Table 5. Muscle strength indices among the simple, difficult, prolonged, and failed weaning groups.

Variables	Simple	Difficult	Prolonged	Failed	P
Subjects	30	12	12	8	–
MRC score	51.1±11.4	44.2±9.8	37.3±17.7	44.1±14.6	0.025a
TwPtr, cmH2O	−16.7±8.5	−10.4±6.0	−9.3±2.5	−9.1±5.4	0.011b
NIF, cmH2O	−32.1±11.2	−25.6±9.7	−22.7±10.8	20.4±7.9	0.003c
Mortality (death)	2	2	4	3	<0.05d

^a, between the simple and failed weaning group; ^b, between the simple weaning group and non-simple weaning groups; ^c, between the simple weaning group and the prolonged and failed weaning groups; ^d, between the simple weaning group and the prolonged and failure groups. TwPtr, twitch tracheal airway pressure; NIF, negative inspiratory force; MRC, Medical Research Council.