Principles of gas exchange Flashcards
Rate of diffusion is proportional to…
surface area x change in pressure
What is the pressure gradient in terms of gas exchange?
Diference in the partial pressures of the respective gases in the alveolus and the blood.
What is the universal gas equation?
pressure x volume = number of moles x R x temperature
What characteristic of the basal lamina of alveoli and capillaries facilitates gas exchange?
Alveoli and capillaries share a basal lamina
What is Dalton’s law?
partial pressure of a gas in a gas mixture = total pressure x fractional concentration of the gas
What is the partial pressure of oxygen at sea level?
21.3 kPa
Is the partial pressure of oxygen in the alveoli higher or lower than that in room air? Why?
Lower (13.7 kPa) because inspired air is humidified in the upper airway (the water ‘dilutes’ the O2), in the alveoli oxygen is taken up and CO2 added (again, ‘dilutes’ the O2), and the body consumes about 1.25 x more O2 molecules than it produces CO2
What is the partial pressure of water vapour?
6.3 kPa
What is the alveolar partial presure of CO2
5 kPa
Can dissolved molecules exert partial pressure?
No
Partial pressure of a gas in solution is _______to its solubility.
inversely proportional
What is the difference in solubility in water between oxygen and carbon dioxide?
CO2 is about 24x more soluble in water
Theoretically is CO2 or O2 transfer more efficient?
CO2 much more efficient
How would oxygen diffusing capacity be measured?
Alveolar PO2 - mean pulmonary capillary PO2
How is oxygen diffusing capcity measured in practice?
Using carbon monoxide diffusing capacity:
Alveolar PCO
Mean pulmonary capillary PCO is effectively 0 b/c v high affinity of CO for Hb.
