Time | Group 1 (n: 33) | Group 2 (n: 33) | P-value* | ||
---|---|---|---|---|---|

Mean±SD | Median (min.–max.) | Mean±SD | Median (min.–max.) | ||

T1 | 0.52±0.23 | 0.58 (0.09–1)b | 0.47±0.33 | 0.42 (0–1)b | 0.342 |

T2 | 0.27±0.20 | 0.29 (0–0.71)a | 0.39±0.31 | 0.33 (0–1)ab | 0.173 |

T3 | 0.20±0.22 | 0.12 (0–0.62)a | 0.24±0.22 | 0.25 (0–0.67)a | 0.427 |

T4 | 0.15±0.17 | 0.17 (0–0.48)a | 0.23±0.24 | 0.20 (0–0.9)a | 0.226 |

P-value^{†} | <0.001 | <0.001 |

* Mann-Whitney U test,

^{†}Friedman test, SD: standard deviation, Min: minimum, Max: maximum, Group 1: 3 min at normal tidal volume, Group 2: 30 s with the 4 deep vital capacity technique, T1: after preoxygenation, T2: immediately after intubation, T3: at the 3rd min after intubation, T4: at the 7th min after intubation,^{*}*P*-value:comparison between groups.^{†}*P*-value: Compared within the group, a-b: There is no difference between times with the same letter in a group.