Ventilation, Perfusion Flashcards
Systemic Circulation
arteries: oxygenated
veins: deoxygenated
oxygenated blood from left ventricle to tissues
deoxygenated blood from tissues to right atrium
Pulmonary circulation
arteries: deoxygenated
veins: oxygenated
Pulmonary artery 1 for each lung
Pulmonary vein 2 for each lung. Inferior and superior.
carries deoxygenated blood away from right ventricle to the lungs
pulmonary trunk -> pulmonary artery left/right -> hilum lung and bronchus circulation -> pulmonary arterioles -> pulmonary capillaries around alveoli
returns oxygenated blood to left atrium. pulmonary capillaries -> pulmonary venules -> pulmonary vein
Veins >< arteries
veins: blood towards heart
arteries: blood away from heart
Bronchial circulation
complementary to pulmonary circulation
terminal bronchioles; pleura;large pulmonary vessels
supply nutrients and oxygen to lungs.
Aorta -> bronchial arteries -> bronchial vessels -> trachea and bronchi -> bronchial veins (or shunt: pulmonary veins, then deoxygenated blood gets into oxygenated blood) -> superior vena cava
Shunts
ventilated but not perfused
2% of blood bypass the circulation
blood to heart muscles -> enter besian veins in heart walls -> right atrium or instead shunt: drain directly in lumen and can be in left ventricle
bronchial arteries -> oxygen to bronchi -> deoxygenated go to bronchial veins or shunt: pulmonary veins that normally contain oxygenated blood
Airway obstruction
Blood diverted to better ventilated area
Ductus arteriosus
Shunt during fetal development
that goes from the pulmonary trunk to the aortic arch
no pulmonary circulation
oxygenated blood from placenta -> vena cava -> pulmonary trunk -> aortic arch
It then closes
V/Q
V is ventilation: amount of air reaching alveoli -> exchange gazes. influence: gravity
Q is perfusion: pulmonary blood flow reaching pulmonary arteries -> carries dissolved gazes. influence: position relative to heart -> pressure up -> perfusion up
V/Q is the ratio. How effective gaz exchange is. Idea would be 1.05. In practice it is 0.8
Upright and rest = 4(L/min)/5(L/min)
Highest V/Q ratio at the apex: lowest ventilation and blood flow.
Lowest V/Q ration at the base: highest ventilation and perfusion.
Gravity & weight: pleural pressure up -> alveolar volume down -> more compliant -> ventilation
Apex: PaO2 up (130mmHg), PaCO2 down (28mmHg)
Base: PaO2 down (88mmHg), PaCO2 up (42mmHg)
Base: more blood flow -> more gaz exchange.
Apex: more O2 exchange
V/Q ratio graph
x axis ribs from bottom to top
y axis is the lung volume and ventilation-perfusion ration
can see that at the bottom of the lung the blood flow is higher than the ventilation: V/Q the lowest
although both the blood flow and ventilation reduce towards the apex of the lungs the blood flow gets lower and lower than ventilation: V/Q the highest
Position relative to heart: under heart receive more BF
V/Q mismatch
Limited availability of O2 and CO2 -> Partial pressures change -> gaz exchange less efficient
Pulmonary embolism
clot block blood flow to lungs -> normal ventilation but lower perfusion -> V/Q goes up. If Q=0 then alveoli is a dead space (ventilation but no perfusion)
compensation: vasoconstriction/vasodilation.
Airway obstruction
Normal blood flow but no ventilation
paO2 down and paCO2 up
hypoxic vasoconstriction -> blood diverted to ventilated part -> Hb already saturated -> paO2 cant go up -> hyperventilation
Deep vein thrombosis
DVT
blood clot in deep vein : leg/pelvis
risk: obstruct right side of the heat with the clot that detaches: pulmonary embolism
causes: decrease blood flow, injury blood vessels, easy clotting (age), leg pooling
no venous return -> pressure goes up -> leakage interstium -> swollen and red
Pulmonary embolism
PE
blockage of the lung artery
can be a result of the deep vein thrombosis
if low D-dimer its not a pulmonary embolism
CT scan
white: bone absorb most xray
black/grey: fluid absorb little
