The pillow doesn't have anything to do with the nitrogen washout. That is for obtaining a "sniffing" position that aligns the oral, pharyngeal, and laryngeal axis in an anatomically optimal manner to ease intubation. Whether you leave the pillow or not is strictly a preference of the endoscopist. Nitrogen washout, also referred to as pre-oxygenation or denitrogenation, is for maximizing the time you have to intubate. As you know, the air you breathe is 21% O2 and 78-79% Nitrogen, 1% other gases. With that being said, at the end of a normal expiration, each person still has more air they can forcefully expire.........this is the expiratory reserve volume (avg =1100cc). Even when you have seemingly blown all the air from your lungs, there is still air in there or they would collapse. This is the residual volume (avg=1200cc). These two volumes together = the Functional Residual Capacity (or FRC). The average FRC is all together is about 2300cc or so give or take, depening on the size, sex, and sicknesses of the patient. Out of that 2300cc, at least 78% of it is Nitrogen. The goal of denitrogenation is to make the FRC be 100% O2. This is done with 3-5 minutes of breathing 100% O2 (there HAS to be a good seal.....no entrained room air allowed!) or sometimes people do it with 4 vital capacity breaths of 100% O2. Depending on what book you read, the avg human consumes O2 at a rate of about 250cc/min. If your FRC is 2300cc, then if it was filled with 100% O2, that would give you about (2300/250=) 9 minutes or so before the patient would desaturate. That would be for a healthy person.Now you must understand that "sick" people usually consume O2 at a lot faster pace so you wouldn't have as much time to intubate but just understand that denitrogenation is to buy you time and the above is a detailed explanation as to how it buys you time. I have seen dentritrogenated patients maintain a 100% saturation for what seems like an eternity with absolutely no ventilation at all.