At what oxygen saturation percentage does clinically significant hypoxia typically begin?

Oxygen saturation (SpO2) is measured by pulse oximetry. Normal SpO2 is 95-100%. Clinically significant hypoxia is generally defined as SpO2 below 90% (equivalent to PaO2 below approximately 60 mmHg on the oxyhemoglobin dissociation curve). At this point, there is a steep decline in oxygen delivery to tissues. In the dental office, SpO2 below 90% requires immediate intervention (supplemental oxygen, repositioning, reversal of sedation if applicable, and emergency medical services if not rapidly corrected). An SpO2 of 85% represents moderate-to-severe hypoxia with high risk of organ damage.