Vital capacity: >=10mL/kg
Peak voluntary negative inspiratory pressure: >20cmH2O
Tital volume >6ml/kg
Sustained titanic contraction(5sec)
T1/T4 ration >0.7
Alveolar-arterial PaO2 gradient (on FIO2 of 1.0): <350mmHg
Dead space to tidal volume ratio: ⇐0.6