Table 2 Patient characteristics and preoperative risk factors for hypoxaemia (SpO2 < 95%) using univariate analysis

Age(yrs)

55 (44 ~ 63)

57 (48 ~ 65)

-3.466

0.001

BMI(kg/m²)

22.49 (20.57 ~ 24.45)

25.35 (23.42 ~ 27.74)

-15.792

 < 0.001

Abdominal girth(cm)

78 (73 ~ 83)

87 (80 ~ 93)

-15.894

 < 0.001

ASA physical status

-1.621

0.071

    I

301 (16.5%)

57 (14.84%)

    II

1475 (80.9%)

308 (80.20%)

    ≥ III

47 (2.6%)

19 (4.96%)

The modified Mallampati grade (MMP)

-25.202

 < 0.001

    I

1551 (85.1%)

93 (24.2%)

    II

254 (13.9%)

243 (63.3%)

    ≥ III

18 (1%)

48 (12.5%)

    Propofol dose (ug/kg/min)

181(152 ~ 233)

185(151 ~ 242)

-0.865

0.387

NoSAS related indexes

Male (n,%)

925 (50.7%)

211 (54.9%)

2.248

0.134

Age(yrs)

5.989

0.014

    ≤ 55

956 (52.40%)

175 (45.60%)

    > 55

867 (47.60%)

209 (54.4%)

Bullnecked (Neck circumference > 40cm)

124 (6.8%)

216 (56.3%)

595.107

 < 0.001

Snoring

195 (10.7%)

199 (51.80%)

365.818

 < 0.001

BMI(kg/m²)

-13.866

 < 0.001

    < 25

1469 (80.6%)

184 (47.9%)

    25 ~ 30

327 (17.9%)

160 (41.7%)

    ≥ 30

27 (1.5%)

40 (10.4%)

NoSAS scores

4 (2 ~ 6)

9 (4 ~ 11)

-16.904

 < 0.001

NoSAS ≥ 8

212 (11.6%)

224 (58.3%)

436.442

 < 0.001