PCV-VG Versus VCV Through the I-gel in Young Children

Patients in this group will receive mechanical ventilation using Pressure-Controlled Ventilation with Volume Guarantee (PCV-VG; Draeger AutoFlow or platform equivalent) through an i-gel supraglottic airway device following standard intravenous induction and muscle relaxation with atracurium.

Ventilation parameters: Target tidal volume (VT) set at 6-7 mL/kg ideal body weight (IBW), PEEP 4 cmH2O, I:E ratio 1:2, and age-stratified respiratory rate adjusted to maintain EtCO2 at 35-45 mmHg. The closed-loop algorithm dynamically auto-titrates inspiratory pressure (Pinsp) breath-by-breath based on the previous breath's expired tidal volume (VTe) to achieve target VT, with Pinsp safety ceiling capped at the individual baseline oropharyngeal leak pressure (OLP) minus 3 cmH2O (absolute maximum 20 cmH2O).

Administration of closed-loop pressure-controlled ventilation with volume guarantee via the i-gel supraglottic airway, maintaining target VT 6-7 mL/kg IBW with breath-by-breath inspiratory pressure auto-titration.

• PCV-VG

Patients in this group will receive standard mechanical ventilation using Volume-Controlled Ventilation (VCV) through an i-gel supraglottic airway device following standard intravenous induction and muscle relaxation with atracurium.

Ventilation parameters: Set tidal volume (VT) programmed at 6-7 mL/kg ideal body weight (IBW) with a constant square inspiratory flow waveform, PEEP 4 cmH2O, I:E ratio 1:2, and age-stratified respiratory rate adjusted to maintain EtCO2 at 35-45 mmHg. No active closed-loop leak-compensation or pressure-guarantee algorithm is engaged. Peak inspiratory pressure safety limit is set at baseline OLP minus 3 cmH2O (absolute maximum 20 cmH2O). If VTe falls > 20% below set VT for ≥ 3 consecutive breaths, VT may be up-titrated in 0.5 mL/kg IBW increments up to maximum 9 mL/kg IBW provided peak pressure remains below OLP.

Administration of traditional volume-controlled ventilation with constant inspiratory flow via the i-gel supraglottic airway, maintaining set VT 6-7 mL/kg IBW without automated pressure adaptation.

Measured in milliliters per kilogram of ideal body weight (mL/kg IBW) using the anesthesia workstation flow sensor. Evaluates delivery accuracy relative to the prescribed target (6.0-7.0 mL/kg IBW).

Values within the target prescribed range (6.0-7.0 mL/kg IBW) indicate a good result (effective alveolar ventilation). Values significantly below target (< 5.0 mL/kg IBW) indicate a bad result (hypoventilation due to circuit leak), while values above target (> 8.0 mL/kg IBW) indicate a bad result (risk of volutrauma).

Defined as an increase in serial radiologist-measured gastric antrum cross-sectional area (CSA) ≥ 20% from baseline (T0), confirmed on ≥ 2 of 3 measurements at either T1 or T2, calculated using the ellipse formula: CSA=(π × D1 × D2)/4 A lower percentage indicates a good result (enhanced gastric safety and effective airway seal). A higher percentage indicates a bad result (increased risk of gastric distension, elevated intra-abdominal pressure, and pulmonary aspiration).

Peak airway pressure measured in centimeters of water (cmH2O) directly from the anesthesia workstation pressure transducer.

A lower value indicates a good result (reduced risk of barotrauma and lower potential to exceed oropharyngeal leak pressure). A higher value indicates a bad result (increased pulmonary barotrauma risk and higher likelihood of driving gas into the esophagus).

Calculated using the formula: Cdyn= (VTe) ÷(Ppeak-PEEP), expressed in mL/cmH2O. A higher value indicates a good result (superior lung/thoracic compliance and lower resistance to inflation). A lower value indicates a bad result (stiffer lungs, higher airway resistance, or increased impedance).

Airway pressure in cmH2O at which an anterior cervical leak is detected on precordial auscultation during circuit occlusion.

A higher value indicates a good result (a tighter perilaryngeal device seal capable of sustaining higher positive pressure without leaking). A lower value indicates a bad result (poor device seal and higher risk of leak).

Measured in millimeters of mercury (mmHg) using continuous side-stream capnography on the anesthesia workstation to assess systemic ventilation status and carbon dioxide elimination.

Directional Interpretation: Values within the physiological target range (35-45 mmHg) indicate a good result (optimal normocapnic ventilation). Values significantly above target (> 45 mmHg) indicate a bad result (hypercapnia/hypoventilation due to circuit leak or dead-space rebreathing), while values below target (< 30 mmHg) indicate a bad result (hypocapnia due to hyperventilation).

Percentage calculated as: 100 × [(Duration of mechanical ventilation with EtCO2 > 50 mmHg)÷(Total Mechanical Ventilation Time)].

A lower percentage (ideally 0%) indicates a good result (effective carbon dioxide clearance throughout the surgical procedure). A higher percentage indicates a bad result (sustained alveolar hypoventilation or persistent leak leading to carbon dioxide retention).

Percentage calculated as: 100 × [(Breaths where Ppeak)> (Baseline OLP)÷ (Total Mechanical Breaths)].

A lower value (ideally 0%) indicates a good result (effective pressure containment within safe seal thresholds). A higher value indicates a bad result (frequent pressure spikes above the seal threshold, driving air into the stomach).

Composite incidence of laryngospasm, bronchospasm, oxygen desaturation (SpO2 < 93%), i-gel displacement, or endotracheal intubation conversion.

A lower percentage indicates a good result (superior airway safety and stability). A higher percentage indicates a bad result (increased perioperative respiratory complications).

Time in seconds from first device handling until capnographic confirmation of airway placement.

A lower value indicates a good result (faster, smoother airway securing). A higher value indicates a bad result (prolonged or difficult device placement).

PACU entry to achieving a modified Aldrete Score ≥ 9/10. A lower value indicates a good result (faster recovery and readiness for ward transfer). A higher value indicates a bad result (delayed recovery or lingering anesthetic effects).

Composite incidence of sore throat, hoarseness, or dysphagia assessed at 24 hours via telephone.

A lower percentage indicates a good result (minimal airway mucosal trauma). A higher percentage indicates a bad result (higher postoperative airway morbidity).