Table 7.
Comparison of weaning indices
| Index | Cut off value | Equation/Measurement | Remarks |
|---|---|---|---|
| Respiratory rate (RR) | <30/min | – Simple – Part of a routine monitoring |
|
| Tidal volume (Vt) | >5 mL/kg | – By Spirometer if patient is on T-piece – By Ventilator expiratory parameters if patient is on PSV by keeping PSV and PEEP at 0 |
– Require spirometer – Part of a routine monitoring on ventilator screen |
| Forced vital capacity (FVC) | >15 mL/kg | Same as Tidal Volume | Difficult to measure in all patients |
| Minute ventilation | <15 L/min | Vt x RR | Easy to measure |
| Rapid shallow breathing index (RSBI) | <105 breaths/min/L | f/Vt: frequency/Vt | – Most studied – Easy to measure – Very popular – Simple to measure – High sensitivity but less specificity |
| Maximum inspiratory pressure (PImax) | < –30 cm H2O (Normal: –90–120 cm H2O) | Breathing with ventilator valves closed (Pimax Maneuver) | Requires patient's co-operation |
| P0.1/PImax | > 0.3 P0.1 is pressure at the airway opening 0.1 s after start of inspiratory flow |
P0.1/PImax | – Complex – No added advantage |
| P0.1 x f/VT | <300 | Less studied | |
| Dynamic compliance, rate, oxygenation, max inspiratory pressure (CROP index) | >13 | (Cdyn × PImax × (PaO2/PAO2)/f | Complex |
| Dynamic compliance, oxygenation, rate, effort (CORE index) | >8 | Cdyn × (PImax/P0.1) × (PaO2/PAO2)/f | – Complex |
| Weaning index (WI) | <50 | RSBI × EI × VDI (EI: peak pressure /negative inspiratory force; VDI: MV/10) |
– Complex |
| integrative weaning index (IWI) | >25 | (CRS × SaO2)/(f/VT) (CRS = Static compliance of the respiratory system) |
– Very complex – Labor intensive |
| Heart rate, acidosis, consciousness, oxygenation, respiratory rate (HACOR) | ≥5 | Predicts weaning failure | – Complex – More validated for predicting NIV failure |
| Diaphragmatic RSBI | 1.767 | RR/diaphragmatic displacement (in millimeters) and expressed as breath/minute/millimeter. | – Predicts weaning failure – Requires expertise – Require larger study |
| Minute ventilation recovery time | Calculated before and 30 min after SBT | – Simple but in accurate – Multiple confounding factors |