35, 34, 33, 32
Keep every central line lumen closed (stopcock or needle-free valve) in ECMO patients; treat a new hiss from the pump head as air until proven otherwise; do not rely on a post-membrane bubble detector for venous air; never raise pump speed to clear an airlock - clamp.
Open hub vs protected hub; pump speeds
DOI 10.3390/medicina60111883; PMID 39597068; PMC11596159
7 Fr triple-lumen CVC tip 0/1/2 cm from drainage cannula distal or proximal hole with hub open vs closed 3-way stopcock vs clave; separately 1/5/25/50 mL air injected into drainage cannula.
In vitro, blood substitute, VV only, one CVC size, only distal CVC lumen tested, no respiration (authors expect vigorous inspiration to increase entry), fixed CVP, one console; descriptive only, three repeats.
Protected hub (stopcock or clave): no air entry at any speed or distance. Open hub near distal hole: air at 2500, 3500, 4500 rpm with tips touching, 3500 and 4500 only at 1-2 cm; near proximal side hole: 3500 and 4500 rpm at all distances, none at 1500/2500. Pump sound at 1 mL and above = first warning sign. Air reached return-side detector at 1 mL (4500 rpm), 5 mL and 25 mL (3500, 4500). 25 or 50 mL stopped flow completely at every speed; smaller volumes transient flow drop with slow oxygenator venting. Authors: return-side detector inappropriate for monitoring circuit air because membrane retains most air; raising speed after airlock risks forcing air through the membrane, so clamp. Cites (secondary) AE incidence up to 4.6% adults, 4.9% neonates; animal lethal dose 200-300 mL or 3-5 mL/kg.
In vitro venovenous model: Cardiohelp with HLS set, 23 Fr 55 cm multistage drainage and 17 Fr return cannula in latex vessels; 40% glycerol at 36 C; CVP 10 cm H2O; 1500/2500/3500/4500 rpm (1.61/3.15/4.56/5.91 L/min); each experiment x3.