Lung Physiology Flashcards
What does the respiratory pump do
generates negative intra-alveolar pressure
at what point is Hb fully saturated
25% of way through capillary
Which alveoli are preferentially ventilated at rest
alveoli at base
what capillaries are preferentially perfused with blood at rest
capillaries at most dependent parts of lungs
what happens in hypoxic mediated pulmonary vasoconstriction
blood is diverted away from areas without air; opposite of what would happen if skin was hypoxic
what is dead space
volume of air not contributing to ventilation
what is the volume of physiological dead space
175mls
what makes up physiological dead space
anatomical and alveolar dead space
what is the definition of physiological dead space
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
what is the volume of anatomical dead space
150mls
what is the volume of alveolar dead space
25mls
what is PaCO2
arterial CO2
what is PACO2
alveolar CO2
what is PaO2
arterial O2
what is PAO2
alveolar O2
what is PIO2
Pressure of inspired O2
what is V’A
alveolar ventilation
what is V’CO2
co2 production
how does air move
bulk flow; from high to low pressure
what is the alveolar gas equation (equation)
PAO2 = PiO2 - PaCO2/ R
what is the alveolar gas equation (in words)
alveolar pressure = pressure of inspired oxygen - (pressure of arterial CO2 divided by R)
what does PaCO2 in the alveolar gas equation approximate and why
alveolar carbon dioxide pressure due to rapid diffusion of CO2
what is R in the alveolar gas equation
respiratory quotient (0.8)
what is hypoxaemia
low PaO2
what are the causes of hypoxaemia
alveolar hypoventilation
reduced PIO2
V/ Q mismatch
Diffusion abnormality
what is an equation for PaCO2 (equation)
PaCO2 = k V’CO2/ V’A
what does PaCO2 relate to - in words
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
what does arterial PaCO2 depend on
a constant, production of CO2, alveolar ventilation - doesn’t relate to oxygen at all
what are physiological causes of high CO2
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
what is the thickness of the gas exchange membrane
approx. 1micron
what does gas exchange depend on
supply of bulk gas to alveoli and movement of blood
- has some active involvement
how many layers are there for gas exchange
7
what are the 7 layers for gas exchange
- alveolar epithelium
- tissue interstitum
- capillary endothelium
- plasma layer
- RBC membrane
- RBC cytoplasm
- Hb binding
What is Dalton’s Law
pressure exerted by each gas in a mixture is independent of pressure exerted by other gases
what are partial pressures directly proportional to
concentration
what is the total pressure of mix
sum of partial pressures
what is Boyle’s law
at constant temperature, the absolute pressure of a fixed mass of gas is inversely proptional to volume
what is Boyle’s law (equation)
P1V1 = P2V2
what is Henry’s law
amount of gas dissolved in liquid at given temperature is directly proportional to pressure of gas with which the liquid is in equilibrium
what is Laplace’s law
P = 2T/ R (P = pressure, R = radius, T = tension)
when is Laplace’s law important
surfactant
what is the alveolar gas equation; alveolar oxygen
PAO2 = PiO2 - (PaCO2/R)
what is the alveolar gas eqution; arterial O2
PaO2 = PAO2 - (A-aDO2)
- PaO2 = arterial O2
- PAO2 = alveolar O2
- A-aDO2= alveolar-arterial difference
what is A-aDO2
alveolar-arterial difference - O2 lost in diffusion due to physical barrier - 1kPa
