Pulmonary circulation

Question 1

How compliant are the vessels of the pulmonary circulation?

Answer 1

Highly

Question 2

What happens to blood flow in alveolar capillaries when PO2 drops? Why?

Answer 2

local vasoconstriction

To redistribute the blood to better aerated alveoli

Question 3

What are the five scenarios mentioned in class that trigger abnormal hypoxic pulmonary vasoconstriction (HPV) response?

Answer 3

Airway obstruction
Failure of ventilation
Acute lung damage
High altitude
COPD

Question 4

What triggers hypoxic pulmonary vasoconstriction?

Answer 4

Alveolar hypoxia

Question 5

How do PA, Pa, and Pv relate to each other in the upper part of the lungs?

(recall that PA = alveolar pressure, Pa = arterial pressure, and Pv = veins).

Answer 5

PA > Pa > Pv

Question 6

How do PA, Pa, and Pv relate to each other in the middle part of the lungs?

(recall that PA = alveolar pressure, Pa = arterial pressure, and Pv = veins).

Answer 6

Pa > PA > Pv

Question 7

How do PA, Pa, and Pv relate to each other in the lower part of the lungs?

(recall that PA = alveolar pressure, Pa = arterial pressure, and Pv = veins).

Answer 7

Pa > Pv > PA

Question 8

Conditions that affect blood vasculature affect what part of the lungs more, the base or the apex?

Answer 8

Base

Question 9

Blood flow is greater in the base or the apex of the lungs?

Answer 9

Base

Question 10

What happens to hydrostatic pressure in CHF? What does this cause?

Answer 10

increases

Causes increase in edema in the interstitium

Question 11

Why does ventilation have to match perfusion?

Answer 11

Need to have blood flow with oxygen

Question 12

What is the average value of V/Q?

Answer 12

0.8

Question 13

What happens to the ventilation and perfusion when going from the base to the apex of the lung?

Answer 13

Both decrease, but perfusion drops more

Question 14

What happens to the V/Q ratio when moving from the base of the lungs, to the apex? Why?

Answer 14

Increases

Q drops faster than V

Question 15

Why does TB reactivate in the upper lung zones?

Answer 15

Because there is more ventilation relative to perfusion (it is an aerobe)

Question 16

What is the V/Q ratio in the dead space?

Answer 16

infinite ventilation, no blood flow

Question 17

What is the V/Q ratio in a shunt?

Answer 17

0 (no ventilation, but tons of blood flow)

Question 18

What happens to the V/Q as you progress down the airway tree? Why?

Answer 18

more perfusion, less ventilation, thus gets smaller

Question 19

What is the physiological shunt?

Answer 19

The bronchial circulation

Question 20

If there is a communication between the left and right side of the heart, what always occurs? How?

Answer 20

Hypoxemia from RVH

Question 21

Why doesn’t hypoxemia occur with right to left shunts right away?

Answer 21

Blood flow from left to right due to pressure initially, but RVH eventually wins, and causes non oxygenated blood to shunt from the right to the left

Question 22

What happens to the V/Q ratio in PEs?

Answer 22

Infinite d/t normal ventilation, but 0 blood flow

Question 23

Which side of the heart is affected more in a PE?

Answer 23

Right d/t blockage

Question 24

What are the two major outcomes of a PE?

Answer 24

1. Right to left shunting in areas of atelectasis

2. V/Q mismatch

Question 25

What is the gold standard for PE detection?

Answer 25

V/Q (ventilation) scan

Question 26

What is a ventilation scan?

Answer 26

Looking at lung perfusion with radioactive substance

Question 27

What is the V/Q ratio in normal patients?

Answer 27

1.0, thus usually the curves will superimpose over one another

Question 28

What is the function of the bronchial arteries? What effects does this have on systemic oxygen content?

Answer 28

Supply oxygen to the lung tissues. This blood is then shunted to the left side of the heart, decreasing the overall oxygen content slightly

Question 29

What is the function of the pulmonary circulation (capacitors or resistors)?

Answer 29

Capacitors

Question 30

What happens to the bronchial arteries in CF?

Answer 30

Increase in size

Question 31

What is the effect of persistent hypoxic vasoconstriction?

Answer 31

Vascular structural remodeling, leading to pulmonary arterial HTN (PAH)

Question 32

In normal upright subjects at rest, blood flow (BLANKS) from the apex of the lung to the base of the lung.

Answer 32

In normal upright subjects at rest, blood flow INCREASES from the apex of the lung to the base of the lung.

Question 33

Are the effects of gravity felt equally in pulmonary veins and arteries?

Answer 33

Yes

Question 34

Where is pulmonary edema seen in the lungs? Why?

Answer 34

Lower lobes d/t increase flow of blood there relative to the other parts

Question 35

What is the effect of positive pressure ventilation on the upper part of the lungs (zone 1) relative to the Pa and PA?

Answer 35

PA >>>Pa, meaning that arteries could collapse

Question 36

How permeable are pulmonary capillaries to proteins? What is the consequence of this?

Answer 36

Very Higher propensity to develop interstitial edema

Question 37

The capillary pressure in the pulmonary circulation favors what (filtration or reabsorption? What is the consequence of this?

Answer 37

Filtration Thus lymphatics play a large role in pumping out this excess fluid

Question 38

Why is there a negative hydrostatic pressure in the pulmonary interstitium? When can this become positive?

Answer 38

Lung expansion lowers it Can become positive if there is inflammation of the capillaries

Question 39

Which way does fluid flow between the alveoli and the interstitium? Why?

Answer 39

From alveoli to the interstitium d/t lower pressure in the interstitium

Question 40

What is the effect of an increase in intravascular hydrostatic pressure in the pulmonary circulation?

Answer 40

Pulmonary edema

Question 41

What is the effect of an decrease in capillary osmotic pressure in the pulmonary circulation?

Answer 41

Pulmonary edema

Question 42

What is the effect of an increase in capillary permeability in the pulmonary circulation?

Answer 42

Pulmonary edema

Question 43

In regions of dead space, alveolar gas has what composition relative to the inspire humidified air?

Answer 43

Same (all oxygen, no CO2)

Question 44

When do right to left shunts occur?

Answer 44

If there is a defect in the | wall between the right and left ventricles

Question 45

A defining characteristic of the hypoxemia caused by a right-to-left shunt is that it cannot be corrected by having the person breathe a high O2 gas (e.g., 100% O2). Why?

Answer 45

because the shunted | blood never goes to the lungs to be oxygenated.

Question 46

Do left to right shunts cause hypoxemia? Why or why not?

Answer 46

No, because oxygenated blood flows into right ventricle to be oxygenated again.

Question 47

What are the causes of a left-to-right shunt? (2)

Answer 47

Patent ductus arteriosus or traumatic injury