Extracorporeal membrane oxygenation (ECMO) circuit priming procedures are crucial for removing air bubbles and the albumin in priming solution is thought to create a protective layer against blood exposure and protein binding.¹ However, the binding profile to the ECMO circuit after priming remains unexplored. This study aims to characterize proteins bound to the ECMO circuit after priming, and the corresponding priming solutions using data-dependent acquisition mass spectrometry (DDA-MS).