Objectives : Acute respiratory failure is a common clinical condition encountered in emergency department and intensive care units (ICU). The use of NIV during acute respiratory failure (ARF) has increased since the late 1990s for all diagnoses, including patients with and without chronic obstructive pulmonary disease (COPD). The use of NIV is associated with reduced tracheal intubation, duration of hospitalization, and mortality.
Aim of the work: To evaluates the effectiveness of Non invasive ventilation in the management of acute hypercapnic respiratory failure of different aetiologies as acute exacerbation of COPD, and acute hypoxemic respiratory failure.
Design of study:  Prospective, Observational, Single-center study.
Patients  and Methods: 103 patients with acute respiratory failure (ARF) were admitted to Respiratory Intensive Care Unit (RICU) of Chest Department at Assuit University Hospital and received non invasive ventilation, in all patients demographic , clinical and functional parameters were recorded including the cause of acute respiratory failure . NIV success was defined as clinical and gasometric improvement and discharge to regular ward, while need of endotrachial intubation was considered NIV failure.
 Results:  one hundred and three patients with mean age 59.1 years were included in the study,62 (60%) were males and 41(40%) were females, Baseline pH, PaCO2 and PaO2 were 7.51±0.09, 72±21.63and 59.41±20.34 mmHg respectively.
The success rate with NIPPV was 69%, with 71of 103 patients weaned successfully. Significant improvements were observed at 2 hour,24-48hrs following institution of NIPPV in pH (7.34±0.08, P < 0.02), PaCO2 (62.87±17.94, P < 0.002) and PaO2(74.30±14.45 P < 0.001).These improvements maintained (within 24 hrs) postweaning from the ventilator, pH 7.39±0.04, PaCO2 56.76±10.18, PaO2 73.28±10.04 ( P < 0.001).
Duration of mechanical ventilation , length of ICU stay were significantly longer in NIV failure group (p<0.0001). , the complications and death were significantly higher in NIV failure group (p<0.00001),(p<0.0001).
Serum albumin level was significantly lower in the NIV failure group (p<0.01).
Conclusion: The use of NIV in patients presenting with ARF of diverse etiology
has shown to be effective in the improvement of clinical and gasometric parameters, in preventing endotracheal intubation, and improving overall survival