Oxygenation

The exam rarely asks for a definition; it hands you a scenario and makes you rank assessments or interventions by ABCs. The “tell” is a falling saturation paired with a symptom: dropping SpO2 with restlessness, anxiety, or confusion (the early signs of hypoxia) means act, don’t just chart. The reasoning the keyed answer hinges on is that oxygen delivery (DO2) = cardiac output × arterial oxygen content, so the right move targets the limiting factor — secure the airway first, then improve gas exchange (high-Fowler’s, suction, supplemental O2), then support circulation.

The classic trap is a falsely reassuring SpO2 despite real distress. Pulse oximetry reads saturation, not oxygen content, so it stays near-normal in carbon monoxide poisoning — CO binds hemoglobin ~200–250× tighter than O2, and the oximeter mistakes carboxyhemoglobin for oxyhemoglobin — and in severe anemia, where fewer hemoglobin molecules mean low delivery at a normal percentage. The keyed answer there is co-oximetry or an ABG, not “continue monitoring.” Don’t conflate oxygenation with perfusion (the circulatory leg) or hypoxia (the tissue-level deficit); untreated, the chain ends in anaerobic metabolism and acidosis.