ECMO DO2 VO2 Ratio Calculator

ECMO DO₂/VO₂ Calculator

Comprehensive oxygen delivery assessment with Impella integration, native CO estimation from echo, and clinical decision support

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ECMO Configuration

ECMO Flow (L/min)

Sweep Gas (L/min)

Circuit FiO₂ (%)

Recirculation (%)

Cannulation

IABP

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Impella / Percutaneous VAD

LV Unloading

Impella Device

Impella Flow (L/min)

P-Level

▶ How does Impella contribute to total flow & DO₂?

Impella + VA-ECMO ("ECPella") — Physiology

VA-ECMO increases LV afterload by returning blood retrograde into the aorta. This can cause LV distension, increased LVEDP/PCWP, pulmonary edema, and LV thrombus. Impella directly unloads the LV by aspirating blood from the LV cavity and ejecting it antegrade into the ascending aorta.

Impella IS the Antegrade Flow

In ECPella, the Impella is the primary mechanism of forward flow through the aortic valve. Blood reaches the LV via pulmonary venous return (bronchial circulation, residual RV output, Thebesian veins). Without Impella, this blood would pool in the LV causing distension. The Impella takes this blood and ejects it into the aorta — this flow contributes to systemic DO₂.

Think of it this way: on VA-ECMO, total systemic flow = ECMO retrograde flow + antegrade aortic flow. The Impella replaces or supplements native cardiac output as the antegrade component. When the native heart has zero ejection, the Impella IS the only forward aortic flow.

Why It's Not Simply "ECMO + Impella + Native CO"

The Impella and native ejection share the same pathway — they both push blood through the aortic valve into the ascending aorta. If you measure LVOT VTI with the Impella running, that VTI already captures the Impella-generated flow. So you should not add Impella flow on top of a native CO measured while Impella is running — that would double-count.

How This Calculator Handles It

When a left-sided Impella is selected, the Native CO field is locked to 0. The Impella flow is used directly as the antegrade component:

Total Flow = ECMO Flow + Impella Flow + IABP augmentation DO₂ = Total Flow × CaO₂ × 10

This prevents any possibility of double-counting. If you measure LVOT VTI with the Impella running, the "Apply →" button routes the result to the Impella flow field (not Native CO), since that VTI reflects Impella-generated forward flow.

When no left Impella is present, Native CO is unlocked and used normally:

Total Flow = ECMO Flow + Native CO + IABP augmentation

Additional Benefits Beyond DO₂

• Maintains pulsatility and coronary perfusion pressure
• Prevents aortic root stasis and aortic valve thrombus
• Decompresses the LV — reduces wall stress, LVEDP, PCWP
• Reduces LV myocardial oxygen demand (MVO₂)
• Facilitates lung recovery by reducing pulmonary congestion

Impella RP (Right-Sided)

Impella RP pumps from IVC/RA → PA, augmenting transpulmonary flow. This increases LV preload, which may increase native CO. The effect is seen indirectly — remeasure LVOT VTI after RP placement and update native CO accordingly.

Max Flows by Device

Impella CPup to 3.5 L/min (14 Fr)

Impella CP Smartup to 4.3 L/min (14 Fr)

Impella 5.0up to 5.0 L/min (21 Fr, surgical)

Impella 5.5up to 5.5 L/min (21 Fr, surgical)

Impella RP / RP Flexup to 4.0 L/min (right-sided)

Clinical Pearl: In ECPella, maximize Impella support (P8–P9) to maximize antegrade flow and LV decompression, then titrate ECMO down as tolerated. Monitor AV opening on echo — if the AV opens only because of Impella, the Impella flow represents the entirety of your antegrade contribution to DO₂. When weaning: reduce ECMO first, Impella last.

Measuring Native CO: When a left-sided Impella is active, the Native CO field is automatically locked to prevent double-counting. The Impella flow IS the antegrade aortic flow. If you measure LVOT VTI with Impella running, the "Apply →" button in the VTI calculator will update the Impella flow field (not Native CO), since that VTI reflects Impella-generated flow. When no Impella is present, "Apply →" updates Native CO as usual.

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Patient

Weight (kg)

Height (cm)

Temp (°C)

Clinical State

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Hemodynamics & Native CO

Native CO (L/min)

Patient Cardiac Output (L/min — required)

MAP (mmHg)

HR (bpm)

CVP (mmHg)

▶ Estimate Native CO from LVOT VTI on Echo

LVOT VTI Method — Step by Step

Native cardiac output can be estimated from TTE or TEE using the LVOT velocity-time integral (VTI).

SV = LVOT CSA × LVOT VTI CO = SV × HR Where: LVOT CSA = π × (LVOT diameter / 2)² = LVOT diameter² × 0.785

Step 1: Measure LVOT Diameter

Parasternal long-axis (PLAX) view, mid-systole, inner edge to inner edge. Typical: 1.8–2.3 cm.

Step 2: Measure LVOT VTI

PW Doppler at LVOT (apical 5-chamber or deep transgastric on TEE). Trace the velocity envelope. Normal: 18–22 cm. On VA-ECMO with severe LV failure, VTI may be <5–10 cm.

Step 3: Calculate

LVOT Diameter (cm)

LVOT VTI (cm)

LVOT CSA—

Stroke Volume—

Native CO (SV × HR)—

Native CI—

Estimated Native CO: —

Interpreting VTI on VA-ECMO

VTI < 5 cmMinimal native ejection

VTI 5–10 cmSome recovery, partial support

VTI 10–15 cmModerate recovery

VTI > 15 cmGood native function, consider weaning

Limitations on ECMO: LVOT VTI may underestimate native CO if the aortic valve doesn't open every beat. A non-opening AV means VTI ≈ 0. Always check for AV opening on M-mode or 2D. PA catheter thermodilution is unreliable on VA-ECMO.

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Laboratory Values

Hemoglobin (g/dL)

SaO₂ / SpO₂ (%)

SvO₂ (%)

Lactate (mmol/L)

PaO₂ (mmHg)

LDH (U/L)

PaCO₂ (mmHg)

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Vasopressors / Organ Function

Optional

Norepinephrine (mcg/kg/min)

Epinephrine (mcg/kg/min)

Vasopressin (U/min)

Dobutamine (mcg/kg/min)

Milrinone (mcg/kg/min)

BUN (mg/dL)

Creatinine (mg/dL)

Platelets (×10³/µL)

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DO₂ / VO₂ Ratio

Enter Data

ECMO — Native — Impella — IABP —

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Oxygen Delivery Breakdown

DO₂

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Critical DO₂

—

Est. VO₂

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O₂ Extraction

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Oxygen Content & Delivery

CaO₂ (Arterial O₂ content)—

CvO₂ (Venous O₂ content)—

Total Effective Flow—

↳ ECMO—

↳ Native CO—

↳ Impella—

↳ IABP augmentation—

DO₂ (O₂ Delivery)—

DO₂ Index (per kg)—

DO₂ Index (per m²)—

Oxygen Consumption & Ratio

Estimated VO₂ (metabolic demand)—

VO₂ via Fick (measured extraction)—

DO₂ / VO₂ Ratio—

O₂ Extraction Ratio—

Critical DO₂ Threshold—

BSA (DuBois)—

ECMO Flow Adequacy

Target (50 mL/kg/min)—

Target (60 mL/kg/min)—

Target (70 mL/kg/min)—

Current % of Optimal—

VIS Score—

Native CO from LVOT VTI

LVOT Diameter—

LVOT CSA—

Stroke Volume—

Native CO (VTI)—

Enter patient data and calculate to see recommendations.

Calculate first to generate scenarios.

Target DO₂/VO₂ Ratio

Max Achievable Flow (L/min)

Max Transfusion Hgb (g/dL)

Required DO₂ to Reach Target

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Enter patient data and calculate first.

Hgb × Flow Nomogram — DO₂/VO₂ Ratio at Each Combination

Calculate patient data first to generate the nomogram.

< 2.0 Critical 2.0–2.4 Borderline 2.4–3.0 Compensated 3.0–4.5 Adequate > 4.5 Optimal Current Target

Recommended Pathways to Target

Pathways will appear after calculation.

Impella & LV Unloading

DeviceNone

Flow—

Max Device Flow—

% of Max—

Primary Role—

Added to Total Flow?—

ECPella Strategy

Select an Impella device to see strategy recommendations.

CaO₂ = (Hb × 1.34 × SaO₂) + (PaO₂ × 0.003) CvO₂ = (Hb × 1.34 × SvO₂) DO₂ = Total Flow × CaO₂ × 10 VO₂ = Total Flow × (CaO₂ − CvO₂) × 10 [Fick] O₂ER = (CaO₂ − CvO₂) / CaO₂ BSA = 0.007184 × H⁰·⁷²⁵ × W⁰·⁴²⁵ [DuBois] ── Native CO from Echo ── LVOT CSA = π × (d/2)² = d² × 0.785 SV = CSA × VTI | CO = SV × HR ── Impella in ECPella ── Left (CP/5.0/5.5): Impella = antegrade flow Native CO locked to 0 (prevents double-count) Total Flow = ECMO + Impella Flow + IABP Right (RP): Augments pulm. flow → ↑ LV preload

Reference Thresholds

Critical DO₂/VO₂≥ 2.0–2.4

Normal DO₂/VO₂4–5 : 1

Critical DO₂3.8–4.5 mL/kg/min

VA-ECMO Flow Target50–70 mL/kg/min

Normal LVOT VTI18–22 cm

Hüfner's constant1.34 mL O₂/g Hb

Key References

Guglin et al. VA-ECMO for Adults. JACC Expert Panel, 2019

Lorusso et al. EACTS/ELSO/STS/AATS Consensus, 2021

Spinelli & Bartlett. Hb–Flow model. ASAIO J 2014

Ronco et al. Critical DO₂. JAMA 1993

Pappalardo et al. ECPella. EuroIntervention 2017

Schrage et al. Impella + VA-ECMO. Eur Heart J 2020

⚠ Clinical Decision Support Tool — Not a Substitute for Clinical Judgment. All calculations are estimates. Always correlate with clinical picture, trends, and multidisciplinary team assessment.

ECMO DO2/VO2 Calculator