10. Capnography Flashcards
EtCO2
[CO2] expired gas
how is EtCO2 measure
exhaled gas analyzer (capnograph)
PaCO2
[CO2] in arteries
(slightly higher than EtCO2)
how is PaCO2 measured
arterial blood gas lab
PaCO2 vs EtCO2
PaCO2 is 3-5 mmHg higher than EtCO2
PaCO2 and EtCO2 normal relationship
proportional
incr PaCO2 = incr EtCO2
when can PaCO2 and EtCO2 be inversely proportional
drop in CO
or
low BP
PaCO2 incr
EtCO2 decr
capnograph
exhaled gas analyzer
capnograph measures
end tidal CO2
end tidal agent concentration
respiratory rate
water trap
can get overfilled w/condensation
weird end tidal readings = time to change or dump out
sample line occluded reading means
time to replace water trap
or
aspirate water with syringe
GA capnography
tubing hooks to anesthesia circuit
MAC capnography
tubing placed inside breathing mask
MAC capnography w/nasal cannula
special cannula w/capnograph line attached
Low CO/ Low BP
incr PaCO2
decr EtCO2
less CO2 taken to alveoli to be exhaled = more CO2 in blood
treatment for hypotension
bolus (20mg) of Ephedrine
EtCO2 is so powerful at telling us
whether or not hypotension is serious enough to compromised perfusion
hypotension accuracy can be verified by
EtCO2
if EtCO2 is low, then likely that BP is also low and tissue perfusion has decreased
low EtCO2 and Low BP indicates
perfusion has decreased
physiologic effects of hypercarbia (hypercapnia)
- respiratory acidosis
- central pulmonary vasoconstriction
- peripheral/cerebral vasodilation
- sympathetic response/catecholamine release
- CO2 narcosis
- possible death
respiratory acidosis
pH decrease
incr CO2
incr acid in body (H+)
decr pH
acidosis can cause
catecholamines dont work
vasopressors dont work
cardiac function depressed
treatment for acidosis
bicarbonate
incr BP
central pulmonary vasoconstriction
incr CO2 = pulmonary vasoconstriction = PVR
do not hyperventilate what type of pts
hypotensive pts
hyperventilation decr CO2
pulmonary vasodialtion
do not hypoventilate what type of pts
hypertensive pts
pts in neurosurgery
pts w/head injury
hypoventilation incr CO2
pulmonary vasoconstriction
peripheral/cerebral vasodilation
decr in SVR
incr CBF / incr ICP
incr CO2 = peripheral/cerebral vasodilation
at high levels CO2 can act as a
sedative
what level does CO2 trigger narcosis/suppress respiratory drive
70mmHg
1 MAC = _____ PaCO2
1 MAC = 200 mmHg PaCO2
what level does CO2 become life threatening?
> 120mmHg