Table 2.
Ventilator variables, respiratory indices and results of first spontaneous breathing trial
| 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 |
Continuous variables are presented as mean values (± standard deviation); categorical variables are presented as number (%)
aP value for differences between patients with weaning success and weaning failure
bStudent’s t test
cChi-squared test
dFisher’s exact test
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