ECMO Physiology & Gas Exchange Flashcards
7 cards from real CES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 ECMO Physiology & Gas Exchange flashcards as text
The 'Harlequin' (North-South) syndrome in femoral VA-ECMO occurs when:
Answer: The upper body receives desaturated native cardiac output while the lower body receives oxygenated ECMO blood
When the native heart partially recovers and ejects desaturated blood, the coronary arteries and brain may receive poorly oxygenated blood while the ECMO return site (femoral artery) perfuses the lower body with well-oxygenated blood.
In VV-ECMO, which factor most directly determines the patient's cardiac output?
Answer: The patient's own intrinsic cardiac function and vascular tone
VV-ECMO does not provide direct cardiac support; the patient's native cardiac output depends entirely on their own myocardial function and loading conditions.
A progressively decreasing pre-membrane to post-membrane PO2 gradient in the oxygenator over several days suggests:
Answer: Progressive membrane lung failure or clotting reducing gas transfer
A falling transmembrane PO2 gradient indicates the oxygenator is becoming less efficient, often due to fibrin/thrombus deposition reducing the effective gas-exchange surface.
In ECMO, carbon dioxide clearance is most directly controlled by adjusting:
Answer: Sweep gas flow rate
CO2 removal is highly sensitive to sweep gas flow rate; increasing sweep gas increases the CO2 gradient across the membrane, enhancing clearance.
Transmembrane pressure (TMP) across the ECMO oxygenator is monitored primarily to detect:
Answer: Clot formation or membrane failure increasing resistance within the oxygenator
A rising TMP indicates increased resistance across the oxygenator, often due to thrombus formation, signaling the need for oxygenator replacement.
In VA-ECMO, the presence of a pulsatile arterial waveform on the arterial line monitoring indicates:
Answer: Residual or recovering native cardiac contractility
Pulsatility on the arterial waveform reflects the native heart ejecting blood; loss of pulsatility at high ECMO flows indicates full cardiac bypass.
The oxygen transfer capacity of an ECMO membrane oxygenator is most directly influenced by:
Answer: Blood flow rate through the oxygenator
Higher blood flow through the oxygenator increases oxygen transfer up to the membrane's rated capacity; inadequate flow limits contact time and gas exchange.