Time sparing methods of Preoxygenation described is-

Preoxygenation before anesthetic induction and tracheal intubation is a widely accepted maneuver, designed to increase the body oxygen stores and thereby delay the onset of aerial hemoglobin desaturation during apnea. Because difficulties with ventilation and intubation are unpredictable, the need for preoxygenation is desirable in all patients. During emergence from anesthesia, residual effects of anesthetics and inadequate reversal of neuromuscular blockade can lead to hypoventilation, hypoxemia, and loss of airway patency. In accordance, routine preoxygenation before the tracheal extubation has also been recommended. time sparing method is to ask patient to take 4 full vital capacity breaths.