**3. Results**

Baseline characteristics are presented in Table 1. The younges<sup>t</sup> child was aged 13 months and the oldest 10 years and 10 months. Mean body weight was 19.5 ± 8.4 kg.

#### *3.1. Ventilation Parameters*

Comparison of RR, tidal volume (Vt), peak pressure, dynamic compliance, expiratory carbon dioxide concentration (etCO2), inspiratory oxygen fraction (FiO2) and quantity of gastric air at T0 (PEEP 5 mbar), T1 (PEEP 3 mbar) and T2 (PEEP 0 mbar) are shown in Table 2.


**Table 2.** Ventilation parameters and gastric air by PEEP.

For each PEEP level—with the only exception of respiratory rate, *p* = 0.3708—changes over time could be detected (each *p* < 0.0001) (Table 2).

There was a significant decrease in dynamic compliance as PEEP levels reduced (PEEP 5 > PEEP 3 > PEEP 0).

A significant increase in etCO2 concentration was observed with decreasing PEEP (PEEP 5 < PEEP 3 < PEEP 0). The inspiratory oxygen fraction (FiO2) was not significant.

The mean airway leak pressure was 22.5 ± 2 cmH2O.

#### *3.2. Gastric Air or Aspirates*/*Secretion*

An important endpoint of our study was the amount of gastric air or aspirates during mechanical ventilation with S-LMA and three different PEEP levels.

Also, for this parameter, changes over time have been found (*p* = 0.0176). Wilcoxon tests for two paired samples revealed significant differences between PEEP 5 and PEEP 3 (*p* = 0.0269) as well as PEEP 5 and PEEP 0 (*p* = 0.0209). We did not aspirate any gastric secretion.
