Pulmonary Circulation Flashcards
How do the lungs get blood?
Lung gets blood two ways, 2% of left ventricle output through bronchiole circulation and 100% of the right ventricle output
How does bronchiole circulation work?
What is the pulmonary parenchyma?
Pulmonary parenchyma gets O2 and nutrients from bronchial circulation (supplies all the way down bronchioles
This circulationheats and humidifies air
bronchial arteries supply nerves, pleura, and lymph glands too
Whats the difference between pulmonary vascular resistance and systemic vascular re distance
The two circuits are in series so both get same amount of blood flow and need to stay in pace
RV cannot get ahead of LV as this would cause pulmonary edema
LV cannot get ahead of RV as this would cause peripheral edema
PVR is less than SVR, pulmonary vessels have less smooth muscles which makes them more distensible and subject to extravascular compression, and decreasing their pressure and resistance
There are no highly muscular arteriole in pulmonary circulation
What is anastomoses?
connections between bronchiole and pulmonary circulation, these are not typically open but if either system becomes obstructed and is not getting enough blood flow they will open
How does venous drainage occur in the lungs?
In two ways:
Standard way is it drains into azygous vein and then back into systemic circulation
non-standard way is part of bronchial venous drainage (deoxygenated blood) goes into the pulmonary veins (most oxygenized blood), this is part of a normal anatomic shunt
How does lung volume affect pulmonary blood flow?
What are extra alveolar and alveolar vessels?
The most passive influence on PVR
Two types of vessels, extra alveolar and alveolar (AKA pulmonary capillaries, which are between alveoli)
During inspiration the alveolar grow in size and stretch out the pulmonary capillaries, making the radius smaller
Extra alveolar vessels are not directly exposed to the mechanical stretch but are subject to intrapleural and traction, during inspiration, intrapleural pressure decreases, and transmural pressure increases. Traction on the small vessels (alveolar) by the alveolar septa increases, causes increasing in the diameter of the extra- alveolar vessels and decreasing in the resistance within them.
Both types of vessels move opposite to each other
How does the lung being at TLC and RV effect the extra alveolar and alveolar (pulmonary capillaries) vessels?
At RV, PVR is low in pulmonary capillaries and high in extra alveolar vessels
At TLC, PVR is high in pulmonary capillaries and low in extra alveolar vessels
PVR is lowest at FRC
What is the relationship between PVR and blood flow?
As blood flow increases PVR will decrease
Two theories:
-Distention: taking already open vessels and opening them more, pulmonary vessels are very distensible
-Recruitment: opening vessels that are not already open, this makes more sense as the surface area can be increased and eliminate dead space
- both theories allow for lungs to accommodate for increased blood flow
What are some passive influences that decrease PVR?
Increased PAP, increased LAP, increased pulmonary blood volume, increased CO
-Recruitment and distention
Gravity, body position
-decreases in gravity dependent regions, hydrostatic effects lead to recruitment and distention
What are some passive influences that increase PVR?
Increased lung volume (above FRC)
- lengthening and compression of alveolar vessels
Decreased lung volume
- compression of and less traction on extra alveolar vessels
Increased (more positive) interstitial pressure
- compression of vessels
Increased blood viscosity
- viscosity directly increases resistance
positive-pressure ventilation-SUPER IMPORTANT
-Increased alveolar pressure
—compression and derecruitment of alveolar vessels
Positive intrapleural pressure
—compression of extra alveolar vessels, compression of vena cava decreases pulmonary blood flow and leads to derecruitment
What are some active influences that increase PVR?
stimulation of SNS Noreppinephrine and epinephrine Alpha agonists PGF, PGE, Thromboxane Angiotensin Endothelin Histamine Alveolar hypoxia Alveolar hyperapnia Low pH of mixed venous blood
What are some active influences that decrease PVR?
Stimulation of PNS acetylcholine Beta-adrenergic agonists PGE and Prostacyclin Nitric oxide bradykinin
How does blood flow in the bottom of the lung compare to the top>
Higher intravascular pressure distension and recruitment decreased PVR increased blood flow gravity
If you lay on your left side, more blood will go to left side.
What is the relationship to standing, lying down, and sitting with relation to blood flow?
Standing, most BF in bottom of lung
lying down, more at top
sitting more at bottom
What is the relationship with alveolar pressure (PA) and arterial pressure (Pa)?
If the PA > Pa then there will be no blood flow to that alveoli, the pressure is greater outside the vessel than inside the vessel which would cause these vessels to collapse
