Lung Physiology

Question 1

What does the respiratory pump do

Answer 1

generates negative intra-alveolar pressure

Question 2

at what point is Hb fully saturated

Answer 2

25% of way through capillary

Question 3

Which alveoli are preferentially ventilated at rest

Answer 3

alveoli at base

Question 4

what capillaries are preferentially perfused with blood at rest

Answer 4

capillaries at most dependent parts of lungs

Question 5

what happens in hypoxic mediated pulmonary vasoconstriction

Answer 5

blood is diverted away from areas without air; opposite of what would happen if skin was hypoxic

Question 6

what is dead space

Answer 6

volume of air not contributing to ventilation

Question 7

what is the volume of physiological dead space

Answer 7

175mls

Question 8

what makes up physiological dead space

Answer 8

anatomical and alveolar dead space

Question 9

what is the definition of physiological dead space

Answer 9

volume of air in the trachea that does not contribute to gas exchange plus the volume of air in the alveoli that does not contribute to gas exchange

Question 10

what is the volume of anatomical dead space

Answer 10

150mls

Question 11

what is the volume of alveolar dead space

Answer 11

25mls

Question 12

what is PaCO2

Answer 12

arterial CO2

Question 13

what is PACO2

Answer 13

alveolar CO2

Question 14

what is PaO2

Answer 14

arterial O2

Question 15

what is PAO2

Answer 15

alveolar O2

Question 16

what is PIO2

Answer 16

Pressure of inspired O2

Question 17

what is V’A

Answer 17

alveolar ventilation

Question 18

what is V’CO2

Answer 18

co2 production

Question 19

how does air move

Answer 19

bulk flow; from high to low pressure

Question 20

what is the alveolar gas equation (equation)

Answer 20

PAO2 = PiO2 - PaCO2/ R

Question 21

what is the alveolar gas equation (in words)

Answer 21

alveolar pressure = pressure of inspired oxygen - (pressure of arterial CO2 divided by R)

Question 22

what does PaCO2 in the alveolar gas equation approximate and why

Answer 22

alveolar carbon dioxide pressure due to rapid diffusion of CO2

Question 23

what is R in the alveolar gas equation

Answer 23

respiratory quotient (0.8)

Question 24

what is hypoxaemia

Answer 24

low PaO2

Question 25

what are the causes of hypoxaemia

Answer 25

alveolar hypoventilation reduced PIO2 V/ Q mismatch Diffusion abnormality

Question 26

what is an equation for PaCO2 (equation)

Answer 26

PaCO2 = k V'CO2/ V'A

Question 27

what does PaCO2 relate to - in words

Answer 27

partial pressure in artery is inversey proportional to alveolar ventilation and is directly proportional to amount of CO2 produced, and is equal to a constant

Question 28

what does arterial PaCO2 depend on

Answer 28

a constant, production of CO2, alveolar ventilation - doesn't relate to oxygen at all

Question 29

what are physiological causes of high CO2

Answer 29

V' A reduced so reduced minute ventilation V' A reduced so increase dead space ventilation by rapid shallow breathing V' A reduced so increase dead space by V/ Q mismatch Increase CO2 production

Question 30

what is the thickness of the gas exchange membrane

Answer 30

approx. 1micron

Question 31

what does gas exchange depend on

Answer 31

supply of bulk gas to alveoli and movement of blood | - has some active involvement

Question 32

how many layers are there for gas exchange

Answer 32

7

Question 33

what are the 7 layers for gas exchange

Answer 33

- alveolar epithelium - tissue interstitum - capillary endothelium - plasma layer - RBC membrane - RBC cytoplasm - Hb binding

Question 34

What is Dalton's Law

Answer 34

pressure exerted by each gas in a mixture is independent of pressure exerted by other gases

Question 35

what are partial pressures directly proportional to

Answer 35

concentration

Question 36

what is the total pressure of mix

Answer 36

sum of partial pressures

Question 37

what is Boyle's law

Answer 37

at constant temperature, the absolute pressure of a fixed mass of gas is inversely proptional to volume

Question 38

what is Boyle's law (equation)

Answer 38

P1V1 = P2V2

Question 39

what is Henry's law

Answer 39

amount of gas dissolved in liquid at given temperature is directly proportional to pressure of gas with which the liquid is in equilibrium

Question 40

what is Laplace's law

Answer 40

P = 2T/ R (P = pressure, R = radius, T = tension)

Question 41

when is Laplace's law important

Answer 41

surfactant

Question 42

what is the alveolar gas equation; alveolar oxygen

Answer 42

PAO2 = PiO2 - (PaCO2/R)

Question 43

what is the alveolar gas eqution; arterial O2

Answer 43

PaO2 = PAO2 - (A-aDO2) - PaO2 = arterial O2 - PAO2 = alveolar O2 - A-aDO2= alveolar-arterial difference

Question 44

what is A-aDO2

Answer 44

alveolar-arterial difference - O2 lost in diffusion due to physical barrier - 1kPa