Table 2 Univariate logistic regression and multivariate logistic analysis showing the association of variables with difficult tracheal intubation

 I

ref.

 II

4.787 (1.665, 13.766)

0.004

2.614 (0.799, 8.553)

0.112

 III

31.143 (10.540, 92.021)

<0.001

5.078 (1.451, 17.771)

0.011

 I/II

ref.

 III

1.744 (0.802, 3.794)

0.161

 IV

5.990 (3.082, 11.642)

<0.001

 male

ref.

 female

0.435 (0.242, 0.783)

0.006

 <11

ref.

 ≥11

0.009 (0.003, 0.023)

<0.001

0.022 (0.008, 0.061)

<0.001

 <32

ref.

 32-58

3.300 (0.436, 25.000)

0.248

1.156 (0.124, 10.799)

0.899

 ≥58

11.471 (1.562, 84.230)

0.016

3.150 (0.350, 28.361)

0.306

 <18.5

ref.

 [18.5,24)

0.789 (0.298, 2.091)

0.634

 [24,27)

0.841 (0.284, 2.490)

0.754

 [27-30)

1.972 (0.649, 5.990)

0.231

 ≥30

1.873 (0.436, 8.047)

0.399

 <65

ref.

 ≥65

0.302 (0.158, 0.575)

<0.001

 <35

ref..

 [35,40)

0.170(0.091,0.320)

<0.001

0.246 (0.110, 0.549)

0.001

 ≥40

0.023(0.008,0.067)

<0.001

0.109 (0.032, 0.377)

<0.001

 ≤55

ref.

 (55,62]

4.402(1.009,19.208)

0.049

6.251 (1.305, 29.938)

0.022

 >62

21.249(5.074,88.994)

<0.001

29.451 (6.212, 139.622)

<0.001