In the preoperative period, age, body weight, height, neck circumference, comorbidities (Charlson comorbidity index), ASA score, Modified mallampati classification, STOP-BANG risk score will be recorded.Intraoperative monitorization data will be recorded.
Following ultrasonographic airway measurements will be performed preoperatively and postoperatively.
A low frequency convex probe will be used for ultrasonography. To achieve a fixed position of the tongue, patients will be placed supine without a pillow, with their head fully tilted back, and asked to hold their tongue loosely, without phonation, with their mouth closed and tongue tips lightly touching the incisors. The probe will be placed under the chin in the median sagittal plane and adjusted to obtain a clear median sagittal tongue view.
Tongue thickness: When the ultrasound probe is placed under the chin on the median sagittal plane, with the mouth closed in the supine position, the tongue is in a natural position and the patient is silent, and the tongue root is displayed on the screen, the maximal vertical diameter from the tongue surface to the submental skin will be measured and recorded as tongue thickness .
Median sagittal tongue cross-sectional area: The sagittal cross-sectional area of the tongue will then be measured by tracing the circumference of the tongue on the ultrasound machine.
Tongue width: The tongue width will then be obtained by measuring the distance between the probe placed transversely under the chin and the furthest points in the middle of the tongue in order to obtain as complete a tongue contour as possible.
Tongue volume: Tongue volume will then be obtained by multiplying the mid-sagittal tongue cross-sectional area by the tongue width, as described in previous studies .
Lateral parapharyngeal wall thickness: The lateral parapharyngeal wall thickness will be measured with a linear probe placed laterally into the cervical region in the direction of the external auditory canal to visualize the branching of the carotid artery. The lateral edge of the pharynx will be visualized as a hyperechoic line. Vibration artifacts and pharyngeal position will be confirmed by swallowing the patient. The distance between the arteria carotid interna and the echogenic surface of the pharynx and the distance between the skin and the lateral wall of the pharynx will be measured .
Patients will be monitorized for critical respiratory events (CRE) postoperatively A PACU CRE is defined as, any unexpected hypoxemia (hemoglobin oxygen saturation \< 90%), hypoventilation (respiratory rate \< 8 bpm or arterial carbon dioxide tension \> 50 mmHg), or upper airway obstruction (stridor or laryngospasm) will be considered as requiring active and specific intervention (ventilation, tracheal intubation, opioid or muscle relaxant antagonism, oral/nasal airway or airway manipulation).
1. Upper airway obstruction requiring intervention (jaw thrust, oral airway);
2. Mild to moderate hypoxemia (SpO2=93%-90%) that does not improve after active interventions in 3 L nasal cannula oxygen (increasing O2 flows to \>3 L/min, high-flow surface application mask O2, verbal requests to breathe deeply, tactile stimulation);
3. Severe hypoxemia (SpO2\<90%) on 3 L nasal cannula O2, hypoxemia that does not improve after treatment (increased O2 flows \>3 L/min, high-flow face mask O2 application, verbal requests deep breathing, tactile stimulation);
4. Respiratory distress or signs of impending respiratory failure (respiratory rate \>20/min, use of accessory muscles, tracheal tugging);
5. Inability to take deep breaths when requested by the PACU nurse;
6. The patient complains of symptoms of respiratory or upper airway muscle weakness (difficulty breathing, swallowing or speaking);
7. Patient requiring reintubation in the PACU;
8. Clinical evidence or suspected pulmonary aspiration after tracheal extubation (gastric contents and hypoxemia observed in the oropharynx)
