LungWeaner – Hypnoscite

For clinical decision support only. This calculator models VA-ECMO oxygenation using a simplified Fick mixing equation. It assumes a purely respiratory ECMO indication with stable, normal native cardiac function, no significant recirculation, and stable hemoglobin. It does not account for changing lung mechanics during the wean trial, differential hypoxia, or oxygen consumption (VO₂). All values entered remain in your browser only.

1. Patient & Circuit Parameters

Hemoglobin (Hb) Most recent value. Re-enter after any transfusion.

Native cardiac output (CO) From echo or Fick. Should be stable for this model to apply.

L/min

Current ECMO flow Read directly from the circuit flow meter.

L/min

Trial (proposed) ECMO flow The lower flow you are considering for the wean trial.

L/min

Target minimum PaO₂ Suggested safety threshold: 60–80 mmHg.

mmHg

Target SaO₂ (used for minimum ECMO flow calc) Suggested: 90–94%.

2. Remaining Lung/Graft ABG

Sample from the patient arterial line.

PaO₂ (remaining lung/graft)

mmHg

SaO₂ (remaining lung/graft)

3. Post-Oxygenator (ECMO Circuit) ABG

Sampled distal to the membrane oxygenator. Typically PaO₂ 350–500 mmHg and SaO₂ ≈ 100% on full sweep FiO₂.

PaO₂ (post-oxygenator)

mmHg

SaO₂ (post-oxygenator)

Oxygen Content Calculations

Remaining lung/graft O₂ content (C_native)	–	mL O₂/dL
Post-oxygenator O₂ content (C_ECMO)	–	mL O₂/dL
Current mixed arterial O₂ content (C_art)	–	mL O₂/dL
Current mixed arterial SaO₂ (derived)	–	%

Predicted Oxygenation at Trial ECMO Flow

Predicted mixed C_art at trial flow	–	mL O₂/dL
Predicted SaO₂ at trial flow	–	%
Predicted PaO₂ at trial flow	–	mmHg

Minimum ECMO Flow Required

Target O₂ content (from target SaO₂)	–	mL O₂/dL
Minimum ECMO flow (Q_min)	–	L/min

Summary

Current mixed PaO₂ (weighted average)	–	mmHg
ECMO flow as % of total flow	–	%

Safety reminders

Target PaO₂ ≥ 60 mmHg is the absolute minimum; prefer ≥ 70–80 mmHg before committing to a wean.
Wean in 0.5 L/min steps with a repeat ABG after ~15 minutes at each step.
Maintain ECMO flow ≥ 1 L/min to reduce circuit thrombosis risk.
This model assumes remaining lung/graft function does not change as flow is reduced — reassess with each step.
If differential hypoxia is suspected, repeat sampling from the patient arterial line.