ventilation and perfusion

Question 1

what is ventilation?

Answer 1

process by which air moves in and out of lung

Question 2

what is perfusion?

Answer 2

process by which deoxygenated blood passes thru the lung and becomes oxygenated

Question 3

what is the relationship between ventilation and perfusion called?

Answer 3

V/Q ratio

Question 4

what is the V/Q ratio a major determinant of?

Answer 4

normal gas exchange so level of PO2 and PCO2 in blood

Question 5

why is ventilation not uniformly distributed in lung?

Answer 5

gravity

Question 6

where is pleural pressure more negative?

Answer 6

apex - not base

Question 7

what other pressure is higher at apex?

Answer 7

transpulmonary

Question 8

where is there increased alveolar volume?

Answer 8

apex

Question 9

what is compliance?

Answer 9

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

Question 10

what pulmonary conditions of decreased compliance a common feature of?

Answer 10

scarring in lung tissue, lung filled with fluid, deficiency in surfactant prod., destruction of elastic fibres (emphysema)

Question 11

what is resistance?

Answer 11

narrowing or obstruction of the airway that may reduce airflow

Question 12

what pulmonary conditions is increased resistance a feature of?

Answer 12

asthma, COPD

Question 13

what is anatomical dead space?

Answer 13

volume of gas during each breath that fills the conducting airways?

Question 14

what is physiological dead space?

Answer 14

total volume of gas in each breath that does not participate in gas exchange- ventilated not perfused

Question 15

which circulation is influenced by gravity?

Answer 15

pulmonary- greater flow to base than apex

Question 16

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

Answer 16

alveolar ventilation divided by capillary flow

Question 17

what is the V/Q ratio for a whole lung?

Answer 17

total alveolar ventilation divided by cardiac output

Question 18

what is alveolar ventilation in healthy individuals?

Answer 18

~4-6 L/min

Question 19

what is pulmonary blood flor in a healthy individual?

Answer 19

~5 L/min

Question 20

what is average V/Q value?

Answer 20

0.8-1.2

Question 21

what is V/Q when ventilation exceeds perfusion?

Answer 21

> 1

Question 22

what is V/Q when perfusion exceeds ventilation?

Answer 22

<1

Question 23

what is arterial hypoxemia?

Answer 23

arterial PO2 < 80mmHg

Question 24

what is hypoxia?

Answer 24

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

Question 25

what is hypercapnia?

Answer 25

increase in arterial CO2>40mmHG

Question 26

what is hypocapnia?

Answer 26

decrease in arterial PCO2 < 35 mmHg

Question 27

what is V/Q mismatching?

Answer 27

most frequent cause of arterial hypoxia in patients with respiratory disorders

Question 28

what is an anatomical shunt?

Answer 28

mixed venous blood directly into arterial blood- alveolar ventilation same, distribution of blood flow changed, PO2 varied depending on size

Question 29

where do most anatomical shunts occur and what does this result in?

Answer 29

in heart- RA/V to LA/V

results in varying degrees of hypoxia

Question 30

what is a physiological shunt?

Answer 30

ventilation to lung units in presence of continuing perfusion- venous mixture-alveolar ventilation different, distribution of blood flow same

Question 31

what blood mixes in a physiological shunt?

Answer 31

blood perfusing non-ventilated alveolus is mixed venous- mixes with arterial

Question 32

what occurs if V/Q = 0?

Answer 32

ventilation to a region is 0 eg blocked airway- ventilation redistributed to other alveoli

Question 33

what is the cause of low V/Q

Answer 33

asthma, chronic bronchitis

Question 34

what is the cause of high V/Q?

Answer 34

emphysema- distupted gas exchange

pulmonary fibrosis- decreased gas exchange

Question 35

what is COPD?

Answer 35

condition in which airflow is obstructed- emphysema and chronic bronchitis- cause long term smoking

Question 36

what is emphysema?

Answer 36

structures in alveoli over inflated- inhale but exhale difficult due to decreased elastic recoil

Question 37

what is chronic bronchitis?

Answer 37

inflammation of bronchi causing mucous production and excessive swelling, shortness of breath, chest infections more prevalent

Question 38

what is pulmonary fibrosis?

Answer 38

interstitial lung disease, scarring and thickening of tissue, decreased elasticity, decreased gas exchange