Pulmonary vascular physiology Flashcards
describe pulmonary blood supply
unique dual blood supply
describe pulmonary circulation
from RV
100% CO, involved in gas circulation, huge SA for gas exchange
describe bronchial circulation
2% of LV output
what are the differences between pulmonary and systemic blood vessels
pulmonary v systemic; thin v thick vessel wall minor v significant muscularisation no need v need for redistribution high v low pressure
what is the purpose of systemic blood vessel
deliver O2 to hypoxic tissue
what is the purpose of pulmonary blood vessels
pick up o2 from oxygenated lungs
what are vasodilators in systemic blood vessels
hypoxia
acidosis
CO2
what are vasoconstrictors in systemic blood vessels
oxygen
what are vasodilators in pulmonary blood vessels
oxygen
what are vasoconstrictors in pulmonary blood vessels
hypoxia
acidosis
what does oxygen do in pulmonary vessels
vasodilates
what does oxygen do in systemic blood vessels
vasoconstricts
what is the equation for pressure across a circuit
CO x resistance
what is an equation for pressure across pulmonary circulation
= mPAP - LA pressure x PVR
what is alveolar recruitment
pulmonary capillary response to increased pulmonary artery pressure
occurs as a consequence of exercise
- compressed pathways open
what do recruitment and distension do
reduce resistance
what is the difference between recruitment and distension
recruitment opens compressed arteries/ cpilaries, distention stretches arteries/ capillaries that are already open
describe type 1 respiratory failure
pO2 < 8kPa
pCO2 < 6kPa
- can’t get O2 in
describe type II respiratory failure
pO2 < 8kPa
pCO2 > 6kPa
- can’t get O2 in or CO2 out = ventilation problem
what is hypoxia
deficiency of O2 at tissue level - low pO2
what is hypoxemia
arterial pO2 reduced
what is hypercapnia
too much CO2 at tissue level; high pCO2
what detects hypercapnia and what is the consequence
chemoreceptors
alters HR and BR
can cause respiratory acidosis
types of hypoxia
hypoxaemia/ hypoxic hypoxia
anaemia/ CO hypoxia
ischemia/ stagnant hypoxia
histotoxic hypoxia
how to remember types of hypoxia
HASH
what is the definition of hypoxic hypoxia
decreased oxygen tension
what is the definition of anaemic hypoxia
decreased carrying capacity
what is the definition of stagnant hypoxia
decreased perfusion
what is the definition of histotoxic hypoxia
cellular hypoxia
causes of hypoxia
hypoventilation
diffusion impairment
shunting
V/q mismatch
what is the effect of hypoxia in the lungs
vasoconstriction
what can hypoventilation cause
type II respiratory failure due to increased arterial pCO2
what can cause hypoventilation
muscular weakness, obesity, loss of respiratory drive
what is diffusion impairment in regards to hypoxia
failure of blood pO2 and alveolar pO2 to equilibrate
what is a cause of gaseous diffusion impairment
pulmonary oedema
what is a cause of membrane diffusion impairment
interstitial fibrosis
what is a cause of blood diffusion impairment
anaemia
what are the 3 types of diffusion impairment
gaseous, membrane, blood
define shunting
blood goes through a completely non-ventilated area
causes of shunting (lungs)
intrapulmonary deficit; e.g. asthma, pneumonia, pulmonary oedema, PAVM, complete lobar collapse
what is an intrapulmonary deficit
mixed venous blood perfuses unventilated area
what is PAVM
pulmonary arteriovenous malformation (R to L shunt between PA and vein)
what can shunting lead to
V/Q mismatch
can you have V/Q mismatch without shunting
yes; if cause is arterial e.g. emboli
what is the most common cause of V/Q mismatch
discrepancies in amount of air reaching alveoli v amount of blood arriving in capillaries
describe V/Q mismatch
total ventilation and perfusion is normal but well ventilated regions can’t compensate for poorly ventilated regions
causes of V/Q mismatch
physiological, pulmonary emboli, asthma, pneumonia, pulmonary oedema
what is the effect of V/Q mismatch
pO2 decreases in systemic arterial blood
what happens if O2 in alveoli decreases
hypoxic vasoconstriction, perfusion decreases so blood diverted away from poorly ventilated areas towards well-ventilated areas
what does a decrease in CO2 do to bronchioles
constriction so ventilation decreases
what does an increase in co2 do to bronchioles
dilation so ventilation increases
what does hypoxia do in the lungs
vasoconstriction
hypoxaemia causes
hypoventilation diffusion impairment shunting V/ Q mismatch (same as hypoxia)
what is the difference between hypoxia and hypoxaemia
deficiency of oxygen at tissue level (hypoxia) v arterial level (hypoxaemia)
what are the 2 forms Hb can exist in
Hb = deoxyhaemoglobin HbO2 = oxyhaemoglobin
describe the shape of an OD curve
non-linear, sigmoid
what is an equation for the combination of Hb with oxygen
O2 + Hb ⇆ HbO2
explain the shape of an OD curve
O2 binds to each subunit sequentially
where is O2 given up from Hb
areas of low pO2 i.e. metabolically active tissue
what is the effect of increased pH on OD curve
shifts to left - more affinity for O2
what is the effect of decreased pH on OD curve
shifts to right - less affinity for O2 -gives up more
what is the effect of increased temperature on OD curve
shifts to right - less affinity for O2 - gives up more
what is the effect of decreased temperature on OD curve
shifts to left - more affinity for O2
what is the effect of increased CO2 in OD curve
shifts to right - less affinity for O2 - gives up more
what is the effect of decreased CO2 on OD curve
shift to left - more affinity for O2
what is the affinity of CO v O2 for Hb and what is the effect
200 times greater affinity
CO irreversibly binds so reduces amount of O2 that can combine with Hb
Alters Hb molecule so has more affinity for O2 so OD shifts right so decreased unloading in tissue
what is 2-3 diphosphoglycerate
created in erythrocytes during glycolysis
what is the effect of high levels of 2-3 diphosphoglycerate on OD curves
shifts them to the right
what is the name of the molecule made by erythrocytes during glycolysis that shifts OD curve to right in high levels
2-3 diphosphoglycerate
