Medical Emergencies · single question
At approximately what peripheral oxygen saturation (SpO2) is a patient generally considered hypoxic and in need of intervention?
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Correct answer: A. 85%
- A. CORRECT. Normal SpO2 is roughly 95–100%. Values below about 90% define hypoxemia, and the commonly cited dental/clinical action threshold is around 85–90%, where the oxyhaemoglobin dissociation curve turns steeply downward and small further drops in PaO2 cause large drops in saturation. Of the choices offered, 85% is the recognised hypoxia threshold requiring supplemental oxygen and airway assessment.
- B. 65% represents critical hypoxia with imminent organ injury. Again far beyond the threshold being asked for.
- C. 75% is severe, life-threatening hypoxia — well past the point at which you should already have intervened. It is not the threshold at which hypoxia begins.
- D. 95% is the LOWER end of NORMAL, not hypoxia. A patient at 95% needs no emergency intervention.
Note: Remember the steep part of the dissociation curve: below ~90% saturation, tiny PaO2 changes cause large SpO2 falls. Act early.
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