Use the oxyhemoglobin dissociation curve from your notes to answer this question. What is the percentage unloading of oxygen from oxyhemoglobin if systemic arterial PO₂ is 80 mmHg and systemic venous PO₂ is 20 mmHg?
1) about 65
2) about 45
3) about 60 mm Hg
4) 106 mmHg
