Why we don't skip the three minutes before induction

Before we put anyone to sleep, we spend about three minutes breathing pure oxygen through a mask. From outside it looks like nothing is happening.

Lung air is mostly nitrogen. Those three minutes wash most of it out and fill the lungs with a reserve of pure oxygen.

If the airway proves difficult and breathing stops, that reserve buys time before oxygen levels start falling. In patients with less reserve, pregnancy, obesity, an emergency, the buffer is smaller, so we take those minutes more seriously, sometimes longer.

It is the same habit as counting instruments before closing: the quiet step that prevents the problem you never want to meet.

General education, not medical advice.