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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