What is normal oxygen delivery and what constitutes critical oxygen delivery?

Normal DO2 is approximately 900–1100 mL/min (or 520–570 mL/min/m² indexed). Critical DO2 — the threshold below which VO2 becomes supply-dependent — is approximately 300–330 mL/min/m². Below this threshold, tissue hypoxia occurs regardless of the cause (low cardiac output, severe anemia, or severe hypoxemia). Interventions to increase DO2 include blood transfusion, inotropes, and improving oxygenation.

How does anemia affect oxygen delivery?

Oxygen delivery depends on both cardiac output and arterial oxygen content (CaO2 = Hb × 1.34 × SaO2 + 0.003 × PaO2). Hemoglobin is the dominant determinant of CaO2. A hemoglobin drop from 130 to 70 g/L reduces CaO2 by nearly 50%, halving DO2 if cardiac output is unchanged. The body compensates by increasing cardiac output and oxygen extraction, but critically ill patients often cannot mount adequate compensatory increases.

Oxygen Delivery (DO2) Calculator

Calculate systemic oxygen delivery (DO2 = CO × CaO2 × 10) from cardiac output and arterial oxygen content to assess adequacy of oxygen transport to tissues.

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Frequently Asked Questions

What is normal oxygen delivery and what constitutes critical oxygen delivery?

How does anemia affect oxygen delivery?