Number of Patients:

Total no. of patients = 40 patients NIV-PSV group (Group A) = 20 NIV-NAVA group (Group B) = 20

Inclusion criteria

a) Patients of Chronic obstructive pulmonary disease with acute hypercapnic respiratory failure (pH < 7.35 and PaCO2 >45 mmHg) requiring noninvasive ventilation and with no indication for invasive mechanical ventilation.

Exclusion criteria

1. Patient with any contra-indication for insertion of nasogastric tube (like recent gastrointestinal bleeding in previous 30 days, esophageal varices)
2. Patient with any contraindication of noninvasive ventilation (such as hemodynamic instability, active gastrointestinal bleed etc)
3. Patients with a known neuromuscular, central or peripheral nervous system disorder.
4. Patient not willing to give consent.

Control(s): Patients receiving pressure support ventilation (NIV-PSV) will act as control

Study design: Randomized interventional study

Dosages of drug: None

Duration of treatment: Till patient improves or requires invasive ventilation.

Brief Methodology Patients of COPD with acute exacerbation will be randomized into two groups (group A and group B) to receive NIV-PSV or NIV-NAVA respectively. A special naso-gastric catheter (EAdi-catheter) will be placed in all patients. In each mode, NIV will be applied using a non-vented oro-nasal mask that will be fitted enough to avoid air leaks. Patients in Group A will receive NIV-PS and Group B will receive ventilation via NIV-NAVA. Pressure support and PEEP levels will be set by the treating physician to achieve a tidal volume (Vt) of 6 to 8 mL/kg of ideal body weight. NAVA level will be adjusted to match peak pressures of NIV-PSV using manufacturer-supplied software. After stabilization, a 30-min period of each NIV trial will be recorded and manually analyzed offline. Subsequent readings will be taken at 2, 6 and at 24 hours and then at 6 hourly interval from day 2 onwards. In each trial, patient-ventilator asynchronies (ineffective efforts, auto triggering, premature cycling, delayed cycling, and double triggering) will be determined on EAdi, airway pressure, and flow signal. The number of each type of asynchrony, defined as the number of events per minute, will be determined for each recording period. The asynchrony index (AI), in percentage, will be calculated as described previously, and an AI >10% will be considered severe asynchrony. Patient comfort level after each mode of ventilation will be assessed by using visual analogue scale. Various clinical, ventilatory and arterial blood gas parameters will be recorded.

Statistical analysis Data will be expressed as mean ± standard deviation (SD), or percentage. Differences in continuous variables between the two groups will be compared using student's t test (or Mann-Whitney U test); while differences in categorical data will be compared using the chi- square test (or Fisher's exact test). A p value of less than 0.05 will be considered statistically significant.

Inclusion Criteria:

• Patients of Chronic obstructive pulmonary disease with acute hypercapnic respiratory failure requiring noninvasive ventilation and with no indication for invasive mechanical ventilation will be included in the study.

Exclusion Criteria:

• Patient with any contraindication for insertion of nasogastric tube (like recent gastrointestinal bleeding in previous 30 days, Esophageal varices)
• Patient with any established contraindication of noninvasive ventilation. (Like Hemodynamic instability, active GI bleed etc)
• Patients with a known neuromuscular, Central or peripheral nervous system disorder.
• Patient not willing to give consent.

Will share, if required