High pressure NIV is a pressure limited ventilation, stating IPAP pressure at 20 cmH2O and gradually increasing pressure up to 30 cmH2O according to patient tolerance.

Noninvasive ventilation (NIV): refers to the administration of ventilatory support without using an invasive artificial airway (endotracheal tube or tracheostomy tube). NPPV is well established in the management of acute on chronic hypercapnic respiratory failure secondary to acute exacerbation of COPD (AECOPD), obesity hypoventilation syndrome, and restrictive thoracic disorders.

During the past years NIV was applied by using low pressure inspiratory positive airway pressure (IPAP), which means titrating inspiratory pressure starting at 10 cmH2O and increasing pressure gradually according to patient tolerance maximum up to 20 cm H2O.

There is still about 15% failure rate while using conventional low pressure NIV, this failure rate may be attributed to the following:

1. Still in a number of patients with conventional low pressure NIV, PaCO2, and pH worsen with subsequent deterioration and need for invasive ventilation.
2. Despite lowering PaCO2 value with conventional NIV ventilation but it is not normalized so with minimal derangement in clinical condition of the patient it worsens again.
3. Also abnormally high level PaCO2 may have a negative impact on vital organs.
4. Low pressure may be associated with patient intolerance , and discontinuation of NIV.

Recently high pressure NIV used aiming to improve outcome of NIV. High pressure NIV is a pressure limited ventilation, stating IPAP pressure at 20 cmH2O and gradually increasing pressure up to 30 cmH2O according to patient tolerance. High pressure NIV is expected to improve alveolar ventilation, decreasing dead space ventilation, and work of breathing, so it can improve the outcome result .

Inclusion Criteria:

All patients admitted in Assiut University Hospital and Assiut Police Hospital with acute hypercapnic respiratory failure due to COPD and Obesity hypoventilation syndrome (OHS) indicated for conventional NIV.

Patients who failed on low pressure NIV will be shifted to high pressure NIV with any of these conditions:

1. PH <7.30 or less than admission level.
2. RR > 35b/m or more than admission level.
3. SpO2 < 88%.

Exclusion criteria: (4)

1. Age <18 years.
2. Excessive amount of respiratory secretions or weak cough.
3. Upper airway obstruction.
4. Recent oral, facial or cranial trauma or surgery.
5. Sever abdominal distension.
6. Active upper gastrointestinal bleeding.
7. Cardiac or respiratory arrest.
8. PH<7.25.
9. Arterial oxygen tension /fraction of inspired oxygen (PaO2 / FiO2) <150mmHg.

Patients who failed on low pressure NIV will be shifted to high pressure NIV with any of these