Purpose of preoxygenation?

Purpose of preoxygenation?
A. Denitrogenation
B. To increase FRC
C. To decrese residual volume
D. To increase maximum breathing capacity
Dr Yugal chandrakar(DY)
MD Anaesthesia

Ans is A denitrogenation

Preoxygenation turns 21% oxygen in FRC to 100 % …becouse preoxygenation is done with 100% oxygen. So we can call it denitrogenation …

Confusion…it doesn’t mean that we are increasing FRC… becouse FRC is a volume which is fixed. We are just removing nitrogen from FRC by giving 100% oxygen, is called as preoxygenation…