Patients who are under general anaesthesia inevitably encounter apnea between the beginning of anaesthesia induction and successful tracheal intubation. Although the significance of preoxygenation with 100% oxygen has been stressed in airway management because it can denitrogenate the functional residual capacity (FRC) of the lungs and thereby increase the FRC oxygen store and delay the onset of arterial desaturation and hypoxemia, inadequate preoxygenation is a frequent occurrence. The imbalance of carbon dioxide (CO2) and oxygen exchange that occurs during apnoea causes a decrease in alveolar pressure. Apnoeic oxygenation is caused by the subatmospheric negative pressure in the alveoli, which causes a mass flow of gas from the pharynx to the alveoli. Patients who may not be able to be intubated or oxygenated following anaesthesia induction require apnoeic oxygenation, which can extend the safe apnoea time. Extending the safe apnoea time may allow for longer intubation and airway instrumentation. Different groups of people's safe apnoea times can be effectively extended. High-flow nasal oxygen therapy (HFNO) is not practical for complicated intubation emergencies. A modified nasopharyngeal airway can be directly connected to oxygen and monitored end-tidal carbon dioxide (PetCO2) during mechanical ventilation. The use of the modified Naso-Flo monitoring and filtration system is exactly the same as using a traditional nostalgic airway.