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Table 2 Ventilator variables, respiratory indices and results of first spontaneous breathing trial

From: Variables predicting weaning outcome in prolonged mechanically ventilated tracheotomized patients: a retrospective study

Ventilator variables, respiratory indices, and results of first SBT

All patients (n = 263)

Weaning success (n = 126)

Weaning failure (n = 137)

P valuea

Ventilator variables

 IPAP (cmH2O)

23.4 (± 4.8)

21.7 (± 4.4)

24.9 (± 4.6)

< 0.001b

 PEEP (cmH2O)

5.9 (± 1.2)

5.6 (± 0.8)

6.1 (± 1.5)

< 0.001b

 DP (cmH2O)

17.5 (± 4.5)

16.1 (± 4.2)

18.7 (± 4.5)

< 0.001b

 VTi (mL)

534 (± 82)

535 (± 81)

533 (± 82)

0.416b

 BF (breaths/min)

16.2 (± 2.5)

16.1 (± 2.6)

16.3 (± 2.4)

0.288b

 VE (L/min)

8.6 (± 1.8)

8.6 (± 1.7)

8.7 (± 1.9)

0.306b

 Oxygen flow on MV (L/min)

2.6 (± 1.8)

2.5 (± 1.7)

2.7 (± 1.8)

0.123b

Respiratory indices

 LTC (mL/cmH2O)

32.8 (± 10.8)

35.5 (± 11.1)

30.3 (± 9.9)

< 0.001b

 Mechanical power (J/min)

19.8 (± 5.9)

18.4 (± 5.3)

21.2 (± 6.1)

< 0.001b

 PBW-MP (J/min/kg PBW × 10-3)

277 (± 87)

252 (± 79)

299 (± 88)

< 0.001b

 LTC-MP (J/min × cmH2O/mL × 10-3)

685 (± 348)

585 (± 297)

777 (± 366)

< 0.001b

 VE-MP (J/L)

2.29 (± 0.47)

2.13 (± 0.43)

2.44 (± 0.45)

< 0.001b

 Ventilatory ratio

1.14 (± 0.27)

1.07 (± 0.26)

1.20 (± 0.28)

< 0.001b

First SBT

Time from admission to first SBT (days)

2.5 (± 4.2)

2.1 (± 4.2)

2.9 (± 4.3)

0.056b

Hemoglobin on first SBT (g/dL)

8.8 (± 1.2)

8.7 (± 1.2)

8.9 (± 1.2)

0.085b

PaCO2 on aBGA

 PaCO2 on MV pre-SBT (mmHg)

35.7 (± 5.0)

34.2 (± 4.8)

37.0 (± 4.8)

< 0.001b

 PaCO2 post-SBT (mmHg)

39.1 (± 6.5)

36.8 (± 5.7)

41.5 (± 6.3)

< 0.001b

 ∆PaCO2 (pre-/post-SBT)

3.4 (5.5)

2.5 (± 4.8)

4.4 (± 5.9)

0.005c

pH on aBGA

 pH on MV pre-SBT

7.48 (± 0.05)

7.50 (± 0.05)

7.47 (± 0.05)

< 0.001b

 pH post-SBT

7.45 (± 0.05)

7.47 (± 0.05)

7.43 (± 0.05)

< 0.001b

 ∆pH (pre-/post-SBT)

− 0.03 (± 0.05)

− 0.03 (± 0.05)

− 0.04 (± 0.06)

0.025b

PaO2 on aBGA

 PaO2 on MV pre-SBT (mmHg)

81.4 (± 18.7)

81.9 (± 17.4)

80.9 (± 19.9)

0.325b

 PaO2 post-SBT (mmHg)

74.3 (± 17.2)

76.3 (± 18.9)

72.2 (± 15.0)

0.036b

 ∆PaO2 (pre-/post-SBT)

6.9 (± 22.3)

6.2 (± 24.4)

7.7 (± 19.8)

0.293b

Duration of first SBT (min)

27.0 (± 7.5)

28.8 (± 4.9)

25.2 (± 9.0)

< 0.001b

Reason for failure of first SBT

72 (27.4)

12 (9.5)

60 (43.8)

< 0.001c

 Acidosis post-SBT

10 (3.8)

2 (1.6)

8 (5.8)

0.072d

 Hypercapnia post-SBT

37 (14.1)

6 (4.8)

31 (22.6)

< 0.001c

 Premature termination of SBT

42 (16.0)

8 (6.3)

34 (24.8)

< 0.001c

  1. Continuous variables are presented as mean values (± standard deviation); categorical variables are presented as number (%)
  2. aP value for differences between patients with weaning success and weaning failure
  3. bStudent’s t test
  4. cChi-squared test
  5. dFisher’s exact test
  6. IPAP inspiratory positive pressure ventilation, PEEP positive end-expiratory pressure, DP driving pressure, VTi inspiratory tidal volume, BF breathing frequency, VE minute ventilation, MV mechanical ventilation, LTC dynamic lung-thorax compliance, MP, mechanical power, J joule, PBW-MP mechanical power normalized to predicted body weight, PBW predicted body weight, LTC-MP mechanical power normalized to dynamic lung-thorax compliance, VE-MP mechanical power normalized to minute ventilation, aBGA arterial blood gas analysis, SBT spontaneous breathing trial