Study of early warning for desaturation provided by Oxygen Reserve Index in obese patients.

Acute hemoglobin desaturation can reflect rapidly decreasing PaO. Pulse oximetry saturation (SpO) facilitates hypoxia detection but may not significantly decrease until PaO < 80 mmHg. The Oxygen Reserve Index (ORI) is a unitless index that correlates with moderately hyperoxic PaO.