Pulmonary Blood Flow

Question 1

Overview of blood flow to the lungs

Answer 1

Same volume pumped, but decreased pressure due to lower resistance.

Question 2

Alveolar capillaries

Answer 2

Receive blood from RV.
Blood has low O2/high CO2.
Involved in exchange of O2 and CO2 between blood and air.
Appears like a sheet of capillaries.

Question 3

Extra-alveolar capillaries

Answer 3

Receive blood from LV.
High O2/low CO2.
Deliver O2 and CO2 to the tissue of the lungs.
Returns to the heart via PVs.
Contains venous admixture.

Question 4

Venous admixture

Answer 4

Result of mixing of shunted non-reoxygenated blood with reoxygenated. Reduces PaO2 of arterial blood and increases PaCO2 to a small degree.

Question 5

Pulmonary vascular resistance equation

Answer 5

PBP = CO x PVR

Question 6

Pulmonary vascular resistance is determined by (4):

Answer 6

High number of capillaries.
Number of available capillaries at a given point in time.
Sympathetic ton/vasoconstricting forces.
Lung volume.

Question 7

During exercise PVR:

Answer 7

Drops as more pulmonary capillaries open up to accomodate the increased CO.

Question 8

At low or very high lung volumes, resistance:

Answer 8

Increases a little because stretch of this tissue compresses the capillaries.

Question 9

Compare and contrast PVR w/ SR
Normal value
BP
Blood volume

Answer 9

PVR:
Low normal value
Low BP
5 L/min blood volume 
SR:
Moderate normal value
Higher BP
5 L/min

Question 10

Zones of the lungs

Answer 10

Zone 1 - apex
Zone 2 - mid lung
Zone 3 - base

Question 11

Zone 1

Answer 11

BP is reduced because it is slightly above the heart.
Alveoli are somewhat expanded.
Blood flow is less.

Question 12

Zone 2

Answer 12

BP is a little higher due to being at level of heart.
Alveoli are average size.
Blood flow is normal.

Question 13

Zone 3

Answer 13

BP is high due to being below the heart.
Alveoli are smaller.
Blood flow is greater than in other regions of the lung.

Question 14

NO modulation of pulmonary blood flow

Answer 14

Made by epithelium.
Causes smooth muscle relaxation and vasodilation.
Significant role in normal pulmonary blood flow.

Question 15

Endothelin 1 modulation of pulmonary blood flow

Answer 15

Made in lungs.
Vasoconstrictor.
A player in pathologic conditions - not under normal physiology.

Question 16

Thromboxane A2

Answer 16

Essentially the same as Endothelin 1.

Question 17

Starling forces control what?

Answer 17

How much fluid moves from capillary to the lung.

Question 18

Hydrostatic pressure in the lungs

Answer 18

Fluid pushing against tissue/capillary walls.

Exists in the capillary (Pc) and tissue (Pt).

Question 19

Pc

Answer 19

BP in the capillary that wants to push fluid into the alveoli.

Question 20

Pt

Answer 20

In the rest of the body, this pushes fluid into the capillary.

Question 21

Oncotic pressure in the lungs

Answer 21

Osmotic pressure of fluids involved.

Exists in plasma (PIc) and tissues (PIt).

Question 22

Plasma oncotic pressure

Answer 22

Tries to pull water into the capillary.

Question 23

Tissue oncotic pressure

Answer 23

Tries to pull water into the alveolus.

Question 24

Forces wanting to move water from capillary to alveolus (3)

Answer 24

Pc - hydrostatic pressure in capillary
PIt - oncotic pressure in tissues
Pt - hydrostatic pressure in tissues

Question 25

Forces wanting to move water from alveolus to capillary (1)

Answer 25

PIc - oncotic pressure in capillary

Question 26

Largest Starling Force in the lung

Answer 26

Pc

Question 27

Net result of Starling forces

Answer 27

Favors filtration of fluid into the alveoli.

This is bad for gas exchange.

Question 28

How does the body correct for net filtration into the alveoli?

Answer 28

The lymphatic system.

Question 29

Regional blood flow in the lung is determined by:

Answer 29

Gravity and amount of air in the region of the lung.

Question 30

Renin origin an function

Answer 30

Kidney.
Converts angiotensin (from liver) to angiotensin 1.

Question 31

ACE origin and function

Answer 31

Lungs.
Converts angiotensin 1 to angiotensin 2.
Activates bradykinin (another vasodilator).

Question 32

Why do people on ACE inhibitors commonly develop a cough?

Answer 32

Inhibits bradykinin which can build up in lungs and cause a cough.

Question 33

O2 modulation of pulmonary blood flow

Answer 33

A decrease in oxygen causes hypoxic vasoconstriction which increases PVR.