Pulmonary Physiology: Perfusion

Question 1

What are the two functional zones of the lungs and what do each do?

Answer 1

Conducting zone: Gets air into the distal structures, no gas exchange.

Respiratory zone: Gas exchange.

Question 2

Is the pulmonary vasculature low, or high pressure?

Answer 2

Low

Question 3

Name three characteristics of pulmonary vessels.

Answer 3

1. Larger diameters
2. Shorter, more branches
3. Large number of arterioles that have low resistance

Question 4

Describe the smooth muscle of pulmonary arterioles.

Answer 4

There is not as much –> high compliance, low resistance, allows for distension.

Question 5

As pulmonary arterial pressure increases, pulmonary resistance _________.

Answer 5

decreases

Question 6

In which part of the lungs is flow the highest?

Answer 6

Lower lungs (zone 3)

Question 7

What are the two ways the pulmonary vasculature accomodates increased flow?

Answer 7

1. Recruitment (upper lungs will get used)

2. Distension of the arterioles and capillaries

Question 8

How is alveolar vessel resistance affected by high intravascular pressure and low alveolar pressure?

Answer 8

Vessel resistance is decreased in this case

Question 9

How is alveolar vessel resistance affected by low intravascular pressure and high alveolar pressure?

Answer 9

Vessel resistance is increased in this case

Question 10

What happens to the extra-alveolar vessels in the lung parenchyma during inspiration?

Answer 10

They expand because they are pulled open by expansion of the surrounding tissue.

Question 11

Can expansion of alveoli compress alveolar capillaries?

Answer 11

Yeah

Question 12

When PO2 is less than 60mmHg, what happens to pulmonary vessels? How does this differ from systemic vessels?

Answer 12

Pulmonary vessels constrict. Systemic vessels dilate in response to hypoxia.

Question 13

What is the advantage to having pulmonary vessels constrict in response to hypoxia? Is this a neural, or metabolic function?

Answer 13

It shunts blood to alveoli that are actually being ventilated and that is good. It is a metabolic function.

Question 14

In which lung zone (1, 2, or 3) is pulmonary blood flow intermittent?

Answer 14

Zone 2

Question 15

What is pulmonary wedge pressure used to measure?

Answer 15

Left atrial pressure

Question 16

Pulmonary capillary fluid flow is determined by the balance between _________ and ________ pressures.

Answer 16

hydrostatic and osmotic

Question 17

What are the three ways in which interstitial fluid in the lungs is removed?

Answer 17

1. Alveolar vaporization
2. Venule resorption
3. Lymphatic drainage

Question 18

Pulmonary hypertension is defined as greater than _____mmHg of mean ARTERIAL pressure.

Answer 18

25

Question 19

Name one heart condition that can cause pulmonary hypertension.

Answer 19

ventricular septal defect

Question 20

Which three mechanisms cause pulmonary hypertension?

Answer 20

1. Increased pulmonary flow relative to systemic flow (like with a VSD).
2. Increased pulmonary resistance from vasoconstriction.
3. Increased left atrial pressure causes a back-up into the pulmonary circulation (left heart disease).

Question 21

Pulmonary pressure will increase to greater than 25mmHg when pulmonary flow:systemic flow exceeds __:1

Answer 21

1.5:1

Question 22

Pulmonary edema occurs when CAPILLARY pressure exceeds _____mmHg.

Answer 22

25mmHg

Question 23

What are the three steps in the progression of pulmonary edema?

Answer 23

1. Flooding of peri-capillary interstitial spaces.
2. Crescentic filling of the alveoli.
3. Flooding of individual alveoli with loss of gas exchange.

Question 24

How does ARDS cause pulmonary edema even at normal capillary pressures?

Answer 24

Increased vascular permeability.

Question 25

Some bronchial veins join with _______ veins, which lowers PO2 in the blood traveling to the left atrium.

Answer 25

pulmonary

Question 26

Why doesn’t blood go into fetal lungs? How does blood flow in the fetal heart?

Answer 26

There is complete vasoconstriction in pulmonary vessels (very high resistance). Blood instead is shunted from the right heart to the left through the foramen ovale (an atrial septal hole) or it goes from the pulmonary artery into the aorta through the ductus arteriosus.

Question 27

After birth, what happens to pulmonary resistance?

Answer 27

It drops!

Question 28

What is normal pulmonary blood pressure (systolic/diastolic)?

Answer 28

25/8 mmHg

Question 29

Is PGI2 released after birth to decrease pulmonary resistance?

Answer 29

Apparently yeah