Pulmonary CIrculation Flashcards
Describe the pulmonary circulation.
Largest vascular bed
HIGHLY COMPLIANT vessels
accomodates about the entire Cardiac Output
Pulmonary artery - larger, shorter, more thin walled
Where does the physiological shunt come from?
Bronchial circulation
Describe the Broncial circulation.
1-2% Cardiac output
Empties into the pulmonary veins
Generates the physiological shunt
What happens in Hypoxic pulmonary Vasoconstriction?
Decreased alveolar PO2 causes local vasoconstriction, which leads to blood redistribution to better aerated alveoli.
Defense mechanism to help survive, Unique to lungs
We want to match PO2 to perfusion
What is the common trigger of the HPV response?
Hypoxic Pulmonary Vasoconstriction
Alveolar Hypoxia
Chronically is the main cause of Pulmonary Arterial Hypertension
What is the effect of gravity on Pulmonary blood flow?
blood flow is greater at the base.
Pulmonary circ is a low pressure/low resistance system
Are pulmonary capillaries leaky to protein molecules?
YES
Are pulmonary capillaries low pressure?
YES
What are the factors that determine the pulmonary capillary flow?
Intravascular Hydrostatic pressue, IV oncotic pressue, Capillary permeability, Interstitial Hydrostatic pressue, IS oncotic pressure, lymphatic drainage, alveolar membrane permeability.
What is the normal value for the Ventilation/Perfusion ratio:
.8
Is the ventilation higher/lower in the apex compared to the base of the lung?
Lower
Is t the perfusion higher/lower in teh apex compared to the base of the lung?
Lower
Is the Ventilation/Perfusion ratio higher or lower in the apex as compared to the base?
Higher.
The Perfusion fall faster than the ventilation
Therefor the ratio increases while both values decrease
What is the V/Q ratio in a shunt?
0
What is the V/Q ratio in dead space?
infinity
alveolar gas has the same composition as humidified inspired air
ex: pulmonary embolism
