Circuit Components and Management Flashcards
7 cards from real ECMO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Circuit Components and Management flashcards as text
What is the function of the bladder (reservoir) in a gravity-siphon ECMO circuit?
Answer: To buffer venous return and trigger servo-regulation if flow drops
The venous bladder acts as a reservoir that collapses when venous return is inadequate, triggering servo-regulation to reduce pump speed and prevent suction injury.
Polymethylpentene (PMP) hollow fiber oxygenators have largely replaced silicone membrane oxygenators in ECMO because PMP offers:
Answer: Lower resistance to blood flow and reduced plasma leakage
PMP fibers are true diffusion membranes that minimize plasma leakage (weeping) while providing low resistance and efficient gas exchange.
During ECMO, a sudden rise in the pre-membrane pressure with a normal post-membrane pressure indicates:
Answer: Clot formation within the oxygenator fiber bundle
A rising gradient between pre- and post-membrane pressures signals increasing resistance within the oxygenator, most commonly due to clot accumulation in the fiber bundle.
What is the typical target activated clotting time (ACT) range during standard ECMO anticoagulation?
Answer: 180–220 seconds
Most ECMO centers target an ACT of 180–220 seconds to balance thrombosis prevention in the circuit against bleeding risk in the patient.
The 'north-south syndrome' in VA-ECMO via femoral cannulation describes:
Answer: Differential hypoxia where upper body receives poorly oxygenated native cardiac output while lower body receives well-oxygenated ECMO flow
When the recovering heart ejects poorly oxygenated blood, a mixing zone forms in the aorta creating a differential: hypoxic upper body (brain, coronaries) versus oxygenated lower body from ECMO.
Which intervention is most appropriate for managing harlequin syndrome in VA-ECMO?
Answer: Add a second venous drainage cannula to convert to VAV configuration or place the return cannula in the right subclavian/axillary artery
Converting to a VAV configuration or using an upper-body arterial return ensures oxygenated blood reaches the coronary and cerebral circulations despite poor native cardiac function.
Membrane lung 'failure' is best identified by which combination of findings?
Answer: Elevated transmembrane pressure gradient AND deteriorating post-membrane blood gas PO2
Oxygenator failure manifests as increasing resistance (elevated pressure gradient) alongside reduced gas exchange efficiency detected by post-membrane blood gas analysis.