Pulmonary circulation and V/Q ratio

Question 1

What is the typical length of the pulmonary artery?

Answer 1

5 cm

Question 2

What are characteristics of the pulmonary artery?

Answer 2

Thin-walled
High compliance
Can accommodate 2/3 of SV of RV
Constrict in response to hypoxia

Question 3

What are the SBP, DBP, and MAP of the pulmonary A?

Answer 3

SBP - 25 mmHg
DBP - 8 mmHg
MAP - 15 mmHg

Question 4

What is the average pulmonary capillary pressure?

Answer 4

7 mmHg

Question 5

What is the average pressure of the pulmonary veins and L atrium?

Answer 5

2 mmHg, range of 1-5 mmHg

Question 6

What is the comparison of pulmonary circulatory pressure and systemic pressures?

Answer 6

Pulmonary is 1/6 of systemic, same as RV to LV

Question 7

What does regional pulmonary blood flow depend on?

Answer 7

The position relative to the heart
Base has more blood flow than apex while standing

Question 8

What are the characteristics of zone 1?

Answer 8

No blood flow
Alveolar pressure is higher than arterial pressure throughout every part of the cardiac cycle
Pathological and when breathing against PEEP

Question 9

What are the characteristics of zone 2?

Answer 9

Pulsatile flow
Systolic arterial pressure is higher than alveolar pressure, but diastolic is lower

Question 10

What are the characteristics of zone 3?

Answer 10

Continuous flow
Pulmonary arterial pressure is always higher than alveolar pressure

Question 11

When will pulmonary pressure increase in left sided heart failure?

Answer 11

When L atrial pressure rises by more than 7-8 mmHg

Question 12

What things can cause pleural effusion?

Answer 12

Blockage of lymphatics
Cardiac failure
Diminished capillary oncotic pressure
Damage to the capillary walls

Question 13

What is the effect of hypoxia on PVR?

Answer 13

SyNS increases PVR in the presence of hypoxia after smooth muscle remodeling

Question 14

What are stimuli that can cause active changes in PVR?

Answer 14

Alveolar hypoxia
Motor innervation
Circulating vasoactive substance

Question 15

How does exercise effect PVR?

Answer 15

Not much change because of the vessels distensibility and recruitment of additional vessels

Question 16

At what lung volume is the lowest PVR?

Answer 16

At FRC

Question 17

What are the functions of pulmonary circulation?

Answer 17

Gas exchange
Blood filter
Blood reservoir
Metabolism

Question 18

What is the effect of inspiration of circulation?

Answer 18

Decreased flow in alveolar vessels
Increased flow in extra-alveolar vessels
Decreased LA and LV pressures
Decreased SBP

Question 19

What is always a sign of inadequate alveolar ventilation?

Answer 19

Increased PaCO2

Question 20

What is the ideal V/Q ratio?

Answer 20

1.0

Question 21

What is the V/Q ratio at rest?

Answer 21

0.8

Question 22

What is ventilation at rest?

Answer 22

4.2 L/min

Question 23

What is perfusion at rest?

Answer 23

5.5 L/min

Question 24

What is the V/Q ratio when ventilation is adequate but there is no perfusion?

Answer 24

Infinity

Question 25

What is a normal A-aDO2?

Answer 25

Less than 10 mmHg

Question 26

Where is perfusion greater than ventilation in the lungs?

Answer 26

Base

Question 27

What is alveolar dead space?

Answer 27

Ventilation without perfusion

Question 28

What are causes of abnormal oxygenation?

Answer 28

Hypoventilation
Diffusion block/impairment
V/Q mismatch
Shunt

Question 29

What is a shunt in reference to V/Q ratios?

Answer 29

Perfusion without ventilation