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Ventilation (V) & Perfusion (Q) (coupling of V&Q (V > Q (ex:…
Ventilation (V) & Perfusion (Q)
local regulation
lung perfusion:
blood flow
alveolar arterioles constrict when the local PO2 is low
blood is rerouted to a high PO2 area b/c the blood is there to pick up O2
alveolar ventilation:
airflow
bronchioles increase in diameter when CO2 increases b/c the purpose of the conducting zone is to direct CO2 generated by tissue out of the airway
coupling of V&Q
ventilation = amount of gas reaching the alveoli
perfusion (Q) = blood flow reaching the alveoli
V and Q rates must be matched for optimal and efficient gas exchange
V > Q
ex:
pulmonary thrombosis (vessel plug)
ex:
exercise
perfusion is impeded
V < Q
ventilation is impeded
ex
: COPD
V-Q is never balanced for all alveoli b/c
mucus can plug alveolar ducts
gravity can effect blood flow & air flow
influences
CO2
local PO2
effect:
changes perfusion
changes in PO2 in alveoli cause changes in the diameters of the pulmonary arterioles
alveolar PO2 high = arterioles dialate
alveolar PO2 low = arterioles constrict
opposite mechanism is seen in systemic arterioles that dilate when PO2 is low and constrict when PO2 is high