle tone</a> in the <a href="/wiki/Smooth_muscle_tissue" class="mw-redirect" title="Smooth muscle tissue">smooth muscle tissue</a> of the <a href="/wiki/Tunica_media" title="Tunica media">tunica media</a> and the <a href="/wiki/Elasticity_(physics)" title="Elasticity (physics)">elasticity</a> of the <a href="/wiki/Elastic_fiber" title="Elastic fiber">elastic fibers</a> there, but the muscle tone is subject to continual <a href="/wiki/Homeostasis" title="Homeostasis">homeostatic</a> changes by <a href="/wiki/Hormone" title="Hormone">hormones</a> and <a href="/wiki/Cell_signaling" title="Cell signaling">cell signaling</a> molecules that induce <a href="/wiki/Vasodilation" title="Vasodilation">vasodilation</a> and <a href="/wiki/Vasoconstriction" title="Vasoconstriction">vasoconstriction</a> to keep <a href="/wiki/Blood_pressure" title="Blood pressure">blood pressure</a> and <a href="/wiki/Blood_flow" class="mw-redirect" title="Blood flow">blood flow</a> within <a href="/wiki/Reference_range" title="Reference range">reference ranges</a>.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p>In a first approach, based on fluids dynamics (where the flowing material is continuous and made of continuous atomic or molecular bonds, the internal friction happen between continuous parallel layers of different velocities) factors that influence vascular resistance are represented in an adapted form of the <a href="/wiki/Hagen%E2%80%93Poiseuille_equation" title="Hagen–Poiseuille equation">Hagen–Poiseuille equation</a>:<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup><br /> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R={\frac {8L\eta }{\pi r^{4}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>R</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>8</mn> <mi>L</mi> <mi>η</mi> </mrow> <mrow> <mi>π</mi> <msup> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> </msup> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle R={\frac {8L\eta }{\pi r^{4}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/45034eee7c299e8862cc642072a3d885bd58f85c" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.171ex; width:9.613ex; height:5.676ex;" alt="{\displaystyle R={\frac {8L\eta }{\pi r^{4}}}}"></span></dd></dl> <p>where </p> <ul><li>R = resistance to blood flow</li> <li>L = length of the vessel</li> <li>η = <a href="/wiki/Viscosity" title="Viscosity">viscosity</a> of blood</li> <li>r = radius of the blood vessel</li></ul> <p>Vessel length is generally not subject to change in the body. </p><p>In <a href="/wiki/Hagen%E2%80%93Poiseuille_equation" title="Hagen–Poiseuille equation">Hagen–Poiseuille equation</a>, the flow layers start from the wall and, by viscosity, reach each other in the central line of the vessel following a parabolic velocity profile.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p>In a second approach, more realistic and coming from experimental observations on blood flows, according to Thurston,<sup id="cite_ref-ReferenceA_7-0" class="reference"><a href="#cite_note-ReferenceA-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> there is a plasma release-cell layering at the walls surrounding a plugged flow. It is a fluid layer in which at a distance δ, viscosity η is a function of δ written as η(δ), and these surrounding layers do not meet at the vessel centre in real blood flow. Instead, there is the plugged flow which is hyperviscous because holding high concentration of RBCs. Thurston assembled this layer to the flow resistance to describe blood flow by means of a viscosity η(δ) and thickness δ from the wall layer.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p>The blood resistance law appears as R adapted to blood flow profile : </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R={\frac {cL\eta (\delta )}{\pi \delta r^{3}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>R</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mi>c</mi> <mi>L</mi> <mi>η</mi> <mo stretchy="false">(</mo> <mi>δ</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>π</mi> <mi>δ</mi> <msup> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> </msup> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle R={\frac {cL\eta (\delta )}{\pi \delta r^{3}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7d3b26805e1d5c1e16d64bb26d5899e47d57715a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.171ex; width:12.316ex; height:6.009ex;" alt="{\displaystyle R={\frac {cL\eta (\delta )}{\pi \delta r^{3}}}}"></span> <sup id="cite_ref-ReferenceA_7-1" class="reference"><a href="#cite_note-ReferenceA-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup></dd></dl> <p>where </p> <ul><li>R = resistance to blood flow</li> <li>c = constant coefficient of flow</li> <li>L = length of the vessel</li> <li>η(δ) = <a href="/wiki/Viscosity" title="Viscosity">viscosity</a> of blood in the wall plasma release-cell layering</li> <li>r = radius of the blood vessel</li> <li>δ = distance in the plasma release-cell layer</li></ul> <p>Blood resistance varies depending on blood viscosity and its plugged flow (or sheath flow since they are complementary across the vessel section) size as well, and on the size of the vessels. </p><p>Blood viscosity increases as blood is more hemoconcentrated, and decreases as blood is more dilute. The greater the viscosity of blood, the larger the resistance will be. In the body, blood viscosity increases as red blood cell concentration increases, thus more hemodilute blood will flow more readily, while more hemoconcentrated blood will flow more slowly.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p>Counteracting this effect, decreased viscosity in a liquid results in the potential for increased turbulence. Turbulence can be viewed from outside of the closed vascular system as increased resistance, thereby countering the ease of flow of more hemodilute blood. Turbulence, particularly in large vessels, may account for some pressure change across the vascular bed. </p><p>The major regulator of vascular resistance in the body is regulation of vessel radius. In humans, there is very little pressure change as blood flows from the aorta to the large arteries, but the small arteries and arterioles are the site of about 70% of the pressure drop, and are the main regulators of SVR. When environmental changes occur (e.g. exercise, immersion in water), neuronal and hormonal signals, including binding of <a href="/wiki/Norepinephrine" title="Norepinephrine">norepinephrine</a> and <a href="/wiki/Epinephrine" class="mw-redirect" title="Epinephrine">epinephrine</a> to the α1 receptor on vascular smooth muscles, cause either <a href="/wiki/Vasoconstriction" title="Vasoconstriction">vasoconstriction</a> or <a href="/wiki/Vasodilation" title="Vasodilation">vasodilation</a>. Because resistance is inversely proportional to the fourth power of vessel radius, changes to arteriole diameter can result in large increases or decreases in vascular resistance.<sup id="cite_ref-biosbcc_8-0" class="reference"><a href="#cite_note-biosbcc-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>If the resistance is inversely proportional to the fourth power of vessel radius, the resulting force exerted on the wall vessels, the parietal <a href="/wiki/Drag_(physics)" title="Drag (physics)">drag</a> force, is inversely proportional to the second power of the radius. The force exerted by the blood flow on the vessel walls is, according to the <a href="/wiki/Poiseuille_equation" class="mw-redirect" title="Poiseuille equation">Poiseuille equation</a>, the wall <a href="/wiki/Shear_stress" title="Shear stress">shear stress</a>. This wall shear stress is proportional to the pressure drop. The pressure drop is applied on the section surface of the vessel, and the wall shear stress is applied on the sides of the vessel. So the total force on the wall is proportional to the pressure drop and the second power of the radius. Thus the force exerted on the wall vessels is inversely proportional to the second power of the radius. </p><p>The blood flow resistance in a vessel is mainly regulated by the vessel radius and viscosity when blood viscosity too varies with the vessel radius. According to very recent results showing the sheath flow surrounding the <a href="/wiki/Plug_flow" title="Plug flow">plug flow</a> in a vessel,<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> the sheath flow size is not neglectible in the real blood flow velocity profile in a vessel. The velocity profile is directly linked to flow resistance in a vessel. The viscosity variations, according to Thurston,<sup id="cite_ref-ReferenceA_7-2" class="reference"><a href="#cite_note-ReferenceA-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> are also balanced by the sheath flow size around the plug flow. The secondary regulators of vascular resistance, after vessel radius, is the sheath flow size and its viscosity. </p><p>Thurston,<sup id="cite_ref-ReferenceA_7-3" class="reference"><a href="#cite_note-ReferenceA-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> as well, shows that the resistance R is constant, where, for a defined vessel radius, the value η(δ)/δ is constant in the sheath flow. </p><p>Vascular resistance depends on blood flow which is divided into 2 adjacent parts : a plug flow, highly concentrated in RBCs, and a sheath flow, more fluid plasma release-cell layering. Both coexist and have different viscosities, sizes and velocity profiles in the vascular system.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p>Combining Thurston's work with the <a href="/wiki/Hagen-Poiseuille_equation" class="mw-redirect" title="Hagen-Poiseuille equation">Hagen-Poiseuille equation</a> shows that blood flow exerts a force on vessel walls which is inversely proportional to the radius and the sheath flow thickness. It is proportional to the mass flow rate and blood viscosity. </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F={\frac {QcL\eta (\delta )}{\pi \delta r}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>F</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mi>Q</mi> <mi>c</mi> <mi>L</mi> <mi>η</mi> <mo stretchy="false">(</mo> <mi>δ</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mi>π</mi> <mi>δ</mi> <mi>r</mi> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F={\frac {QcL\eta (\delta )}{\pi \delta r}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c01eb86567d40834b6cd1761db8d8b4d131d21c7" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:14.131ex; height:5.843ex;" alt="{\displaystyle F={\frac {QcL\eta (\delta )}{\pi \delta r}}}"></span> <sup id="cite_ref-ReferenceA_7-4" class="reference"><a href="#cite_note-ReferenceA-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup></dd></dl> <p>where </p> <ul><li>F = Force exerted by blood flow on vessel walls</li> <li>Q = Volumetric flow rate</li> <li>c = constant coefficient of flow</li> <li>L = length of the vessel</li> <li>η(δ) = dynamic <a href="/wiki/Viscosity" title="Viscosity">viscosity</a> of blood in the wall plasma release-cell layering</li> <li>r = radius of the blood vessel</li> <li>δ = distance in the plasma release-cell layer or sheath flow thickness</li></ul> <div class="mw-heading mw-heading3"><h3 id="Other_factors">Other factors</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=7" title="Edit section: Other factors"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Many of the <a href="/wiki/Platelet" title="Platelet">platelet</a>-derived substances, including <a href="/wiki/Serotonin" title="Serotonin">serotonin</a>, are vasodilatory when the <a href="/wiki/Endothelium" title="Endothelium">endothelium</a> is intact and are vasoconstrictive when the endothelium is damaged.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p><b>Cholinergic stimulation</b> causes release of <a href="/wiki/Endothelium-derived_relaxing_factor" title="Endothelium-derived relaxing factor">endothelium-derived relaxing factor</a> (EDRF) (later it was discovered that EDRF was <a href="/wiki/Nitric_oxide" title="Nitric oxide">nitric oxide</a>) from intact endothelium, causing vasodilation. If the endothelium is damaged, cholinergic stimulation causes vasoconstriction.<sup id="cite_ref-Satoskar_10-0" class="reference"><a href="#cite_note-Satoskar-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Adenosine" title="Adenosine">Adenosine</a> most likely does not play a role in maintaining the vascular resistance in the resting state. However, it causes vasodilation and decreased vascular resistance during hypoxia. Adenosine is formed in the myocardial cells during hypoxia, ischemia, or vigorous work, due to the breakdown of high-energy phosphate compounds (e.g., <a href="/wiki/Adenosine_monophosphate" title="Adenosine monophosphate">adenosine monophosphate</a>, AMP). Most of the adenosine that is produced leaves the cell and acts as a direct vasodilator on the vascular wall. Because adenosine acts as a direct vasodilator, it is not dependent on an intact endothelium to cause vasodilation.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p>Adenosine causes vasodilation in the small and medium-sized resistance arterioles (less than 100 μm in diameter). When adenosine is administered it can cause a <a href="/wiki/Coronary_steal" title="Coronary steal">coronary steal</a> phenomenon,<sup id="cite_ref-pmid12934764_11-0" class="reference"><a href="#cite_note-pmid12934764-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> where the vessels in healthy tissue dilate more than diseased vessels. When this happens blood is shunted from potentially <a href="/wiki/Ischemia" title="Ischemia">ischemic</a> tissue that can now become <a href="/wiki/Ischemia" title="Ischemia">ischemic</a> tissue. This is the principle behind adenosine <a href="/wiki/Cardiac_stress_test" title="Cardiac stress test">stress testing</a>. Adenosine is quickly broken down by <a href="/wiki/Adenosine_deaminase" title="Adenosine deaminase">adenosine deaminase</a>, which is present in <a href="/wiki/Red_blood_cell" title="Red blood cell">red cells</a> and the vessel wall.<sup id="cite_ref-Opie_12-0" class="reference"><a href="#cite_note-Opie-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> The <a href="/wiki/Coronary_steal" title="Coronary steal">coronary steal</a> and the <a href="/wiki/Cardiac_stress_test" title="Cardiac stress test">stress test</a> can be quickly terminated by stopping the adenosine infusion. </p> <div class="mw-heading mw-heading2"><h2 id="Systemic">Systemic</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=8" title="Edit section: Systemic"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A decrease in SVR (e.g., during exercising) will result in an increased flow to tissues and an increased venous flow back to the heart. An increased SVR, as occurs with some medications, will decrease flow to tissues and decrease venous flow back to the heart. <a href="/wiki/Vasoconstriction" title="Vasoconstriction">Vasoconstriction</a> and an increased SVR is particularly true of drugs the stimulate alpha(1) adrenergic receptors.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Pulmonary">Pulmonary</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=9" title="Edit section: Pulmonary"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The major determinant of vascular resistance is <i>small arteriolar</i> (known as resistance <a href="/wiki/Arteriole" title="Arteriole">arterioles</a>) tone. These vessels are from 450 <a href="/wiki/Micrometre" title="Micrometre">μm</a> down to 100 μm in diameter (as a comparison, the diameter of a <a href="/wiki/Capillary" title="Capillary">capillary</a> is about 5 to 10 μm). Another determinant of vascular resistance is the <i>pre-capillary <a href="/wiki/Arterioles" class="mw-redirect" title="Arterioles">arterioles</a></i>. These arterioles are less than 100 μm in diameter. They are sometimes known as autoregulatory vessels since they can dynamically change in diameter to increase or reduce blood flow.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p>Any change in the <a href="/wiki/Viscosity" title="Viscosity">viscosity</a> of blood (such as due to a change in <a href="/wiki/Hematocrit" title="Hematocrit">hematocrit</a>) would also affect the measured vascular resistance.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p>Pulmonary vascular resistance (PVR) also depends on the lung volume, and PVR is lowest at the <a href="/wiki/Functional_residual_capacity" title="Functional residual capacity">functional residual capacity</a> (FRC). The highly compliant nature of the pulmonary circulation means that the degree of lung distention has a large effect on PVR. This results primarily due to effects on the alveolar and extra-alveolar vessels. During inspiration, increased lung volumes cause alveolar expansion and lengthwise stretching of the interstitial alveolar vessels. This increases their length and reduces their diameter, thus increasing alveolar vessel resistance. On the other hand, decreased lung volumes during expiration cause the extra-alveolar arteries and veins to become narrower due to decreased radial traction from adjacent tissues. This leads to an increase in extra-alveolar vessel resistance. PVR is calculated as a sum of the alveolar and extra-alveolar resistances as these vessels lie in series with each other. Because the alveolar and extra-alveolar resistances are increased at high and low lung volumes respectively, the total PVR takes the shape of a U curve. The point at which PVR is the lowest is near the FRC.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading2"><h2 id="Coronary">Coronary</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=10" title="Edit section: Coronary"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The regulation of tone in the coronary arteries is a complex subject. There are a number of mechanisms for regulating coronary vascular tone, including metabolic demands (i.e. hypoxia), neurologic control, and endothelial factors (i.e. <a href="/wiki/EDRF" class="mw-redirect" title="EDRF">EDRF</a>, <a href="/wiki/Endothelin" title="Endothelin">endothelin</a>).<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p><p>Local metabolic control (based on metabolic demand) is the most important mechanism of control of coronary flow. Decreased tissue oxygen content and increased tissue CO<sub>2</sub> content act as vasodilators. Acidosis acts as a direct coronary vasodilator and also potentiates the actions of <a href="/wiki/Adenosine" title="Adenosine">adenosine</a> on the coronary vasculature.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2021)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=11" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Arterial_resistivity_index" title="Arterial resistivity index">Arterial resistivity index</a></li> <li><a href="/wiki/Hemodynamics" title="Hemodynamics">Hemodynamics</a></li> <li><a href="/wiki/Blood_pressure" title="Blood pressure">Blood pressure</a></li> <li><a href="/wiki/Adenosine" title="Adenosine">Adenosine</a></li> <li><a href="/wiki/Perfusion" title="Perfusion">Perfusion</a></li> <li><a href="/wiki/Cardiac_output" title="Cardiac output">Cardiac output</a></li> <li><a href="/wiki/Vasoconstriction" title="Vasoconstriction">Vasoconstriction</a></li> <li><a href="/wiki/Vasodilation" title="Vasodilation">Vasodilation</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=12" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-Fuster2004-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-Fuster2004_1-0">^</a></b></span> <span class="reference-text">Fuster, V.; Alexander, R.W.; O'Rourke, R.A. (2004) <i>Hurst's the heart, book 1</i>. 11th Edition, McGraw-Hill Professional, Medical Pub. Division. Page 513. <style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-07-143224-5" title="Special:BookSources/978-0-07-143224-5">978-0-07-143224-5</a>.</span> </li> <li id="cite_note-WashingtonSurgery2008-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-WashingtonSurgery2008_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-WashingtonSurgery2008_2-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Table 30-1 in: <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTrudie_A_Goers;_Washington_University_School_of_Medicine_Department_of_Surgery;_Klingensmith,_Mary_E;_Li_Ern_Chen;_Sean_C_Glasgow2008" class="citation book cs1">Trudie A Goers; <a href="/wiki/Washington_University_School_of_Medicine" title="Washington University School of Medicine">Washington University School of Medicine</a> Department of Surgery; Klingensmith, Mary E; Li Ern Chen; Sean C Glasgow (2008). <i>The Washington manual of surgery</i>. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7817-7447-5" title="Special:BookSources/978-0-7817-7447-5"><bdi>978-0-7817-7447-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Washington+manual+of+surgery&rft.place=Philadelphia&rft.pub=Wolters+Kluwer+Health%2FLippincott+Williams+%26+Wilkins&rft.date=2008&rft.isbn=978-0-7817-7447-5&rft.au=Trudie+A+Goers%3B+Washington+University+School+of+Medicine+Department+of+Surgery%3B+Klingensmith%2C+Mary+E%3B+Li+Ern+Chen%3B+Sean+C+Glasgow&rfr_id=info%3Asid%2Fen.wikipedia.org%3AVascular+resistance" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_book" title="Template:Cite book">cite book</a>}}</code>: CS1 maint: multiple names: authors list (<a href="/wiki/Category:CS1_maint:_multiple_names:_authors_list" title="Category:CS1 maint: multiple names: authors list">link</a>)</span></span> </li> <li id="cite_note-dyn-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-dyn_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-dyn_3-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-dyn_3-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-dyn_3-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text">Derived from values in dyn·s/cm<sup>5</sup></span> </li> <li id="cite_note-:0-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-:0_4-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLevickLevick1991" class="citation book cs1">Levick, J. Rodney; Levick, J. R. (1991). <i>An introduction to cardiovascular physiology</i>. London Boston: Butterworths. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7506-1028-5" title="Special:BookSources/978-0-7506-1028-5"><bdi>978-0-7506-1028-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=An+introduction+to+cardiovascular+physiology&rft.place=London+Boston&rft.pub=Butterworths&rft.date=1991&rft.isbn=978-0-7506-1028-5&rft.aulast=Levick&rft.aufirst=J.+Rodney&rft.au=Levick%2C+J.+R.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AVascular+resistance" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLevick1991" class="citation book cs1">Levick, J. R. (1991). <i>An introduction to cardiovascular physiology</i>. London; Boston: Butterworths. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7506-1028-5" title="Special:BookSources/978-0-7506-1028-5"><bdi>978-0-7506-1028-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=An+introduction+to+cardiovascular+physiology&rft.place=London%3B+Boston&rft.pub=Butterworths&rft.date=1991&rft.isbn=978-0-7506-1028-5&rft.aulast=Levick&rft.aufirst=J.+R.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AVascular+resistance" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text">University of Virginia Health System.<a rel="nofollow" class="external text" href="http://www.healthsystem.virginia.edu/internet/anesthesiology-elective/cardiac/pacphys.cfm">"The Physiology: Pulmonary Artery Catheters"</a></span> </li> <li id="cite_note-ReferenceA-7"><span class="mw-cite-backlink">^ <a href="#cite_ref-ReferenceA_7-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-ReferenceA_7-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-ReferenceA_7-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-ReferenceA_7-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-ReferenceA_7-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text">GB Thurston, Viscosity and viscoelasticity of blood in small diameter tubes, Microvasular Research 11, 133 146, 1976</span> </li> <li id="cite_note-biosbcc-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-biosbcc_8-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.biosbcc.net/doohan/sample/htm/COandMAPhtm.htm">"Cardiac Output and Blood Pressure"</a>. biosbcc<span class="reference-accessdate">. Retrieved <span class="nowrap">7 April</span> 2011</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Cardiac+Output+and+Blood+Pressure&rft.pub=biosbcc&rft_id=http%3A%2F%2Fwww.biosbcc.net%2Fdoohan%2Fsample%2Fhtm%2FCOandMAPhtm.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AVascular+resistance" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text">Measurement of real pulsatile blood flow using X-ray PIV technique with CO<sub>2</sub> microbubbles, Hanwook Park, Eunseop Yeom, Seung-Jun Seo, Jae-Hong Lim & Sang-Joon Lee, NATURE, <i>Scientific Reports</i> <b>5</b>, Article number: 8840 (2015), <abbr>doi</abbr>:10.1038/srep08840.</span> </li> <li id="cite_note-Satoskar-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-Satoskar_10-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSatoskarBhandarkar2020" class="citation book cs1">Satoskar, RS; Bhandarkar, SD (2020). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=FR4OEAAAQBAJ&pg=PA268"><i>Pharmacology and Pharmacotherapeutics</i></a>. Elsevier Health Sciences. p. 268. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-8131257067" title="Special:BookSources/978-8131257067"><bdi>978-8131257067</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Pharmacology+and+Pharmacotherapeutics&rft.pages=268&rft.pub=Elsevier+Health+Sciences&rft.date=2020&rft.isbn=978-8131257067&rft.aulast=Satoskar&rft.aufirst=RS&rft.au=Bhandarkar%2C+SD&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DFR4OEAAAQBAJ%26pg%3DPA268&rfr_id=info%3Asid%2Fen.wikipedia.org%3AVascular+resistance" class="Z3988"></span></span> </li> <li id="cite_note-pmid12934764-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-pmid12934764_11-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMasugataPetersLafitte2003" class="citation journal cs1">Masugata H, Peters B, Lafitte S, et al. (2003). "Assessment of adenosine-induced coronary steal in the setting of coronary occlusion based on the extent of opacification defects by myocardial contrast echocardiography". <i>Angiology</i>. <b>54</b> (4): 443–8. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1177%2F000331970305400408">10.1177/000331970305400408</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/12934764">12934764</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:42646704">42646704</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Angiology&rft.atitle=Assessment+of+adenosine-induced+coronary+steal+in+the+setting+of+coronary+occlusion+based+on+the+extent+of+opacification+defects+by+myocardial+contrast+echocardiography&rft.volume=54&rft.issue=4&rft.pages=443-8&rft.date=2003&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A42646704%23id-name%3DS2CID&rft_id=info%3Apmid%2F12934764&rft_id=info%3Adoi%2F10.1177%2F000331970305400408&rft.aulast=Masugata&rft.aufirst=H&rft.au=Peters%2C+B&rft.au=Lafitte%2C+S&rfr_id=info%3Asid%2Fen.wikipedia.org%3AVascular+resistance" class="Z3988"></span></span> </li> <li id="cite_note-Opie-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-Opie_12-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFOpie2004" class="citation book cs1"><a href="/wiki/Lionel_Opie" title="Lionel Opie">Opie, Lionel H.</a> (2004). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=CPVSg69CPMsC&pg=PA286"><i>Heart Physiology: From Cell to Circulation</i></a>. Lippincott Williams & Wilkins. p. 286. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0781742781" title="Special:BookSources/0781742781"><bdi>0781742781</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Heart+Physiology%3A+From+Cell+to+Circulation&rft.pages=286&rft.pub=Lippincott+Williams+%26+Wilkins&rft.date=2004&rft.isbn=0781742781&rft.aulast=Opie&rft.aufirst=Lionel+H.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DCPVSg69CPMsC%26pg%3DPA286&rfr_id=info%3Asid%2Fen.wikipedia.org%3AVascular+resistance" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFThieleNemergutLynch2011" class="citation journal cs1">Thiele, Robert H.; Nemergut, Edward C.; Lynch, Carl (2011-08-01). <a rel="nofollow" class="external text" href="https://doi.org/10.1213%2FANE.0b013e3182124c0e">"The physiologic implications of isolated alpha(1) adrenergic stimulation"</a>. <i>Anesthesia and Analgesia</i>. <b>113</b> (2): 284–296. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1213%2FANE.0b013e3182124c0e">10.1213/ANE.0b013e3182124c0e</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1526-7598">1526-7598</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/21519050">21519050</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Anesthesia+and+Analgesia&rft.atitle=The+physiologic+implications+of+isolated+alpha%281%29+adrenergic+stimulation&rft.volume=113&rft.issue=2&rft.pages=284-296&rft.date=2011-08-01&rft.issn=1526-7598&rft_id=info%3Apmid%2F21519050&rft_id=info%3Adoi%2F10.1213%2FANE.0b013e3182124c0e&rft.aulast=Thiele&rft.aufirst=Robert+H.&rft.au=Nemergut%2C+Edward+C.&rft.au=Lynch%2C+Carl&rft_id=https%3A%2F%2Fdoi.org%2F10.1213%252FANE.0b013e3182124c0e&rfr_id=info%3Asid%2Fen.wikipedia.org%3AVascular+resistance" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text">Robert F. Brooker, John F. IV Butterworth, Dalane W. Kitzman, Jeffrey M. Berman, Hillel I. Kashtan, A. Colin McKinley; Treatment of Hypotension after Hyperbaric Tetracaine Spinal Anesthesia : A Randomized, Double-blind, Cross-over Comparison of Phenylephrine and Epinephrine. Anesthesiology 1997; 86:797–805 <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1097%2F00000542-199704000-00009">10.1097/00000542-199704000-00009</a></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=13" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Grossman W, Baim D. <i>Grossman's</i> <i>Cardiac Catheterization, Angiography, and Intervention</i>, Sixth Edition. Page 172, Tabe 8.1 <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-683-30741-X" title="Special:BookSources/0-683-30741-X">0-683-30741-X</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Vascular_resistance&action=edit&section=14" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://booktine.com/systemic-vascularresistance">Heart information: Systemic vascular resistance</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist 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class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Cardiac_output" title="Cardiac output">Cardiac output</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cardiac_cycle" title="Cardiac cycle">Cardiac cycle</a></li> <li><a href="/wiki/Cardiac_output" title="Cardiac output">Cardiac output</a> <ul><li><a href="/wiki/Heart_rate" title="Heart rate">Heart rate</a></li> <li><a href="/wiki/Stroke_volume" title="Stroke volume">Stroke volume</a></li></ul></li> <li><a href="/wiki/Stroke_volume" title="Stroke volume">Stroke volume</a> <ul><li><a href="/wiki/End-diastolic_volume" title="End-diastolic volume">End-diastolic volume</a></li> <li><a href="/wiki/End-systolic_volume" title="End-systolic volume">End-systolic volume</a></li></ul></li> <li><a href="/wiki/Afterload" title="Afterload">Afterload</a></li> <li><a href="/wiki/Preload_(cardiology)" title="Preload (cardiology)">Preload</a></li> <li><a href="/wiki/Frank%E2%80%93Starling_law" title="Frank–Starling law">Frank–Starling law</a></li> <li><a href="/wiki/Cardiac_function_curve" title="Cardiac function curve">Cardiac function curve</a></li> <li><a href="/wiki/Venous_return_curve" class="mw-redirect" title="Venous return curve">Venous return curve</a></li> <li><a href="/wiki/Wiggers_diagram" title="Wiggers diagram">Wiggers diagram</a></li> <li><a href="/wiki/Pressure_volume_diagram" class="mw-redirect" title="Pressure volume diagram">Pressure volume diagram</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Echocardiography" title="Echocardiography">Ultrasound</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ventricle_(heart)#Dimensions" title="Ventricle (heart)">Fractional shortening</a> = (<a href="/wiki/End-diastolic_dimension" class="mw-redirect" title="End-diastolic dimension">End-diastolic dimension</a></li> <li><a href="/wiki/End-systolic_dimension" class="mw-redirect" title="End-systolic dimension">End-systolic dimension</a>) / End-diastolic dimension</li> <li><a href="/wiki/Aortic_valve_area_calculation" title="Aortic valve area calculation">Aortic valve area calculation</a></li> <li><a href="/wiki/Ejection_fraction" title="Ejection fraction">Ejection fraction</a></li> <li><a href="/wiki/Cardiac_index" title="Cardiac index">Cardiac index</a></li> <li><a href="/wiki/Left_atrial_volume" title="Left atrial volume">Left atrial volume</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Heart_rate" title="Heart rate">Heart rate</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cardiac_pacemaker" title="Cardiac pacemaker">Cardiac pacemaker</a></li> <li><a href="/wiki/Chronotropic" title="Chronotropic">Chronotropic</a> (<a href="/wiki/Heart_rate" title="Heart rate">Heart rate</a>)</li> <li><a href="/wiki/Dromotropic" title="Dromotropic">Dromotropic</a> (<a href="/wiki/Nerve_conduction_velocity" title="Nerve conduction velocity">Conduction velocity</a>)</li> <li><a href="/wiki/Inotrope" title="Inotrope">Inotropic</a> (Contractility)</li> <li><a href="/wiki/Bathmotropic" title="Bathmotropic">Bathmotropic</a> (Excitability)</li> <li><a href="/wiki/Lusitropy" title="Lusitropy">Lusitropic</a> (Relaxation)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Conduction</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Electrical_conduction_system_of_the_heart" class="mw-redirect" title="Electrical conduction system of the heart">Conduction system</a></li> <li><a href="/wiki/Cardiac_electrophysiology" title="Cardiac electrophysiology">Cardiac electrophysiology</a></li> <li>Action potential <ul><li><a href="/wiki/Cardiac_action_potential" title="Cardiac action potential">cardiac </a></li> <li><a href="/wiki/Atrial_action_potential" title="Atrial action potential">atrial</a></li> <li><a href="/wiki/Ventricular_action_potential" title="Ventricular action potential">ventricular</a></li></ul></li> <li><a href="/wiki/Effective_refractory_period" title="Effective refractory period">Effective refractory period</a></li> <li><a href="/wiki/Pacemaker_potential" title="Pacemaker potential">Pacemaker potential</a></li> <li><a href="/wiki/Electrocardiography" title="Electrocardiography">Electrocardiography</a> <ul><li><a href="/wiki/P_wave_(electrocardiography)" title="P wave (electrocardiography)">P wave</a></li> <li><a href="/wiki/PR_interval" title="PR interval">PR interval</a></li> <li><a href="/wiki/QRS_complex" title="QRS complex">QRS complex</a></li> <li><a href="/wiki/QT_interval" title="QT interval">QT interval</a></li> <li><a href="/wiki/ST_segment" title="ST segment">ST segment</a></li> <li><a href="/wiki/T_wave" title="T wave">T wave</a></li> <li><a href="/wiki/U_wave" title="U wave">U wave</a></li></ul></li> <li><a href="/wiki/Hexaxial_reference_system" title="Hexaxial reference system">Hexaxial reference system</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Chamber pressure</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Central_venous_pressure" title="Central venous pressure">Central venous</a></li> <li>Right <ul><li><a href="/wiki/Right_atrial_pressure" title="Right atrial pressure">atrial</a></li> <li><a href="/wiki/Right_ventricular_pressure" class="mw-redirect" title="Right ventricular pressure">ventricular</a></li></ul></li> <li><a href="/wiki/Pulmonary_artery_pressure" class="mw-redirect" title="Pulmonary artery pressure">pulmonary artery</a> <ul><li><a href="/wiki/Pulmonary_wedge_pressure" title="Pulmonary wedge pressure">wedge</a></li></ul></li> <li>Left <ul><li><a href="/wiki/Pulmonary_wedge_pressure" title="Pulmonary wedge pressure">atrial</a></li> <li><a href="/wiki/Left_ventricular_pressure" class="mw-redirect" title="Left ventricular pressure">ventricular</a></li></ul></li> <li><a href="/wiki/Aortic_pressure" title="Aortic pressure">Aortic</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ventricular_remodeling" title="Ventricular remodeling">Ventricular remodeling</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Circulatory_system" title="Circulatory system">Vascular system</a>/<br /><a href="/wiki/Hemodynamics" title="Hemodynamics">hemodynamics</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Hemodynamics" title="Hemodynamics">Blood flow</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Compliance_(physiology)" title="Compliance (physiology)">Compliance</a></li> <li><a class="mw-selflink selflink">Vascular resistance</a></li> <li><a href="/wiki/Pulse" title="Pulse">Pulse</a></li> <li><a href="/wiki/Perfusion" title="Perfusion">Perfusion</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Blood_pressure" title="Blood pressure">Blood pressure</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pulse_pressure" title="Pulse pressure">Pulse pressure</a> <ul><li><a href="/wiki/Systole" title="Systole">Systolic</a></li> <li><a href="/wiki/Diastole" title="Diastole">Diastolic</a></li></ul></li> <li><a href="/wiki/Mean_arterial_pressure" title="Mean arterial pressure">Mean arterial pressure</a></li> <li><a href="/wiki/Jugular_venous_pressure" title="Jugular venous pressure">Jugular venous pressure</a></li> <li><a href="/wiki/Portal_venous_pressure" title="Portal venous pressure">Portal venous pressure</a></li> <li><a href="/wiki/Critical_closing_pressure" title="Critical closing pressure">Critical closing pressure</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Cardiovascular_physiology#Regulation_of_blood_pressure" title="Cardiovascular physiology">Regulation of BP</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Baroreflex" title="Baroreflex">Baroreflex</a></li> <li><a href="/wiki/Kinin%E2%80%93kallikrein_system" title="Kinin–kallikrein system">Kinin–kallikrein system</a></li> <li><a href="/wiki/Renin%E2%80%93angiotensin_system" title="Renin–angiotensin system">Renin–angiotensin system</a></li> <li><a href="/wiki/Vasoconstriction" title="Vasoconstriction">Vasoconstrictors</a></li> <li><a href="/wiki/Vasodilation" title="Vasodilation">Vasodilators</a></li> <li><a href="/wiki/Autoregulation" title="Autoregulation">Autoregulation</a> <ul><li><a href="/wiki/Myogenic_mechanism" title="Myogenic mechanism">Myogenic mechanism</a></li> <li><a href="/wiki/Tubuloglomerular_feedback" title="Tubuloglomerular feedback">Tubuloglomerular feedback</a></li> <li><a href="/wiki/Cerebral_autoregulation" title="Cerebral autoregulation">Cerebral autoregulation</a></li></ul></li> <li><a href="/wiki/Paraganglion" title="Paraganglion">Paraganglia</a> <ul><li><a href="/wiki/Aortic_body" title="Aortic body">Aortic body</a></li> <li><a href="/wiki/Carotid_body" title="Carotid body">Carotid body</a></li> <li><a href="/wiki/Glomus_cell" title="Glomus cell">Glomus cell</a></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" 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