Pulmonary Circulation

Question 1

What kind of bloods does the pulmonary artery carry?

Answer 1

oxygen deficient blood to the lungs

Question 2

What kind of blood does the pulmonary vein carry?

Answer 2

oxygen-rich blood to the heart (left artery)

Question 3

What are the functions of pulmonary circulation?

Answer 3

1. Gas exchange (oxygen and carbon dioxide)
2. filter - can capture/trap emboli into the lung (better than being trapped in the brain)
3. blood reservoir for left ventricle - decrease load on LV
4. nutrient supply - pulmonary circulation and bronchial circulation

Question 4

What are physiological factors that determine the effect of inhaled drug therapy?

Answer 4

1. aerosal particle size and permeability
2. airway geometry (does the drug get to alveoli)
3. pulmonary circulation (drug absorption)
4. lung clearance mechanisms
5. underlying lung disease

Question 5

describe pulmonary vessels

Answer 5

1. pulmonary artery 30% the thickness of the aorta
2. flexible and distensible
3. capillaries are numerous with multiple branches and anastomoses - each alveolus sits in a capillary basket

Question 6

what is the mean systemic pressure in the arteries?

Answer 6

100mmHg

*highest pressure is 120 and goes down to 0 when empty

Question 7

What is the mean pulmonary pressure ?

Answer 7

15 mmHg

*goes up to 25 during systole

Question 8

what 2 circulations are the lungs perfused by?

Answer 8

1. pulmonary circulation

2. bronchial circulation

Question 9

what kind of blood do bronchial arteries carry?

Answer 9

provide systemic blood to the lung tissue which arise from the aorta and enter the lungs and supply the lung tissue except the alveoli

Question 10

What does V stand for?

Answer 10

ventilation (air);

1. indicates effective minute ventilation of aerated pulmonary alveolar gas exchange surface with oxygenated gas
2. need both alveolar recruitment and adequate respiratory activity

*amount of air that goes to lung

Question 11

What does Q stand for?

Answer 11

Perfusion (blood);

1. flow volume per unit time
2. indicates proportion of cardiac output that perfuses pulmonary circuit
3. commonly extrapolated by determining pulmonary vascular resistance

*amount of blood that goes to the lung. What effects perfusion is the amount of oxygen rather than cardiac output

Question 12

hypoxic alveolus

Answer 12

1. hypoventilation
2. V/Q mismatch
3. worsening hypoxia
4. pulmonary vascular constriction

This leads to respiratory failure, acidosis, circulatory failure

Question 13

well ventilated alveolus

Answer 13

1. oxygen tension rises
2. endothelial NO synthesis
3. relaxation of pulmonary vessels

Good gas exchange (V + Q are matched)

Question 14

what is the formula for minute ventilation?

Answer 14

min vent = vol. (ml) air breathed in & out/min

Question 15

what is the formula for pulmonary ventilation?

Answer 15

pul. vent = Tidal Vol (ml) x resp. rate (breaths/min)

Question 16

What is alveolar ventilation?

Answer 16

1. more important than pulmonary ventilation
2. the volume of air exchanged between the atmosphere and the alveolar per minute
3. less than pulmonary ventilation due to “anatomic dead space”

Question 17

What is anatomic dead space?

Answer 17

the volume of air in conducting airways that is not available for gas exchange (~150 ml in adults)

Question 18

What is the formula for alveolar ventilation?

Answer 18

(TV - dead space) x resp. rate

Question 19

what happens to alveolar ventilation during deep slow breathing compared to quiet breathing at rest? What happens to pulmonary ventilation?

Answer 19

Alveolar ventilation is highest during deep slow breathing compared to quiet slow breathing at rest because deeper breathing means a larger tidal volume.

pulmonary ventilation remains the same for quite breathing and deep slow breathing

Question 20

Vessel diameter is influenced by what extra vascular forces?

Answer 20

1. gravity
2. body position
3. lung volume
4. alveolar pressures/intrapleural pressures
5. intravascular pressures

Question 21

what is the formula for pulmonary vascular resistance?

Answer 21

PVR = Ppulm/Qpulm

PVR = (Ppa - Pla)/ CO

Question 22

describe flow of blood in zone 1 of the lung

Answer 22

may be absent because there is inadequate pressure to overcome alveolar pressure

Question 23

describe flow of blood in zone 3 of the lung

Answer 23

continuous and driven by the pressure in the pulmonary arteriole - pulmonary venous pressure

Question 24

describe flow of blood in zone 2 of the lung

Answer 24

may be pulsatile and driven by the pressure in the pulmonary arterior - alveolar pressure (collapsing the capillaries)

Question 25

define shunted ventilation

Answer 25

A perfused part of the lung is not adequately ventilated

Question 26

alveolar deadspace ventilation

Answer 26

a ventilated part of the lung is not adequately perfused

Question 27

What can cause alveolar deadspace ventilation?

Answer 27

pulmonary embolism, pulmonary hypertension

Question 28

what can cause shunted ventilation, leading to V and Q mismatch?

Answer 28

pneumonia, pulmonary edema, atelectasis (partial or complete collapse of the lung)

Question 29

When is PVR (pulmonary vascular resistance) lowest and highest?

Answer 29

Pulmonary vascular resistance is lowest near the FRC (functional residual capacity) and increases at both high and low lung volumes.

Question 30

compare degree of perfusion in various parts of the lung

Answer 30

apex: good ventilation; perfusion poor due to gravity and pressure effect of alveolar inflation

mid lung: ventilation + perfusion well matched

lower lung: perfusion better due to gravity

basal lung: perfusion squashed by high interstitial pressure