Pulmonary circulation I Flashcards
What does the bronchial circulation supply
conducting airways- trachea down to terminal bronchioles
Where do bronchial arteries branch from
aorta or upper intercostal arteries- this means they are systemic arteries with systemic pressures
Function of bronchial circulation
Protects lung from infarction b/c the bronchial circulation provide collateral blood supply when there is a PE. Can grow into areas of diseased lung
Most common source of hemoptysis
bronchial arteries
- Learn the major functions of the pulmonary circulation
Gas exchange, water and solute balance in lung
3 ways in which abnormal pulmonary circulation manifests
a) abnormal gas exchange (hypoxemia or hypercarbia)
b) abnormal increases in lung water (pulmonary edema)
c) pathologic increase in pulmonary vascular resistance (pulmonary hypertension)
Pulmonary circulation equation
PPA- PLA = CO x PVR where PPA = mean pulmonary artery pressure, PLA = left atrial pressure (wedge pressure), CO = cardiac output, PVR = pulmonary vascular resistance
Compare resistance, compliance, pressure and Cardiac Output of systemic vs pulmonary circulation
systemic: high resistance, low compliance (more stiff due to more elastic fibers), high pressure, CO= 5L/min. Pulmonary: low resistance, high compliance (more stretchy due to less elastic fibers), low pressure, CO=5L/min
How do you measure pulmonary artery pressure?
Non invasive echo (using ∆P=4 x V^2) or pulmonary artery catheterization. Echo often has errors
What is Swan-Ganz catheter?
Flow directed pulm artery catheter with a balloon at the tip. Blood flow carries the catheter through the right heart and into the pulmonary artery. The pressure is measured through the tip of the catheter. The balloon is then advanced into a small branch of pulmonary artery to approximate the left atrial pressure which should also be equal to the LV end diastolic pressure
- Understand the major determinants of blood flow distribution in the lung
Intrinsic resistance changes: 1) high distensibility of the perfused vessels 2) recruiting previously unperfused vessels
What pressures are important in determining pulmonary blood flow?
1) alveolar pressure (PA), 2) pulmonary arterial pressure (Pa), and 3) pulmonary venous pressure (Pv).
Gravity effect on blood flow in lungs
While alveolar pressure is constant throughout th elung, Pulmonary artery pressure increases from the apex to the bas, so blood flow is greater at the base of the lung
Zone 1 of lung
At the apex of the lung: PA> Pa> Pv. pulmonary microvasculature is compressed because the (positive) alveolar pressure exceeds the arterial driving pressure. Blood flow in zone 1 is minimal and in healthy person this zone is very small
Zone 2 of lung
Blood flow is greater than in zone 1, but less than in zone 3. Drving pressure is difference btw arterial and alveolar pressure. Pa> PA> Pv Blood flow is greater than in zone 1, but less than in zone 3. Drving pressure is difference btw arterial and alveolar pressure. Pa> PA> Pv
Zone 3 of lung
Driving pressure is difference btw arterial and venous pressure (alveolar pressure doesn’t contribute). This is where a catheter is placed to measure pulmonary venous pressure. The most blood flow occurs here Pa> Pv> PA. Driving pressure is difference btw arterial and venous pressure (alveolar pressure doesn’t contribute). This is where a catheter is placed to measure pulmonary venous pressure. The most blood flow occurs here Pa> Pv> PA.
Describe how vasoconstriction and vasodilation regulates pulmonary circulation
Active regulation measures: 1. In hypoxic pulmonary vasoconstriction, vasoconstriction of small arteries occurs in areas with alveolar hypoxia to preserve VQ matching and direct blood flow away from hypoxic/diseased areas. Usually not necessary in healthy lungs. 2. Endogenous vasodilators/constrictors such as NO, prostacyclin, endothelin, thromboxane
What is pulmonary edema
initial accumulation of fluid in the interstitial spaces followed by flooding into the alveolar space.
What factors determine rate of fluid movement into lung interstitium? Equation
net hydrostatic out of capillary and oncotic pressures into the capillary acting along the microvascular wall.
Starlings law
Starlings law: Qf = Kf[(Pmv- Pi) - σ( ∏mv- ∏i)] where Qf = fluid filtration rate, Kf = filtration coefficient, Pmv microvascular hydrostatic pressure, Pi = interstitial space hydrostatic pressure, σ = osmotic reflection coefficient, ∏mv = microvascular oncotic pressure, ∏i = interstitial space oncotic pressure
Describe normal hydrostatic and oncotic pressures
Hydrostatic pressure is usually directed out of the capillary while oncotic pressure is usually directed into the capillary. In healthy lung, hydrostatic pressure exceeds oncotic pressure, so there is a slow flow of fluid from pasma to interstitium, which is reabsorbed by capillaries and venulesand returned to circulation by lymphatics
High vs low Kf
Filtration coefficient, Kf is a measure of the capillary filtration. High Kf indicates porous membrane while low Kf indicates less permeable membrane
What two conditions lead to pulmonary edema
Hydrostatic (Cardiogenic): Increased vascular pressure (Pmv). Increased permeability (Noncardiogenic):Proteins leave the vasculature, πmv (capillary oncotic pressure) goes down, πi (interstitial oncotic pressure) goes up, Ø effectively goes down (proteins can cross easily)
What are Kerly B lines
In hydrostatic pulmonary edema, lymphatics are engorged as they try to handle incrased fluid loads ad these are visible as small straight lines in subpleural region on CXR
