What is the primary purpose of adequate preoxygenation during EEI in obese patients?

• A. To fill the lungs with oxygen and extend safe apnea time.
• B. To oxygenate only after intubation.
• C. To test oxygen delivery systems.
• D. To achieve hyperoxia for long-term ventilation.

Answer: (A)

Maximizing the oxygen reserve in the lungs before apnea is the key idea. In obese patients, functional residual capacity is reduced and oxygen is consumed quickly, so desaturation happens fast once ventilation stops during laryngoscopy. Adequate preoxygenation fills the lungs with oxygen, displacing nitrogen, and creates a larger oxygen reservoir. This extends the safe apnea time—the window from the onset of apnea to critical desaturation—giving the clinician more time to secure the airway without hypoxemia. Techniques like delivering 100% oxygen with a tight mask seal (often for several minutes) help achieve this, and alternative methods such as NIV or high-flow oxygen can aid denitrogenation if needed. The other options aren’t the primary aim: preoxygenation is performed before intubation, not after; it isn’t primarily about testing delivery systems; and hyperoxia for long-term ventilation isn’t the goal of this maneuver.