Blood Flow and Metabolism Flashcards
pulmonary artery structure?
little smooth muscle
ensures high compliance
pulmonary pressure?
lower mean 15mmHg
systemic pressure?
high mean 100mmHg
transmural pressure
pressure difference between inside and outside of capillaries
as lung expands
larger vessels expand
alveolar vessels?
subject to changes in alveolar pressure and pressure within in them
extra-alveolar vessels?
subject to changes in lung volume (pull of parenchyma)
also, have smooth muscle
pulmonary vascular resistance
much lower than systemic
decreases with increased pressure**
two reasons for drop in pulmonary vascular resistance with increased pressure?
recruitment and distension**
distension
widening of indiviual capillary segments
when do pulmonary capillaries collapse?
alveolar pressure exceeds capillary pressure
vasodilators?
ACh
isoproterenol
NO
prostacyclins
vasoconstrictors?
serotonin
histamine
NE
vascular resistance = ?
input P - output P / blood flow
PVR increase?
- high and low long volumes
- alveolar hypoxia (vasoconstriction)
pulmonary vascular resistance falls?
with increasing arterial or venous pressure
distribution of blood flow in lung?
more to base of lung
- explained by hydrostatic pressure differences
- base of lung has higher arterial pressure
zone 1 of lung?
may be present
- where the pulmonary arterial pressure falls below alveolar pressure
- causes capillaries to be squished (no flow)
maybe during severe hemorrhage, or positive pressure ventilation
ventilated bu not perfused lung?
alveolar dead space
venous pressure
only has an impact on flow if it exceeds alveolar pressure
aka starling resistor
change in pulmonary resistance with change in lung volume?
high resistance at high and low volume
high - because increased alveolar resistance
-increased alveolar pressure and stretching of capillary wall
low - extra-alveolar vessels are constricted at lower volumes (increasing resistance)
what controls alveolar vasoconstriction?
alveolar PO2
ex/ traveling to high altitude (low PiO2)
increased lung volume?
increased PVR
-lengthening and compression of pulmonary capillaries
decreased lung volume?
decreased PVR
-compression and loss of traction of extra-alveolar vessels
increased pulmonary artery pressure, left atrial pressure, pulmonary blood volume, cardiac output?
decreased PVR
-recruitment and distension
gravity?
decreased PVR
-recruitment and distension (because of hydrostatic effects)
increased interstitial pressure?
increased PVR
-compression of vessels
increased blood viscosity
increased PVR
-increased resistance
positive pressure ventilation?
increased alveolar pressure increases PVR
-compression of alveolar vessels
positive intrapleural pressure increases PVR
-compression of extra-alveolar vessels, decreased in pulmonary blood flow
hypoxic pulmonary vasoconstriction
in arterioles of hypoxic area of lung
-smooth muscle contraction
determined by PO2 of ALVEOLAR GAS
fluid collection in lungs?
first to interstitial
then to alveolar space
determined by starling equation
causes of pulmonary edema?
increased hydrostatic pressure increased capillary permeability reduced lymph drainage decreased interstitial pressure decreased colloid osmotic pressure
nitric oxide?
endothelium-derived factor
relaxes pulmonary vessels and capillaries
norepinephrine?
SNS
vasoconstrictor
endothelins?
constrict pulmonary vessels and capillaries
ACE?
in lung, converts ANG I to ANG II
bradykinin?
inactivated by ACE in lung
serotonin?
inactivated by uptake and storage in lung
prostaglandins E1, E2, F2a?
inactivated in lung
NE?
partially taken up in the lung
increased cardiac output?
pulmonary vascular resistance falls
