Ventilation and Perfusion

Question 1

what is ventilation

Answer 1

movement of gases in and out of the lungs through airways

it is measured as change in volume per unit of time eg 5.5L/min

Question 2

what is perfusion

Answer 2

blood flow through organs eg lungs

through blood besets measured as flow of blood / unit of time eg 650 ml/min

Question 3

describe the regional differences in lung ventilation

Answer 3

apical alveoli are about 4 times larger than basal alveoli in upright posture due to gravity
basal alveoli can therefore expand more and have better ventilation than apical areas

Question 4

describe the bronchial circulation of the lung

Answer 4

bronchial artery from the thoracic aorta
bronchial vein to the superior vena cava
takes up 2% of cardiac output

Question 5

what are the blood pressures in the pulmonary artery, aorta, pulmonary vein, superior vena cava

Answer 5

PA - 15-30/4-12
A - 100 - 140/60-90
PV - 2-15
SVC - 2-8

Question 6

what is the equation for cardiac output

Answer 6

HR x SV

Question 7

describe the process of blood vessels branching from the pulmonary artery to the lungs

Answer 7

splits into left and right , then into extra-alveolar vessels while running through lung parenchyma

Question 8

how many capillaries are there per alveoli approx

Answer 8

1000

Question 9

what is emphysema and how does it affect gas exchange

Answer 9

widespread destruction and dilation of distal airway
regional destruction of vascular beds
poor gas exchange and hypoxia
greatly reduced surface area

Question 10

where is the pulmonary circulation does gas exchange start

Answer 10

small arterioles

Question 11

what is hydrostatic pressure

Answer 11

force exerted by weight of fluid (blood/water) due to gravity ie max hydrostatic pressure at the bottom of a glass of water than at the top

Question 12

what is the difference in diameter of vessels in the lungs ie lung perfusion due to hydrostatic pressure

Answer 12

extra alveolar vessels: running through lung parenchyma, their diameter is affect by the lung volume
alveolar vessels - diameter dependant on many factors

Question 13

describe what happens to the blood vessels in the zone 1 at the apex of the lungs

Answer 13

alveolar pressure is greater than pulmonary artery pressure which is greater than pulmonary venous pressure and the blood vessels collapse halting flow
alveolar dead space - good ventilation but not perfusion of blood ie no gas exchange

Question 14

describe what occurs in terms of lung perfusion in zone 2 of the lungs

Answer 14

recruitment zone
higher pressure in the arterial due to higher hydrostatic pressure therefore blood flow is dependant on the arterial pressure and the alveolar pressure

Question 15

how would haemorrhage or positive pressure ventilation affect lung perfusion

Answer 15

H - drop in P-arterial

PPV - rise in P alveolar

Question 16

describe what happens in zone 3 of the lungs in terms of lung perfusion

Answer 16

distension zone
lung bases
hydrostatic forces raise and pressure in the arterial and venous are greater than in the alveolus therefore there is continuous blood flow

Question 17

what is ventilation perfusion mismatch (V), (Q)

Answer 17

V/Q ratio
if the amount of ventilation Va to an area of lung is equal to the amount of perfusion Q the ration of Va/Q would be 1 - ideal situation
but the ratio varies from 3.3 at the apex of the lungs to 0.6 at the base - the normal average is 0.8

Question 18

what is the V/Q ratio in zone 1

Answer 18

infinity or very high as good ventilation but poor perfusion

Question 19

what is the equation for physiological dead space

Answer 19

anatomic dead space + alveolar dead space

Question 20

what are the 3 types of dead space

Answer 20

anatomic dead space - conducting airways - no gas exchange (150ml approx)
alveolar dead space - unperfused areas
physiological - each breath that does not take part in gas exchange

Question 21

what is a pulmonary embolism

Answer 21

blood clot from another area of the body which gets trapped in the lungs blocking blood supply
commonly from deep veins in the leg or pelvis
CAUSES ENLARGED DEAD SPACE

Question 22

what is a shunt in the lungs

Answer 22

where there is bypass of gas exchange and no ventilation occurs but good perfusion ie V/Q is zero

Question 23

what diseases cause pulmonary shunt

Answer 23

bronchial veins
pneumothorax
age related changes: areas low V/Q ration in the lungs

Question 24

what is pneumothorax and how is it treated

Answer 24

air in the cavity between the lungs and chest wall causing lung collapse
treated by immediate needle decompression - chest drain connected to an underwater sealed system

Question 25

which lung abnormality of oxygenation are you most likely to see in pneumonia

Answer 25

shunt