Ventilation/Perfusion Flashcards
Pulmonary circulation
pulmonary artery has
deoxygenated blood
Pulmonary circulation
pulmonary vein has
oxygenated blood
The Pulmonary Circulation feeds into
the areas where gas exchange occurs
Bronchial circulation:
bronchial arteries deliver
oxygenated blood to larger lung structures
Bronchial circulation
deoxygenated blood from larger lung structures (tacheobronchial tree, pulmonary nerves, smooth muscle, etc) is collected by the
azygos and intercostal veins and sent to right atrium
Bronchial circulation
pulmonar and cronchial circulations are interconnected. these junctions are called
anastomoses
Bronchial circulation
oxygenated blood mixing with de-oxygenated blood is termed
“left to right shunt”
Bronchial circulation
when deoxygenated blood mixes with oxygenated arterial blood, it is called a
“right to left shunt”
Consequence of Right to Left Shunt or mixing of oxygenated and deoxygenated blood
PO2 will be lower than expected
Pulmonary Blood Pressure
Since the mean pulmonary pressure is much ___ than the mean aortic pressure
lower;
the walls of the pulmonary artery and its branches are much thinner and contain much less smooth muscle and elastin than the walls of the aorta
pulmonary arterioles are very
thin and contain little smooth muscle
systemic arterioles have very thick walls composed mainly of
circularly arranged smooth muscle
the pulmonary arterioles do not have the same capacity for___ as systemic arterioles
vasocontriction
because cardiac output is high, and P is low, this means
that R (resistance of pulmonary circulation) is very low
almost 1/10th that of the systemic vascular resistance
Gravity creates regional differences in pulmonary blood flow by two mechanisms:
- hydrostatic pressure
- starling resistors
Hydrostatic pressures
the pulmonary arterial and venous blood pressure are both ___ at the lung apex and ___ at the base of the lungs
lower; higher
Starling resistors
if alveolar pressure PA is low (no compression of the capillary), blood flow is determined by
arterial pressure (Pa) and venous pressure (Pv)
Starling resistors
when alveolar pressure PA > Pv (collapsed capillary)
blood flow is determined by arterial pressure and alveolar pressure
we see starling effect at the
apex of lung
Pulmonary capillaries are referred to as
alveolar vessels
flow through these vessels is determined by relationship between the alveolar pressure and pressure within them
larger pulmonary vessles that run through the lung parenchyma are exposed to radial traction. they are enlarged with inhalation and are called:
extra-alveolar vessels
the caliber of the extra-alveolar vessels is greatly affected by lung volume bc this determines the expanding pull of parenchyma
Hypoxia (low PO2) induces
pulmonary vasoconstriction. this directs the blood flow away from the hypoxic region of the lung
this is seen in ppl with pneumonia
in systemic capillaries, local areas of hypoxia will cause a
localized vasodilation, increasing blood flow to that region
Regional differences in ventilation are due to gravity:
at apex, airways are ___ and intrapleural pressure is ___
more open; more negative
Regional differences in ventilation are due to gravity:
at base, airways are ___ and intrapleural pressure is ___
compressed; less negative
Ventilation and Perfusion:
at the apex of the lung, V/Q is
> 1
Ventilation and Perfusion:
at base of the lung, V/Q is
<1
the apex of the lungs is relatively ___ while the base of the lungs is relatively ___
over-ventilated; over-perfused
radial traction is ___ at the apex
greater
hydrostatic pressure within pulmonary capillaries is greater at the ___ of the lung
base
blow flow is greater at the base of the lung bc of
Pa>Pv>PA
at alveoli in the apex, a lack of perfusion means
we only add small amount of oxygen to blood and small amount of CO2 removed
at alveoli in base, under ventilating and over perfusing
low PO2
more oxygen is added to the blood at the base
more CO2 is removed from body
apex intrapleural pressure is ___ negative
more; as compared to the base
apex receives ___ tidal volume than the base
less
