11: Pulmonary Blood Flow And Ventilation Flashcards
PaO2 in arteries in systemic vs pulmonary circulation
Pulmonary PaO2: 40 mmHg
Systemic PaO2: 100 mmHg
Pulmonary vs systemic circulation’s response to hypoxia
Pulmonary: vasoconstriction
Systemic: vasodilate
Purpose of hypoxic vasoconstriction in lungs
Directs blood to areas of the lungs with better oxygenation
Mechanism of hypoxic vasoconstriction
Myogenic - SM vasoconstriction without innervation
Mechanism of hypoxia leading to SM contraction
- Hypoxia -> decreased NADH (energy in general)
- Low NADH -> decreases leak channels -> less K leaves cell -> depol occurs
- Depol causes increased L-type Ca channels -> SM contraction
Bronchial capillaries (extra-alveolar caps)
Deliver O2 and CO2 to the tissue of the lungs
Two paths for bronchial capillaries to return to the heart
- Flow into azygos vein and other nearby veins -> RV
2. Flow into pulmonary veins -> creates a venous admixture
Three things that cause decreases pulmonary vascular resistance in COPD
- Gas trapping
- Decreased surface area
- Hypoxic vasoconstriction
Three big chemical modulators of pulmonary blood flow
- NO
- Endothelin 1
- Thromboxane A2
What makes NO and what does it cause?
Made by endothelium -> causes SM relaxation and vasodilation
Endothelin 1 and thromboxane 2: where they’re made and the function
Made in lungs -> vasoconstrction in pathological conditions
What does ACE inactivate?
Bradykinin
ACE inhibitors side affect and why
Can cause a cough bc of an accumulation of bradykinin
What type of metabolism do the lungs play a role in? What are examples of this?
Metabolism of arachidonic acid metabolites - leukotrienes, prostaglandins E2 and FA, thromboxane a2
What is the alveolar gas equation used to calculate?
What inspired O2 is needed to produce a desired alveolar O2 level
FiO2
Fraction of inspired O2, is 21% unless otherwise specified
What does an increase in A-a O2 gradient indicate?
Diffusion impairment in the alveoli
What does it mean if the A-a gradient is normal, but PaO2 and PAO2 are both low
There is a problem outside of the lungs (ex: the pt may be hypoventilating)
Intra pleural pressure in lung’s apex vs base
Apex: more negative pressure bc of less intrapleural fluid (-10 cm H2O)
Base: less negative pressure bc of more intrapleural fluid + the force of gravity (-2 cm H2O)
V/Q ratio in apex vs middle vs base
Apex: V/Q ratio high (PaO2 = 130, PaCO2 = 28)
Middle: V/Q is about 0.8 (nl)
Base: V/Q ratio is low (PaO2 = 89, PaCO2 = 42)
VQ ratio in a space with less alveoli present (ex: in COPD)
High V/Q
Mechanism to minimize differences in V/Q ratios in the different zones of the lung
Hypoxic vasoconstrction
