oxygendelivery

Oxygendelivery, also written as oxygendelivery in some texts, refers to the amount of oxygen transported to body tissues per minute. In physiology and clinical practice, it is denoted DO2 and is determined by cardiac output and arterial oxygen content.

DO2 is commonly calculated as DO2 = CO × CaO2, where CO is cardiac output. Arterial oxygen content CaO2 combines the oxygen bound to hemoglobin and the dissolved oxygen in plasma: CaO2 = (Hb × 1.34 × SaO2) + (PaO2 × 0.003). Here Hb represents hemoglobin concentration, SaO2 is arterial oxygen saturation, and PaO2 is the arterial partial pressure of oxygen. The constants 1.34 and 0.003 reflect the amount of oxygen carried per gram of Hb and the solubility of oxygen in plasma, respectively.

Physiologically, oxygendelivery must meet tissue oxygen demand, known as VO2. The Fick principle describes this balance: VO2 = DO2 × (arterial–venous O2 content difference). If DO2 falls below VO2, tissues experience hypoxia unless compensatory mechanisms increase extraction or utilization is reduced. Factors influencing DO2 include heart rate, stroke volume, anemia (lower Hb), hypoxemia (reduced SaO2 or PaO2), and conditions affecting circulation or autonomic regulation.

Clinically, DO2 is used to assess adequacy of oxygen delivery, particularly in critically ill patients. Low DO2 can result from reduced cardiac output, severe anemia, or impaired pulmonary oxygenation. Management aims to optimize DO2 by increasing oxygen availability and delivery: supplemental oxygen or noninvasive/mechanical ventilation to raise SaO2/PaO2, transfusion in anemia, fluids and vasopressors or inotropes to improve cardiac output, and strategies to improve microcirculatory perfusion. Monitoring includes hemoglobin concentration, arterial blood gases, pulse oximetry, and, when available, estimates of DO2 and VO2 to guide therapy.