Inspiratory muscle fatigue
Dynamic hyperinflation in COPD patients leads to
flattening of diaphragm. Its contraction requires more
work of breathing being at flat part of length-tension
relationship. Levine et al.[11] found significant diaphragmatic
muscle atrophy in patients mechanically ventilated for
18–96 h. Isolated measurement of Maximal Inspiratory
Pressure does not take into account inspiratory muscle
endurance; hence, its role as a weaning predictor is
controversial.[5] Absence of hypercapnia in a weaning‑failure
patient virtually excludes inspiratory muscle fatigue.
Rehabilitation and muscle retraining with inspiratory
muscle training has an important role in successful weaning
in patients unable to wean. Antioxidant supplementation
with N acetylcysteine may attenuate low‑frequency
human diaphragm fatigue and has been shown to reduce
ventilator‑dependent days.