The effect of excessive gas to blood ratios in an ECMO oxygenator

Michael Shaw; Nigel Cross; Rebecca Richardson; Richard Crook; Timothy Thirulchelvam; Richard W Issitt

doi:10.1177/02676591241256089

The effect of excessive gas to blood ratios in an ECMO oxygenator

Perfusion. 2024 May 23:2676591241256089. doi: 10.1177/02676591241256089. Online ahead of print.

Authors

Michael Shaw¹, Nigel Cross¹, Rebecca Richardson¹, Richard Crook¹, Timothy Thirulchelvam^{2

3}, Richard W Issitt^{1

3}

Affiliations

¹ Perfusion Department, Great Ormond Street Hospital for Children, London, UK.
² Cardiac Intensive Care Department, Great Ormond Street Hospital, London, UK.
³ Centre for Heart Failure, Transplantation and Extracorporeal Support, Research Department of Children's Cardiovascular Disease, UCL Institute of Cardiovascular Science, London, UK.

PMID: 38783478
DOI: 10.1177/02676591241256089

Abstract

Introduction: Oxygenators for paediatric Extracorporeal Membrane Oxygenation (ECMO) are required to operate over a wide range of flow rates, in a patient group ranging from neonates through to fully grown adolescents. ECMO oxygenators typically have a manufacturer's stated maximum gas: blood flow rate (GBFR) ratio of 2:1, however, many patients require greater ratios than this for adequate CO₂ removal. Mismatches in GBFR in theory could result in high gas phase pressures. These increased pressures in theory could cause the formation of gross gaseous microemboli (GME) placing the child at higher risk of neurological injury.

Methods: We evaluated 6 paediatric and 6 adult A.L.ONE™ ECMO oxygenators and assessed their gas phase pressures and GME release, in an ex vivo setting, in GBFR ratios up to greater than 2, across a range of gas flow (1L - 10 L/min) rates with a fraction of inspired oxygen (F_iO₂) content of 50% and 100%.

Results: There were no increases above 10 mmHg observed in gas phase pressures in GBFR >= 2:1 in either adult or paediatric oxygenators. Laboratory examination of GME activity demonstrated a small increase in post-membrane GME release over the study period. GME release was unaffected by F_iO₂ setting or gas flow rate, with a maximum volume of < 6 µL in both paediatric and adult oxygenators.

Conclusions: In an ex vivo setting, increasing GBFR above 2:1 in a paediatric oxygenator, and to a GBFR of 2:1 in an adult oxygenator did not significantly increase gas phase pressures, and no oxygenator membrane rupture was observed. There were no associations between gas flow rates and GME production.

Keywords: extracorporeal membrane oxygenation; gaseous microemboli; oxygenator; paediatrics; perfusion.