Pulmonary Blood flow Flashcards
Alveolar capillaries
-Are involved in the exchange of?
- Alveolar capillaries are involved in the exchange of O2 and CO2 between blood and air
- Millions of alveolar capillaries make it so the alveoli are effectively a sheet of capillaries
Extra-alveolar capillaries
-Arise from?
The left ventricle
Extra-alveolar capillaries-function?
- Function as normal systemic capillaries
- Deliver O2 and CO2 to the tissue of the lungs
- Provide nutrients/remove waste from lung tissue
Extra-alveolar capillaries-Return to the heart in the pulmonary veins (venous admixture)
-Effect on PaO2 of the arterial blood? PaCO2?
- Reduces the PaO2 of the arterial blood by a few mmHg
- Increases the PaCO2 to a small degree
Alveolar and Extra-alveolar capillaries return to the heart via?
Pulmonary veins
Alveolar capillary
- PaO2? - PaCO2? - How do these levels compare to those extra-alveolar capillaries?
- Low PaO2
- High PaCO2
- These levels are switched in extra-alveolar capillaries
After the alveolar capillaries return via the pulmonary vein, what are the blood gases?
High PaO2, Low PaCO2
After the extra-alveolar capillaries return via the pulmonary vein, what are the blood gases?
Low PaO2, High PaCO2
Pulmonary vascular resistance
-Important reminder- BP=?
BP = CO x TPR
This equation holds true in the lung as well, but substitute in pulmonary vascular resistance (PVR) for TPR
PBP = CO x PVR
Normal pulmonary blood pressure?
Normal cardiac output?
- Normal PBP is 25/15 (MAP = 18)
- Cardiac output is 4 L/min
Systemic side
- Normal systemic mean arterial pressure?
- Normal cardiac output?
- Systemic MAP = 90 mmHg
- Cardiac output = 4 L/min
Ratio of PVR to systemic?
1/4
Pulmonary vascular resistance is determined by?
- High number of capillaries
- How many capillaries are open at any given moment in time (it is perfectly normal not to be using all your lungs at rest)
- Much less sympathetic tone/vasoconstricting forces
- Lung volume
What is the major role of the vasoconstriction produced by hypoxia?
Increase blood flow to areas of the lung with good oxygenation
Pulmonary Vascular Resistance
- How many capillaries are open at any given moment in time (it is perfectly normal not to be using all your lungs at rest)
- How does exercise affect PVR?
During exercise, PVR drops as more pulmonary capillaries open up to accommodate the increased cardiac output
PVR also depends on lung volume
-What happens to resistance at low or very high lung volumes?
The PVR increases a little because the stretch of the tissue compresses the capillaries
PVR-normal value?
LOW
PVR-major constrictor?
Hypoxia
PVR-Change with exercise?
Decreases
PVR-Major control?
Local
Systemic resistance-normal value?
Moderate
Systemic resistance-major constrictor?
Sympathetics
Systemic resistance-change with exercise?
Decrease
Systemic resistance-Major control?
ANS
Regional blood flow in the lungs?
- As we already know, gravity works on the blood in our bodies- when we stand, the hydrostatic pressure in our legs is increased compared to the level of the heart or in the brain
- The same is true in the lungs
Regional blood flow in the lungs
-Zone 1/apex?
- PA > Pa > PV
- 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 as fact for right now)
- The blood flow is less
Regional blood flow in the lungs
-Zone 2/pulmonary artery/vein?
- Pa > PA > PV
- In the middle regions of the lung, the blood pressure is a little higher because we are at the level of the heart
- The alveoli are average size (take as fact right now)
- The blood flow is “normal’
Regional blood flow in the lungs
-Zone 3?
- Pa > PV > PA
- 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 as fact right now)
- The blood flow is greater than in other regions of the lung
Regional blood flow (short and sweet)
-Apex?
High alveolar pressure, low blood pressure: little blood
Regional blood flow (short and sweet)
-Middle regions?
Normal pressures on both sides: Normal blood
Regional blood flow (short and sweet)
-Base?
Relatively low alveolar pressure, relatively high blood pressure: lots of blood
Chemical Modulators of pulmonary blood flow
- Nitric oxide
- produced by?
- Causes what to happen?
- Significant role in?
- Produced by the endothelium
- Causes smooth muscle relaxation and vasodilation
- Significant role in normal pulmonary blood flow
Endothelin 1
- Produced in?
- Causes what to happen?
- Seems to have a role under what type of conditions?
- Produced in the lungs
- Causes vasoconstriction
- Seems to be a player under pathologic (not normal) conditions
Thromboxane A2
-Treat it the same as endothelin 1-can be found under certain pathologic conditions
lalaedsnfd
Describe the mechanisms by which the alveoli are kept “dry”
The lymphatics! (filter out fluid)
Describe the role of the lung in the production of angiotensin 2
Has angiotensin converting enzyme (ACE)
-converts angiotensin 1 to angiotensin 2
Describe the role of the lung in the metabolism of bradykinin?
ACE (angiotensin converting enzyme) inactivates bradykinin
Describe the role of the lung in the production/metabolism of arachidonic acid metabolites
Leukotrienes and prostaglandins are produced by immune system activation in the lungs
Prostaglandin E2, F2a, and leukotrienes are almost completely removed from the circulation in the lungs
Alveolar Capillaries
-Arise from?
the right ventricle
