Chapter 38 - Pulmonary Circulation, Pulmonary Edema, Pleural Fluid

Question 1

How far does the pulmonary artery extends beyond the apex of the right ventricle?

Answer 1

5 centimeters

Question 2

What is different of the pulmonary arterial branches different from the systemic ones?

Answer 2

Pulmonary arteries branches are very short, their vessels have large diameters, are thin and distensible, giving the pulmonary arterial tree a large compliance (around 7m/mm Hg)

Question 3

What type of blood flows thru the bronchial arteries that originated from the systemic circulation?

Answer 3

Oxygenated blood, in contrast to the pulmonary arteries that have deoxygenated blood

Question 4

How much of total cardiac output goes to the small bronchial arteries that originated from the systemic circulation?

Answer 4

About 1-2 percent

Question 5

What is the systolic and diastolic pressure in the right ventricle of a normal human being?

Answer 5

About 25 mm Hg, About 0 to 1 mm Hg

Question 6

What is the systolic and diastolic pulmonary arterial pressure of a normal human being?

Answer 6

25 mm Hg, 8 mm Hg;

Question 7

What is the mean pulmonary arterial pressure of a normal human being?

Answer 7

15 mm Hg

Question 8

What is the mean pulmonary capillary pressure in a normal human being?

Answer 8

7 mm Hg

Question 9

How much is the blood volume of the lungs?

Answer 9

About 450 milliliters (9% of the total blood volume of the entire circulatory system)

Question 10

How much of the pulmonary blood is in the pulmonary capillaries?

Answer 10

About 70 milliliters

Question 11

What happens during hypoxia in the lungs?

Answer 11

The capillaries vasoconstrict (more than 5x in very low O2 levels). This is opposite to the effect observed in systemic vessels.

Question 12

What is the pulmonary arterial pressure in the uppermost and lowest portion of the lung of a standing person?

Answer 12

About 15 mm Hg less than the pulmonary arterial pressure at the level of the heart, about 8 mm Hg greater

Question 13

What are Zones 1, 2, and 3?

Answer 13

Made up sections of the heart that are classified by the level of pulmonary blood flow.

Question 14

What is happening in Zone 1?

Answer 14

No blood flow during all portions of the cardiac cycle.

Alveolar pressure > Arterial pressure > Venous pressure

Question 15

What is happening in Zone 2?

Answer 15

Intermittent blood flow

Arterial pressure > Alveolar pressure > Venous pressure

Question 16

What is happening in Zone 3?

Answer 16

Continuous blood flow

Arterial pressure > Venous pressure > Alveolar Pressure

Question 17

When does Zone 1 blood flow occurs?

Answer 17

Only under abnormal conditions such as when pulmonary systolic arterial pressure is exceedingly low (hemorrhage).

Question 18

What happens in the blood flow through the lungs during heavy exercise?

Answer 18

Increase 4 to 7 fold.

Question 19

How is the extra flow of blood accommodated in the lungs during heavy exercise?

Answer 19

1. By increasing the number of open capillaries
2. By distending all the capillaries and increasing the rate of flow thru each capillary more than twofold.
3. By increasing the pulmonary arterial pressure.

Question 20

What changes occur to the pulmonary arterial pressure during heavy exercise?

Answer 20

The opening of additional capillaries and its distension decrease pulmonary vascular resistance so much that the pulmonary arterial pressure rises very little, even during maximum exercise.

Question 21

The left arterial pressure in a healthy person almost never rises above what pressure (even during the most strenuous exercise)?

Answer 21

+6 mm Hg

Question 22

What happens to the left arterial pressure as a result of left side heart failure?

Answer 22

Blood begins to dam up in the left atrium, causing the pressure to rise to 40 to 50 mm Hg.

Question 23

At what left arterial pressure would we see edema beginning to happen?

Answer 23

+ 30 mm Hg

Question 24

Why is it that the capillary blood flow in the alveolar walls describes as a “sheet of flow”?

Answer 24

Because in most places, the capillaries almost touch one another side by side.

Question 25

What is the pulmonary capillary pressure?

Answer 25

Around 7 mm Hg.

Question 26

How long does blood stay in the pulmonary capillaries?

Answer 26

Around 0.8 seconds, 0.3 seconds when cardiac output increases.

Question 27

What are some quantitative differences between peripheral and pulmonary capillaries?

Answer 27

1. Pulmonary pressure is low ( 7 mm Hg in lung compared to 17 mm Hg in peripheral)
2. The interstitial fluid pressure in the lungs is slightly more negative (-8 mm Hg in lung compare to the -5 mm Hg in peripheral)
3. Pulmonary capillaries are relatively leaky to protein molecules. Colloid osmotic pressure 14 mm Hg in lung compared to 7 mm Hg in peripheral.

Question 28

What is the net outcome of the interrelations between interstitial fluid pressure and other pressures in the lungs?

Answer 28

A net filtration

Question 29

How is the alveoli kept dry?

Answer 29

The slight negative pressure in the interstitial spaces maintained by the pulmonary capillaries and the pulmonary lymphatic system. Any extra fluid that appears in the alveoli is sucked mechanically into the lungs interstitium.

Question 30

What are some of the most common causes Pulmonary Edema?

Answer 30

1. Left-sided heart failure or mitral valve disease.
2. Damage to the pulmonary blood capillary membranes caused by infections such as pneumonia or by breathing noxious substances such as chlorine or sulfur dioxide.

Question 31

What is the pulmonary edema safety factor?

Answer 31

Pulmonary capillary pressure normally must rise to a value at least equal to the colloid osmotic pressure of the plasma inside the capillaries before significant pulmonary edema will occur. Around 21 mm Hg.

Question 32

What is the safety factor in chronic conditions?

Answer 32

When pulmonary capillary pressure remains elevated chronically (for at least 2 weeks), lungs become even more resistant to pulmonary edema because the lymph vessels expand greatly, increasing their capability of carrying fluid away by as much as 10 fold.

Question 33

Describe the pleural membrane

Answer 33

A porous, mesenchymal, serous membrane thru which small amounts of interstitial fluid transude continually into the pleural space, carrying with them tissue proteins, giving the pleural fluid a mucoid characteristic, which allows extremely east slippage of the moving lungs.

Question 34

How is negative pressure in the normal pleural space achieved?

Answer 34

Pumping of fluid from the space by the lymphatics (which is also the basis of the negative pressure found in most tissue spaces of the body).

Question 35

What pressure must the pleural fluid pressure always be on to keep the lungs expanded?

Answer 35

At least – 4 mm Hg. Usually -7 mm Hg.

Question 36

What is pleural Effusion?

Answer 36

The collection of large amounts of free fluid in the pleural space.

Question 37

What causes pleural effusion?

Answer 37

1. Blockage of lymphatic drainage from the pleural cavity.
2. Cardiac failure, which causes excessively high peripheral and pulmonary capillary pressures, leading to excessive transudation of fluid into the pleural cavity
3. Greatly reduced plasma colloid osmotic pressure, thus allowing excessive transudation of fluid.
4. Infection or any other cause of inflammation of the surfaces of the pleural cavity, which breaks down the capillary membranes and allows rapid dumping of both plasma proteins and fluid into the cavity.