Gas Exchange Flashcards
what is the arterial and alveolar partial pressure of CO2?
40
name the three factors that drive diffusion of gases
SA
permeability
gradient
what is the venous CO2 pressure?
46
what is the venous O2 pressure?
40
at a capillary, how quickly does gas exchange occur? how much time does it take for the blood to get from one end to the other in normal conditions?
about 0.25 seconds for exchange and takes 0.75 seconds to get from one end to the other
if it only takes 0.25 for gas exchange but blood is in capillary for 0.75 seconds, what is the other time for?
it is reserved for if blood is flowing faster like during exercise
does O2 bound to Hb exert partial pressure?
NO
despite having a lower gradient than O2, CO2 still diffuses quickly across the lungs..why?
lungs are very permeable to it
what does it mean for there to be perfusion limitation?
it means that the solute is permeates easily through the membrane and reaches high pressures quickly and is therefore not able to perfuse anymore after like 0.2 seconds at the alveoli
what molecule is perfusion limited?
N2O
what molecule is diffusion limited?
CO
what does it mean to be diffusion limited?
the molecule that is coming into the blood gets sucked up quickly by Hb and a gradient continues to exist and is therefore limited by the time of diffusion it experiences
are O2 and CO2 perfusion or diffusion limited?
perfusion limited
what molecule can we use to test the blood gas barrier diffusing capacity?
CO
what three things can cause misleading results on blood gas barrier tests?
anemia
carboxy-hb
oxyhemoglobin
pretty much anything that takes Hb away from the CO to bind to and lead it to hit perfusion limitation
