Table 1 Inclusion and exclusion criteria

Inclusion

- Patients who were scheduled for elective surgery under general anaesthesia were included.

- Age: one to 8 years old.

- ASA I and II only without mild respiratory diseases.

- Patients with normal cardiorespiratory function.

Exclusion

- Children undergoing dental surgeries in which nasal intubation is needed.

- Patients who suffered from quick drops in oxygen saturation more rapidly than healthy children due to different reasons such as respiratory and pulmonary diseases, asthma, active or recent upper respiratory tract infection, syndromes with cardiopulmonary pathologies, cardiac anomalies, anaemia, depressed respiratory effort, ventilation/perfusion imbalance, obstructive sleep apnoea (OSA), and airway obstruction.

- Patients reported with nasal obstruction.

- Patients with grades of laryngoscopic view (Cormack-Lehane) greater than II, which indicates upper airway obstruction.