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83 Cards in this Set
- Front
- Back
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Pressure in the right ventricle
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25/0 mmHg
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Pressure in the pulmonary artery
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25/8 mmHg
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Mean pulmonary artery pressure
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15 mmHg
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Pulmonary capillary pressure
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7-9 mmHg
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Pulmonary venous pressure
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5 mmHg
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Left atrium pressure
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5-10 mmHg
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Left ventricle pressure
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120/0 mmHg
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Aortic pressure
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120/80 mmHg
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Mean arterial blood pressure
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(Systolic - diastolic / 3) + diastolic = 93 mmHg
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Skeletal muscle capillary pressure
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30 mmHg
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Renal glomerular capillary pressure
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45-50 mmHg
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Peripheral vein pressure
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15 mmHg
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Right atrium pressure (central venous)
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0 mmHg
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Systemic circuit Vs. pulmonary system
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Cardiac output and heart rate is the same as they're connected in series. The systemic circuit has higher resistance and lower compliance therefore work of the right ventricle is lower.
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Highest resistance segment of the systemic circulation
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Arterioles. Also responsible for greatest pressure drop.
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Largest and smallest cross-sectional areas of the systemic circuit
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Largest: capillaries; smallest: aorta
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Fastest and slowest velocities in the systemic circuit
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Velocity is inversely proportional to cross-sectional area. Aorta has fastest velocity; capillaries have slowest velocity.
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Largest blood volumes in the cardiovascular system
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Systemic veins then pulmonary system have the largest blood volume. Both represent reservoirs due to high compliance.
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Poiseuille equation
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Q = P1 - P2 / R;
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Determinants of resistance
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R ∝ vL / r4; if radius doubles, resistance decreses to 1/16; if radius decreases by half, resistance increases 16-fold
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Reynolds number
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RN = diameter x velocity x density / viscosity. If > 2,000 --> turbulent flow; if < 2,000 --> laminar flow
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Vessel with the most turbulent flow
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Aorta - has large diameter, high velocity. In anemia (↓ viscosity) --> aortic murmur
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Features of a series circuit
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Flow is the same at all points; the total resistance is the sum of all resistances; adding a resistor decreases flow at all points and vice versa;
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↓ resistance, ↑ capillary flow, ↑ capillary pressure
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Arteriole dilation - beta agonists, alpha blockers, ↓ sympathetic, metabolic dilation, ACEIs
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↑ resistance, ↓ capillary flow, ↓ capillary pressure
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Arteriole constriction - alpha agonists, beta blockers, ↑ sympathetic, angiotensin II
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↓ resistance, ↑ capillary flow, ↓ capillary pressure
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Venous dilation - ↑ metabolism
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↑ resistance, ↓ capillary flow, ↑ capillary pressure
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Venous constriction - physical compression, ↑ sympathetic
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↑ capillary flow, ↑ capillary pressure, no change in resistance
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↑ arterial pressure - ↑ CO, volume expansion
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↓ capillary flow, ↓ capillary pressure, no change in resistance
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↓ arterial pressure - ↓ CO, hemorrhage, dehydration
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↓ capillary flow, ↑ capillary pressure, no change in resistance
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↑ venous pressure - CHF, physical compression
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↑ capillary flow, ↓ capillary pressure, no change in resistance
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↓ venous pressure - hemorrhage, dehydration
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Characteristics of parallel circuits
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The reciprocal of the total resistance is the sum of the reciprocal of the individual resistances. Connecting a resistance in parallel lowers resistance, total resistance is always less than individual resistances.
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Parallel circuits with greatest resistance
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Coronary > cerebral > renal > pulmonary
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What happens if a parallel circuit is added?
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TPR decreases, pressure would decrease but a compensatory increases in CO maintains same pressure. Obesity.
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What happens if a parallel circuit is removed?
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TPR increases, blood pressure increases, CO might decrease to compensate increased blood pressure.
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Wall tension
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T ∝ Pr. In aneurysm, tension is high due to grater radius.
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Factors that increase systolic pressure
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↑ stroke volume, ↓ HR, ↓ compliance
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Factors that decrease systolic pressure
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↓ stroke volume, ↑ HR, ↑ compliance
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Factors that decrease diastolic pressure
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↓ TPR, ↓ HR, ↓ stroke volume, ↓ compliance
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Factors that increase diastolic pressure
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↑ TPR, ↑ HR, ↑ stroke volume, ↑ compliance
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Factors that increase pulse pressure
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↑ stroke volume (systolic > diastolic); ↓ compliance (systolic increases and diastolic decreases)
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Determinants of mean arterial pressure
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MAP = CO x TPR
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What happens to cardiac output and mean arterial pressure if TPR increases?
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MAP increases and CO decreases
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What happens to cardiac output and TPR if mean arterial pressure decreases?
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TPR decreases, CO decreases but then increases to compensate and maintain blood pressure
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Hemodynamic changes in hemorrhage
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Loss of circulating volume and CO --> less firing of carotid sinus (↓ BP) --> reflex sympathetic ↑ in TPR and CO --> ↓ venous compliance --> ↑ circulating volume --> compensated CO and BP
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Hemodynamic changes during exercise
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Dilation of arterioles --> ↓ TPR --> ↓ BP --> less firing of carotid sinus --> reflex sympathetic ↑ in CO --> ↑ BP
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Hemodynamic changes due to gravity
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↑ venous pressure, ↑ pooling of blood in veins, ↓ circulating blood volume (CO), ↓ BP --> compensation via carotid sinus --> ↑ TPR, ↑ HR
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Effects of inspiration on blood flow
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↓ intrapleural pressure --> ↑ venous return --> ↑ right ventricle output --> splitting of S2 --> blood in pulmonary circuit increases --> ↓ venous return to left heart --> ↓ systemic pressure --> reflex increase in HR
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Effects of expiration on blood flow
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↑ intrapleural pressure --> ↓ venous return --> ↓ pulmonary blood volume --> ↑ output of left ventricle --> ↑ systemic pressure --> reflex bradycardia
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What factor controls blood flow to capillaries?
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↑ resistance of arterioles --> ↓ capillary flow and pressure; ↓ resistance of arterioles --> ↑ capillary flow and pressure
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What factors affect capillary exchange?
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Exchange is by simple diffusion only. Proteins do not cross the capillary membrane. Factors that affect diffusion rate are: surface area, membrane thickness, concentration gradient, solubility
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When does the rate of uptake become perfusion-limited?
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When concentration of the substance reaches equilibrium between capillary and tissue. ↑ blood flow converts perfusion-limited uptake to diffusion-limited again.
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When does the rate of uptake become diffusion-limited?
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When concentration between capillary and tissue are not in equilibrium.
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What forces favor reabsorption?
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Capillary oncotic pressure and interstitial hydrostatic pressure
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What forces favor capillary filatration?
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Capillary hydrostatic pressure and interstitial oncotic pressure
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What happens to filtration in lung capillaries when intrathoracic pressure decreases?
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↓ intrathoracic pressure promotes filtration. In ARDS --> ↓ intrathoracic pressure --> pulmonary edema
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Conditions that affect capillary hydrostatic pressure
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Essential hypertension increases resistance and decreases capillary hydrostatic pressure. Hemorrhage decreases capillary hydrostatic pressure and promotes reabsorption.
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Conditions that affect capillary oncotic pressure
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Increased by dehydration. Decreased by liver and renal disease and saline infusion
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Conditions that affect interstitial oncotic pressure
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Increased by lymphatic blockage and increased capillary permeability to proteins (burns)
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Conditions that affect insterstitial hydrostatic pressure
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Increased by negative intrathoracic pressure in ARDS
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Fick principle
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Measures cardiac output. Flow = O2 consumption / O2 concentration difference across the organ
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Intrinsic autoregulation of blood flow
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Resistance of arterioles is changed in order to regulate flow. No nerves or hormones involved. Independent of BP.
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Metabolic hypothesis of autoregulation
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Tissue can produce a vasodilatory metabolite that regulates blood flow. Example adenosine in coronaries.
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Tissues that have autoregulation of blood flow
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Cerebral, coronary and exercising skeletal muscle circulations
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Extrinsic regulation of blood flow
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Controlled by nervous and hormonal influences. NE via β2 vasodilates, via α1 constricts (dose dependant). Angiotensin II constricts.
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Tissues that have extrinsic regulation of blood flow
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Resting skeletal muscle, skin
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Lowest venous PO2 in the body
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Coronary circulation due to maximal extraction of O2. To increase delivery of oxygen, flow must increase.
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Factors that control coronary circulation
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Coronary circulation occurs in diastole and its determined by stroke work of the heart. Exercise increases volume work and coronary flow. Hypertension increases pressure work and coronary flow. Vasodilation is mediated by adenosine.
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Factors that control cerebral blood flow
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Flow is proportional to arterial PCO2. Hypoventilation increases PCO2 and flow. Hyperventilation decreases PCO2 and flow. PO2 determines flow only if theres a large decrease in PO2.
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Factors that control cutaneous blood flow
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↑ sympathetic tone --> constriction of arterioles --> ↓ blood flow, ↓ blood volume in veins --> ↑ velocity (↓ cross-sectional area). Increased skin temperature --> vasodilation --> heat loss
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Highest venous PO2 in the body
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Renal circulation
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Factors that control renal circulation
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Small changes in blood pressure invoke autoregulatory responses. Sympathetic may influence blood flow in extreme conditions (hemorrhage, hypotension)
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Characteristics of pulmonary circuit
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Low pressure, high flow, low resistance, very compliant, hypoxic vasoconstriction.
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Pulmonary response to exercise
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↑ CO --> ↑ pulmonary pressure --> pulmonary vessel dilation (due to high compliance) --> large ↓ resistance --> ↓ pulmonary pressure
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Pulmonary response to hemorrhage
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↓ CO --> ↓ pulmonary pressure --> pulmonary vessel constriction --> large ↑ resistance --> less blood volume
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Fetal circulation: percent O2 saturation in umbilical vein
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80% O2 saturation
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Fetal circulation: percent O2 saturation in inferior vena cava
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26% O2 saturation. Mixes with hepatic vein blood --> step up to 67%
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Fetal circulation: percent O2 saturation from inferior vena cava into right atrium
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67% O2 saturation. Blood from inferior vena cava enters right atrium and passes through foramen ovale
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Fetal circulation: percent O2 saturation in superior vena cava
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40% O2 saturation. Mixes with blood from inferior vena cava (67%) and passes to right ventricle at 50% saturation
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Fetal circulation: percent O2 saturation in right ventricle
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Contains blood from superior vena cava mixed with IVC --> 50% saturation. Passes through pulmonary artery and 90% is shunted through the ductus arteriosus into aorta
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Fetal circulation: percent O2 saturation in ascending aorta
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Contains blood from inferior vena cava --> 67%
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Fetal circulation: percent O2 saturation in brachiocephalic trunk
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Blood from left ventricle (67%) mixes with blood from ductus arteriousus (50%) --> yields 65%
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Fetal circulation: percent O2 saturation in descending and abdominal aorta
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Blood from left ventricle (67%) mixes with blood from ductus arteriousus (50%) --> yields 60%
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