“Transonic's ELSA monitor quantitatively measures oxygenator clotting which we implemented with our COVID-19 ECMO patients to improve our bedside decision making in circuit component change-outs." Patrick Weerwind, perfusionist at Maastricht University Hospital

Maintaining appropriate anticoagulation to limit clot burden within the ECMO system while prioritizing patient safety remains an intense balancing act for all ECMO centers. The oxygenator is an essential application of ECLS however clot burden is typically highest in this area. By trending the oxygenator’s blood volume, which decreases as clot increases, the ELSA provides a new way of managing clot burden within the oxygenator.


Utilizing the same technology as Recirculation measurements, the paired flowsensors are placed strategically on the ECMO circuit. The injection of normal saline creates a minimal increase in blood flow that the sensitive arterial flowsensors indicates, marking this as T0. The ELSA determines the time is takes for the saline to travel through the oxygenator, T1. OXBV decreases as clot burden increases.Oxygenator Blood Volume Result Screen from ELSA Monitor

Qb X (T1 – T0) = Volume Measured (mL)

OXBV = Blood Flow (Qb) x Mean Transit Time (MTT)



The OXBV measurement is the only oxygenator clot assessment tool that incorporates the entire oxygenator, bringing valuable information to the bedside. When used in conjunction with other parameters, the ELSA provides new insight to critical care teams when making important decisions regarding oxygenator change-outs. Reducing unplanned emergent change-outs increases patient’s safety and improves multidisciplinary teamwork.