Overview
- ~15.0 g/dL hemoglobin in blood
- most oxygen in blood is attached to hemoglobin
- > 5.0 g/dL deoxyhemoglobin in blood → cyanosis
- ↓ hemoglobin → ↓ O2 content
- ↓ hemoglobin does not change O2 saturation, arterial PO2
- chronic lung disease → ↓ arterial PO2
- physiologic shunt → ↓ O2 extraction ratio
- chronic lung disease → ↓ arterial PO2
- 1.0 g hemoglobin can bind 1.34 mL O2
- O2 binding capacity
- = (15.0 g hemoglobin / dL blood) x (1.34 mL O2 / 1.0 g hemoglobin) = 20.1 mL O2 / dL
- O2 content = (O2 binding capacity) x (% saturation) + dissolved O2
- dissolved oxygen can usually be ignored because it is multiplied by 0.003 to correct for units (mL O2 / mmHg / dL), and becomes negligible
- O2 delivery = (cardiac output) x (O2 content)