Ninety adult patients from both gender, with acute respiratory failure, intubated and mechanically ventilated. Their ages ranged from 50 to 70 years. They were selected from Intensive Care Unit (ICU), Department of Chest Diseases, Cairo University Hospitals. They have randomly assigned into three equal groups. Group (A): trained by threshold IMT device plus routine physical therapy. Group (B): trained by adjusting MV trigger sensitivity plus routine physical therapy. Group (C): only received routine physical therapy. (Negative inspiratory force NIF, arterial blood gases, P/F ration, respiratory rate RR, tidal volume VT, and rapid shallow breathing index RSBI) were measured before the study and at the end of the study (just before weaning for successfully weaned patients, or on the 10 day of intervention for failed weaning patients).

Inclusion Criteria:

• Their age ranged from 50-70 years.
• The patients were diagnosed with acute respiratory failure duo to COPD exacerbation and need mechanical ventilation support for more than 48 hours.
• They were vitally stable and can tolerate pressure support
• PEEP less than 8Cm H2O , SpO2 more than 90).
• All patients were conscious and responded to verbal command.

Exclusion Criteria:

• Unstable hemodynamics,
• unstable neurological problems,
• lack of attention and cooperation
• skipping more than five training sessions.