What is the primary purpose of preoxygenation before induction of anesthesia?

What is the primary purpose of preoxygenation before induction of anesthesia?

• A. To reduce anesthesia depth.
• B. To denitrogenate the lungs and create an oxygen reservoir to postpone desaturation during apnea.
• C. To measure oxygen saturation.
• D. To wash out CO2.

Answer: (B)

Preoxygenation aims to maximize the oxygen reserve in the lungs by replacing the nitrogen with 100% oxygen. When induction leads to a brief period of apnea, the amount of oxygen stored in the lungs determines how long ventilation can be withheld before desaturation occurs. By denitrogenating the lungs, you raise the alveolar and arterial oxygen tensions, creating a buffer that postpones hypoxemia during the apneic interval. In practice this is achieved by breathing 100% oxygen for several minutes or taking rapid, deep breaths with high FiO2 before induction. This is especially important in patients with limited reserve, such as those with obesity or airway challenges. The other options don’t reflect the primary goal: preoxygenation isn’t about reducing anesthesia depth, measuring oxygen saturation, or washing out CO2.

Preoxygenation aims to maximize the oxygen reserve in the lungs by replacing the nitrogen with 100% oxygen. When induction leads to a brief period of apnea, the amount of oxygen stored in the lungs determines how long ventilation can be withheld before desaturation occurs. By denitrogenating the lungs, you raise the alveolar and arterial oxygen tensions, creating a buffer that postpones hypoxemia during the apneic interval. In practice this is achieved by breathing 100% oxygen for several minutes or taking rapid, deep breaths with high FiO2 before induction. This is especially important in patients with limited reserve, such as those with obesity or airway challenges. The other options don’t reflect the primary goal: preoxygenation isn’t about reducing anesthesia depth, measuring oxygen saturation, or washing out CO2.