Flashcards in PHYS: Pulmonary Blood Flow Deck (22):
Which has a higher pressure, the pulmonary artery or the aorta?
Aorta! PVR is a ninth of systemic vascular resistance
Why is low pulmonary arterial pressure especially important during exercise?
RBCs pass through capillaries slowly in a low pressure system (maximize oxygen exchange because O2 is perfusion limited). During exercise, pressure increases in the pulmonary artery, so RBCs pass through more quickly. However, as pressure increases, the apex of the lung becomes better perfused, which increases the cross sectional area and attenuates the effect that decreased time at the capillary would have on oxygen saturation.
What are the two reasons why blood flow increases from the apex to the base of the lungs?
1) Vascular resistance decreases
2) Pressure drop increases
Increases in pulmonary artery pressure do what to vessels at the base of the lung?
Distends them! (get more blood flow)
Which part of the lung has a higher blood pressure, the apex or the base?
What factors favor fluid flow OUT of capillaries?
1) Capillary hydrostatic pressure
2) Interstitial fluid pressure
3) Osmotic pressure of interstitial fluid proteins
What factors favor fluid flow INTO capillaries?
ONLY the osmotic pressure of plasma proteins
Why do you get edema more commonly at the base of the lungs?
Pressure at the base of the lung is highest, so you would expect hydrostatic pressure to increase over osmotic pressure here (if it happens at all), which leads to pulmonary edema
What happens to vasculature if the Po2 in the alveoli is lowered (hypoxia) OR if the CO2 increases (hypercapnia/acidosis)?
Vessels will constrict in order to shunt blood into better ventilated areas
Hypoxia leading to increased pulmonary vascular resistance can lead to what condition?
chronic pulmonary hypertension
Chronic pulmonary HTN has what effect on the heart?
leads to increased RV load and EDP--> right ventricular hypertrophy--> cor pulmonale (right sided heart failure)
What are the 3 main functions of the lung?
1) increase O2, decrease CO2
2) Filter blood
3) Vasoactive substances (ex. activation of angiotensin)
What is a normal A-a gradient?
What is worse, a higher or lower A-a?
HIGHER A-a gradient indicates hypoxia, because blood with a lower Po2 is in the systemic circulation
Where is the V/Q ratio the highest?
at the APEX of the lung (very well ventilated but poorly perfused)
If you get increased ventilation, the Pao2 will look more like what?
If you get increased flow, the Pao2 will look more like what?
Is V higher at the apex or base?
Is Q higher at the apex or base?
If V and Q are both higher at the base, why is the V/Q ratio higher at the apex?
because blood flow is so much lower at the apex than the base
Which has a higher Po2, the apex or base of the lung?
apex! (also has a lower Pco2)