2. Pulmonary Blood Flow Flashcards
How does extra-alveolar capillaries return blood to the heart? How does this effect the blood content?
It returns via the pulmonary veins. This slightly reduces the O2 concentration of arterial blood and slightly raises the CO2 concentration.
What is a venous admixture?
The deoxygenated blood from the extra-alveolar capillary that’s added to the pulmonary vein.
What is the equation for pulmonary blood pressure (PBP)?
PBP = CO x PVR
PVR = pulmonary vascular resistance
What determines pulmonary vascular resistance?
The high number of capillaries and how many of them are open (more open with exercise to decrease resistance). Lungs also receive less sympathetic/vasoconstricting forces
How does low or very high lung volumes effect pulmonary vascular resistance?
Increases a little due to stretches that compress the capillaries
What part of the lungs receive the least amount of blood? How does this effect the alveoli?
The apex receives the least. The decrease in blood pressure causes the alveoli to expand due to high alveolar pressure. The opposite is true for the base of the lung.
How does nitric oxide (NO) help regulate pulmonary blood flow?
It is made by the endothelium in response to shear stress, then causes smooth muscle relaxation and vasodilation.
How does endothelin 1 help regulate pulmonary blood flow?
Acts as a vasoconstrictor. More important under pathologic conditions.
How does thromboxane A2 help regulate pulmonary blood flow?
Acts as a vasoconstrictor. More important under pathologic conditions.
What is the intrapleural pressure’s role in filtration?
The negative intrapleural pressure creates a negative hydrostatic pressure favoring filtration of fluid from the capillary into the alveolus.
What aids to remove excess fluid in the capillaries to promote better gas exchange?
Lymphatics
What is ACE’s role with bradykinin?
It inactivates it.
Some people on ACE inhibitors develop cough due to accumulation of bradykinin.
What are the metabolic functions of the lung?
Both leukotrienes and prostaglandins/thomboxane A2 are produced by immune system activation in the lungs.
Prostaglandin E2 and F2alpha are also almost completely removed from the circulation in the lungs, as are the leukotrienes.
