This study will use different indices for prediction of NIV failure in ARF patients Evaluation of HACOR score and ROX index for early prediction of NIV failure in patients with ARF.

Study value of diaphragmatic dysfunction assessed by ultrasound as tool for prediction of success of NIV in ARF patients.

Compare clinical significance of these scoring systems between hypoxemic and hypercapnic RF

Noninvasive ventilation (NIV) is a useful and safe method to improve gas exchange in patients with acute respiratory failure (ARF) of different etiologies. NIV reduces the work of breathing, improves arterial oxygenation and alveolar ventilation. It is associated with improved survival in the acute care setting (Cabrini L 2015) when compared to conventional oxygen therapy. As NIV offers several major advantages over invasive ventilation (e.g., preserving the ability to swallow, cough, and communicate verbally), it is widely used to avoid intubation.

Although NIV nowadays is frequently used, its failure rate remains high (25-59%), indicating that not all patients benefit from this treatment. There is an association between the unsuccessful NIV and the poor outcome has been suggested. Among patients who experience NIV failure, either premature or delayed NIV discontinuation further increases mortality. Thus, identifying the predictors of NIV failure is crucial because of the strong link between failure and poor outcomes. So, researchers woke to make scoring systems that may predict NIV failure, as HACOR and ROX indices.

Recently, ultrasonography (US) of the diaphragm as a bedside method is used for evaluation of diaphragmatic function and predicting failure of NIV in acutely ill patients.

Up till now there is limited research to support significance of different indices for prediction of NIV failure and need for invasive mechanical ventilation (IMV).

Inclusion Criteria:

1. Patients with acute hypoxic respiratory failure who need Noninvasive ventilation.
2. Patients with acute hypercapnic respiratory failure who need Noninvasive ventilation.

Exclusion Criteria:

1. Age < 18 years old.
2. Patients with unconsciousness, severe hemodynamic instability, unable to fit mask (Recent facial surgery, trauma, or deformity), inability to protect the airway or clear respiratory secretions or any other contraindication of NIV.
3. neuromuscular disease or chest wall deformities.
4. Pregnancy.
5. NIV intolerance.
6. severe obesity with Body Mass Index (BMI)≥35 kg/m2

Patients of both gender with acute respiratory failure either hypoxic or hypercapnic who need Noninvasive ventilation.