RS: ventilation, perfusion & VQ relationship

Question 1

what is ventilation?

Answer 1

process by which air moves in and out of lungs

Question 2

what is perfusion?

Answer 2

process by with deoxygenated blood passes through the lung and becomes oxygenated

Question 3

what is the relationship between ventilation and perfusion called?

Answer 3

V/Q ratio

Question 4

what 3 things affect the distribution of ventilation?

Answer 4

gravity
compliance
resistance

Question 5

how does gravity effect the distribution of ventilation?

Answer 5

gravity pulls lung down and away from chest wall.

Question 6

what is the difference in pleural pressure, alveolar pressure and transpulmonary pressure at the apex and base of the lung?

Answer 6

pleural pressure more negative at apex
trans pulmonary pressure greater at apex
alveolar volume increased

Question 7

how does compliance affect the distribution of ventilation in the lung?

Answer 7

high compliance means that the lungs and chest wall expand easily

Question 8

what is compliance?

Answer 8

how much effort is required to stretch the lungs and chest wall

Question 9

decreased compliance is common in pulmonary conditions such as:

Answer 9

1. scarring of lung tissue (tuberculosis)
2. lungs filled with fluid (edema)
3. deficiency in surfactant production
4. destruction of elastic fibres (emphysema)

Question 10

what is resistance?

Answer 10

any narrowing or obstruction of the airway that might reduce airflow

Question 11

how does resistance affect the distribution of ventilation?

Answer 11

large diameter airways have decreased resistance

Question 12

increased resistance is common in pulmonary conditions such as:

Answer 12

1. asthma
2. COPD (emphysema, chronic bronchitis) due to obstruction or colapse of airways

Question 13

what is anatomical dead space?

Answer 13

volume of gas in each breath that does not participate in gas exchange eg. alveoli that are perfused but not ventilated

Question 14

what is physiological dead space?

Answer 14

total volume of gas in each breath that does not participate in gas exchange eg. alveoli that are perfused but not ventilated

Question 15

what is the pulmonary circulation of the lungs?

Answer 15

brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart
- low resistance

Question 16

what is the bronchial circulation of lung

Answer 16

brings oxygenated blood to lung parenchyma

Question 17

what circulation is more affected by gravity?

Answer 17

pulmonary - low pressure, low resistance

Question 18

in pulmonary blood flow does the base or the apex get better blood flow?

Answer 18

base

Question 19

what is the V/Q ratio in the lung?

Answer 19

total alveolar ventilation
divided by
capillary flow

Question 20

what is the V/Q ratio in a single alveolus?

Answer 20

alveolar ventilation
divided by
capillary flow

Question 21

what is the alveolar ventilation, pulmonary blood flow and V/Q for lung?

Answer 21

alveolar ventilation = 4-6 L/min
pulmonary blood flow = 5 L/min
V/Q for lung = 0.8-1.2

Question 22

what is the V/Q when ventilation exceed perfusion?

Answer 22

> 1

Question 23

what is the V/Q when perfusion exceeds ventilation?

Answer 23

< 1

Question 24

in a ‘perfect’ model, inspired gas and cardiac output shared equally between alveoli V/Q =?

Answer 24

1

Question 25

what is arterial hypoxemia?

Answer 25

arterial PO2 < 80mmHg (normally 100)

Question 26

what is hypoxia?

Answer 26

when insufficient O2 to carry out metabolic functions - when arterial PO2 < 60 mmHg

Question 27

what is hypercapnia?

Answer 27

increase in arterial PPCO2>40mmHg

Question 28

what is hypocania?

Answer 28

decrease in arterial PCO3<35mmHg

Question 29

what is an anatomical shunt?

Answer 29

usually in the lung
- blood from right atrium or ventricle crosses over septum to left atrium or ventricle (right to left shunt)

Question 30

in a right to left shunt, is the blood oxygenated or deoxygenated?

Answer 30

deoxygenated

Question 31

how does an anatomical shunt affect PO2?

Answer 31

varies depending on the size of shunt

Question 32

how does an anatomical shunt effect the alveolar ventilation and the distribution of blood flow?

Answer 32

alveolar ventilation = same
distribution of blood flow = changed

Question 33

what does a physiological shunt?

Answer 33

ventilation to lung units is absent in presence of continuing perfusion (venous admixture)

Question 34

what happens to alveolar ventilation and the distribution of blood flow in a physiological shunt?

Answer 34

alveolar ventilation = different
distribution of blood flow = same

Question 35

what is atelectasis?

Answer 35

obstruction of ventilation due to mucous plugs, airway oedema, foreign bodies, tumour in airways

Question 36

what is the most common cause of arterial hypoxemia in patients with respiratory disorders?

Answer 36

V-Q mismatching

Question 37

what does V- Q mismatching result in?

Answer 37

alveolar and capillary gas contents varying

Question 38

what is chronic obstuctive pulmonary disease? COPD

Answer 38

• condition where airflow is obstructed
• encompasses emphysema and chronic bronchitis

Question 39

what causes chronic obstuctive pulmonary disease and what are the symptoms? COPD

Answer 39

cause = long term smoking
symptoms = chronic cough, chest tightness, shortness of breath, increases mucous production

Question 40

what is emphysema?

Answer 40

• structures in alveoli over inflated
• longs loose elasticity and can’t fully expand or contract
• patients can inhale but exhalation is difficult due to decreased elastic recoil

Question 41

what is chronic bronchitis?

Answer 41

• inflammation of bronchi causing mucous production and excessive swelling
• shortness of breath with mild exertion
• chest infection more prevalent

Question 42

what is pulmonary fibrosis?

Answer 42

• type of lung disease
• scarring and thickness of tissue
• decreased elasticity
• decreased gas exchange