Pulmonary circulation I

Question 1

What does the bronchial circulation supply

Answer 1

conducting airways- trachea down to terminal bronchioles

Question 2

Where do bronchial arteries branch from

Answer 2

aorta or upper intercostal arteries- this means they are systemic arteries with systemic pressures

Question 3

Function of bronchial circulation

Answer 3

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

Question 4

Most common source of hemoptysis

Answer 4

bronchial arteries

Question 5

1. Learn the major functions of the pulmonary circulation

Answer 5

Gas exchange, water and solute balance in lung

Question 6

3 ways in which abnormal pulmonary circulation manifests

Answer 6

a) abnormal gas exchange (hypoxemia or hypercarbia)
b) abnormal increases in lung water (pulmonary edema)
c) pathologic increase in pulmonary vascular resistance (pulmonary hypertension)

Question 7

Pulmonary circulation equation

Answer 7

PPA- PLA = CO x PVR where PPA = mean pulmonary artery pressure, PLA = left atrial pressure (wedge pressure), CO = cardiac output, PVR = pulmonary vascular resistance

Question 8

Compare resistance, compliance, pressure and Cardiac Output of systemic vs pulmonary circulation

Answer 8

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

Question 9

How do you measure pulmonary artery pressure?

Answer 9

Non invasive echo (using ∆P=4 x V^2) or pulmonary artery catheterization. Echo often has errors

Question 10

What is Swan-Ganz catheter?

Answer 10

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

Question 11

2. Understand the major determinants of blood flow distribution in the lung

Answer 11

Intrinsic resistance changes: 1) high distensibility of the perfused vessels 2) recruiting previously unperfused vessels

Question 12

What pressures are important in determining pulmonary blood flow?

Answer 12

1) alveolar pressure (PA), 2) pulmonary arterial pressure (Pa), and 3) pulmonary venous pressure (Pv).

Question 13

Gravity effect on blood flow in lungs

Answer 13

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

Question 14

Zone 1 of lung

Answer 14

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

Question 15

Zone 2 of lung

Answer 15

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

Question 16

Zone 3 of lung

Answer 16

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.

Question 17

Describe how vasoconstriction and vasodilation regulates pulmonary circulation

Answer 17

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

Question 18

What is pulmonary edema

Answer 18

initial accumulation of fluid in the interstitial spaces followed by flooding into the alveolar space.

Question 19

What factors determine rate of fluid movement into lung interstitium? Equation

Answer 19

net hydrostatic out of capillary and oncotic pressures into the capillary acting along the microvascular wall.

Question 20

Starlings law

Answer 20

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

Question 21

Describe normal hydrostatic and oncotic pressures

Answer 21

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

Question 22

High vs low Kf

Answer 22

Filtration coefficient, Kf is a measure of the capillary filtration. High Kf indicates porous membrane while low Kf indicates less permeable membrane

Question 23

What two conditions lead to pulmonary edema

Answer 23

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)

Question 24

What are Kerly B lines

Answer 24

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

Question 25

Compare clinical setting, left atrial pressure and response to diuretics for cardiac vs noncardiac pulmonary edema

Answer 25

Cardiogenic: Seen in congestive heart failure, elevated left atrial pressure, diuretics help. Noncardiogenic: seen in pneumonia and ARDS, left atrial pressure not elevated, diuretics don’t help

Question 26

Time course of permeability vs hydrostatic pulmonary edema

Answer 26

Hydrostatic occurs within minutes, permeability occurs lower over 6-24 hrs after acute lung injury