Inclusion Criteria:  Patients with respiratory failure in obesity hypoventilation syndrome and overlap syndrome, requiring ICU admission and fulfill criteria of NIMV supplementation (GOLD criteria 2021) patients with obesity hypoventilation syndrome and overlap syndrome diagnosed by polysomnogram or through STOP BANG Questionnaire or EPWORTH Sleepness Scale.  Exclusion Criteria:  Patients less than 18 years old Patients with hemodynamic instability Patients with central causes of hypercapnic respiratory failure Patients with disturbed conscious level Patients who refuse to participate in the study