Lecture 23 Pulmonary Circulation

Question 0

characteristics of low pressure high flow system. what is its compliance

Answer 0

• Wall thickness of arterial artery is 1/3 of aorta

- pulmonary arterial tree has larger compliance (7 ml/mm Hg)

Question 1

What are the 2 circulations of the lungs?

Answer 1

1) high pressure, low flow: (oxygenated blood) from thoracic aorta to bronchial arteries to trachea, bronchial tree, adventitia
2) low pressure, high flow: (deoxygenated blood) pulmonary artery and branches to alveoli

Question 2

What is the pulmonary arterial pressure and its mean?
What is the left atrium pressure?
what is the pressure gradient created between the 2?

Answer 2

-pulmonary arterial pressure = 24/9 mean is 15 mm Hg
-left atrium pressure = 8 mm Hg
gradient = 7 mm Hg

Question 3

How much blood is in the pulmonary circulation in ml? % total blood volume in body? How much in pulmonary capillaries

Answer 3

• 450 ml blood pulm circulation
• 9% total blood volume in body
• about 70 ml in pulmonary capillaries

Question 4

Failure of left side of heart causes pressure build up in pulmonary circulation

Answer 4

increases BV b 100%
increases BP
mild systemic effect bc systemic BV is 9X of pulmonary system

Question 5

Physiologic Shunt: what % of blood in systemic arteries has bypassed the pulmonary capillaries and from where?

Answer 5

2% from lung parenchyma and wall of left atrium

Question 6

When oxygen concentration in alveoli is ____ % or more below normal what happens?

Answer 6

70. adjacent blood vessels constrict (possibly from alveolar epithelial cells)

Question 7

What are the three zones of blood distriubution

Answer 7

zone 1: no blood flow, alveolar air pressure is always above alveolar capillary pressure
zone 2: intermediate blood flow during systole only
zone 3: continuous blood flow

Question 8

What type of flow do the apices of the lung usually have

Answer 8

zone 2 flow

Question 9

Distensibility of pulmonary veins can increase blood volume by up to ___ mL

Answer 9

400 (released to circulation when person stands up)

Question 10

Results of obstructing blood supply to one normal lung

Answer 10

• Blood flow through other lung is doubled

- BC ofpassive dilation of pulmonary vessels, pulmonary pressure in lung is only slightly increased

Question 11

Agents that constrict pulmonary arterioles

Answer 11

Some prostaglandins
Epinephrine
Angiotensin II
Norepinephrine

Question 12

Agents that dilate pulmonary arteries

Answer 12

• isoproterenol

- acetylcholine

Question 13

Agents that constrict pulmonary venules

Answer 13

• Serotonin
• histamine
• E. Coli endotoxin

Question 14

Sympathetic vasoconstrictor nerve fibers

Answer 14

• decrease pulmonary blood flow by as much as 30%
• cervical sympathetic ganglia
• mobilize blood from pulmonary reserve to systemic system

Question 15

During heavy exercise blood flow through lungs increases by 4X-7X.

• this increases the number of open ____ up to ____
• ___ all ____ and increases flow rate up to ___
• ___ pulmonary arterial pressure

Answer 15

capillaries up to 3X
distends, capillaries, 2X
increases

Question 16

Why is pulmonary arterial pressure rise just a little even during max exercise?

Answer 16

• because the number of open capillaries is increased 3X
• all capillaries distend and increase flow rate by 2X

-this conserves energy of the right side of the hear

Question 17

Left sided heart failure

-left atrial pressure is usually never above ___ mm Hg

Answer 17

• 6 mm Hg
• blood begins to dam and left atrial pressure rises from 1-5 mm hg to 40-50 mm hg
• increases above 8 mm hg cause equal increase in pulmonary arterial pressure. above 30 mm hg =pulmonary edema develops

Question 18

Lung capillary fluid exchange

Answer 18

pulmonary capillary hydrostatic pressure = 7 mm hg
interstitial fluid osmotic pressure = -14
interstial fluid hydrostatic pressure = -8 (neg pressure)
total = 29
cap osmotic pressure = -28 so net 1 mm hg out

Question 19

Pulmonary edema occurs when pulmonary capillary pressure is >25 mm Hg. most common cause is?

Answer 19

• Left sided heart failure or mitral valve disease
• damage to pulmonary blood capillary membranes
• lethal pulmonary edema can occur fast (acute)
• chronic, slow onset and lungs can adjust

Question 20

Causes of plueral effusion (pumping of fluid from pleural space by lymphatics creates normal pressure of -7 mm Hg, if it becomes more postive (-4 mm Hg) lungs collapse

Answer 20

Plueral effusion is edema of plueral cavity
causes:
-blockage of lymphatic drainage from pleural cavity
-cardiac failure
-reduced plasma colloid osmotic pressure, and infection/inflammation

Question 21

Hypoxia does what to the pressure in pulmonary arteries

Answer 21

increases pressure by possible release of prostaglandin

Question 22

Constriction of vessels supplying poorly ventilated alveoli is from

Answer 22

• low alveolar pO2
• drop in pH due to accumulation of CO2
• decline in pH = vasoconstriction in pulmonary vessels which is opposite in other tissues

Question 23

Reduction of blood flow to portion of lung has what effect on pCO2 and vessel diameter?

Answer 23

lowers alveolar pCO2 which = constriction of the bronchi supplying that portion of the lung (not as much CO2 being dropped off there)