Pulmonary Blood flow Flashcards
Alveolar Capillaries
Arise from the right ventricle
• Are involved in the exchange of O2 and CO2 between
the blood and the air
• Millions of alveolar capillaries make is so the alveoli are
effectively a sheet of capillaries
Extra-Alveolar Capillaries
Arise from the left ventricle
• Deliver oxygen and CO2 to the tissue of the lungs
• Return to the heart in the pulmonary veins (venous
admixture)
o Reduces the PaO2 of the arterial blood by a few mm Hg.
o Increases the PaCO2 to a small degree.
PaO2 of alveolar capillary and extra alveolar capillary
aveolar- low
extra-alveolar-high
PaCO2 of alveolar capillary and extra alveolar capillary
aveolar- high
extra-alveolar-low
Function of alveolar capillary
Gas exchange
function of extra-alveolar capillary
Provide nutrients/remove waste from the tissue of
the lungs
blood gases alveolar capillary
High PaO2/Low PaCOw
blood gases extra alveolar capillary
Low PaO2/High PaCO2
*venous admixture
calculate pulmonary vascular resistance
PBP = COxPVR
pulmonary vascular resistance relative to systemic
must be about ¼ of the systemic.
How is Pulmonary vascular resistance determined
High number of capillaries
o How many are open at any given moment in time (it is
perfectly normal not to be using all your lungs at rest)
o Much less sympathetic tone/vasocontricting forces
What is a major stimulus that causes an increase in
pulmonary vascular resistance?
• A. Activation of alpha-adrenergic receptors
• B. Inhibition of nicotinic receptors on the
vasculature.
• C. The presence of hypoxia in a region of the lung.
• D. An increase in sympathetic activation of the
adrenal medulla.
• C. The presence of hypoxia in a region of the lung.
What is the major role of the vasoconstriction
produced by hypoxia?
• A. Direct the air to the parts of the lung getting the
most blood.
• B. Control the pulmonary blood pressure at normal
levels.
• C. Maintain blood flow to deliver oxygen to the
bronchi
• D. Increase blood flow to areas of the lung with
good oxygenation.
Increase blood flow to areas of the lung with
good oxygenation.
What happens to PVR during exercise
PVR drops as more pulmonary capillaries open up to accommodate the increased cardiac output.
What else does pulmonary vascular resistance depend on?
Also depends on lung volume
• At low or very high lung volumes, the resistance
increases a little because the stretch of the tissue
compresses the capillaries.
Normal Value of PVR versus systemic resistance
Low-PVR
Moderate-systemic
Major constrictor for PVR versus systemic resistance
Hypoxia-PVR
Sympathetics for systemic
Value of PVR and systemic resistance during exercise
both decrease
Major control of PVR versus systemic
PVR-local
systemic resistance-ANS
regional blood flow to lungs-base
At the base of the lung, the blood pressure is high
because we are below the level of the heart.
• The alveoli are smaller (take that as a fact right now).
• The blood flow is greater than in other regions of the
lung
regional blood flow to lungs-apex
At the apex of the lung, the blood pressure is reduced
because it is slightly above the level of the heart.
• However, the alveoli are somewhat expanded (take
that as a fact right now).
• The blood flow is less.
summary of regional blood flow
Apex: high alveolar pressure, low blood pressure: Little blood
o Middle regions: Normal pressures on both sides: Normal blood
o Base: Relatively low alveolar pressure, relatively high blood pressure: Lots
of blood.
Nitric oxide- where is it made and what does it do
Nitric Oxide –
o Made by the endothelium
o Causes smooth muscle relaxation and vasodilation
o Significant role in normal pulmonary blood flow
Endothelin 1-where is it made and what does it do
Endothelin 1
o Also made in lungs
o Vasoconstrictor
o Seems to be a player under pathologic conditions – not under normal conditions
thromboxane a2
Treat it the same as endothelin 1
