Physiological parameters | Indices | Comments |
Pulmonary mechanics59 60 | Lung compliance (ml/cm H2O/kg) | Equivocal results |
Lung resistance (cm/H2O/l/s) | Poor discriminatory value of individual indices | |
Resistive work of breathing (gm × cm/kg) | Uncontrolled studies with fewer numbers | |
Pulmonary function61 | Functional residual capacity (ml/kg) | Measurement made soon after extubation |
Threshold value < 26 ml/kg for failure sensitivity 71% specificity 77% | ||
Effect of breathing and respiratory muscle endurance62-64 | Spontaneous breath tidal volume (ml/kg) | Not discriminatory |
Minute ventilation (ml/min/kg) (ratio of spontaneous : mechanical breaths) | Positive predictive value 86% but requires controlled study | |
Methodological inconsistency | ||
Mean inspiratory flow (VT/TI) | Different “threshold” values | |
Inspiratory pressure/maximal inspiratory pressure (PI/PIMAX) | ||
Composite data65 66(integrated indices) | Respiratory frequency and tidal volume | Not assessed in homogenous neonatal population |
Ratio (f/VT breaths/minute/l)CROP index (compliance, rate, oxygenation, and pressure) | Not discriminatory as in adults |
PI, inspiratory pressure; PImax, maximal inspiratory pressure; TI, inspiratory time; VT, tidal volume.