Predictors of non-invasive ventilation outcome in acute exacerbation of COPD with hypercapnic respiratory failure: a prospective observational study from a tertiary-care respiratory unit

Abstract

Background
Chronic Obstructive Pulmonary Disease (COPD) is a leading cause of morbidity and mortality worldwide, with acute exacerbations (AECOPD) often resulting in hypercapnic respiratory failure requiring ventilatory support. Non-invasive ventilation (NIV) has become the preferred first-line therapy in such cases; however, early prediction of NIV failure remains crucial for optimizing outcomes and preventing delayed intubation.


Objective
To identify clinical, biochemical, and physiological predictors associated with NIV success or failure in patients with AECOPD presenting with hypercapnic respiratory failure.


Methods
This prospective observational study was conducted over 18 months in the Respiratory Care Unit of a tertiary-care center. A total of 130 eligible AECOPD patients (pH < 7.35, PaCO₂ > 45 mmHg) treated with NIV were enrolled. Patients requiring immediate intubation or having contraindications to NIV were excluded. Serial clinical assessment, arterial blood gases (ABG), and organ dysfunction scores were monitored at baseline and during NIV. NIV failure was defined as intubation or in-hospital death. Data were analyzed using SPSS v23, and predictors were determined by multivariate logistic regression.


Results

NIV was successful in 92 (70.8%) and failed in 38 (29.2%) patients; 16 patients (12.3%) died during hospitalization. Baseline demographic, clinical, and biochemical parameters were not significantly associated with NIV outcome. Independent predictors of NIV failure were a SOFA score ≥6 (OR 2.9; 95% CI 1.5–5.4;
p
=0.004) and pH improvement <0.03 within 6 h of NIV initiation (OR 3.4; 95% CI 1.8–6.3;
p
=0.002). Complications such as shock, pneumonia, arrhythmia, and acute kidney injury were significantly higher in the failure group. NIV failure was associated with prolonged ICU and hospital stay (
p
<0.01).



Conclusion
In AECOPD with hypercapnic respiratory failure, early physiological response—particularly pH improvement within six hours—and baseline organ dysfunction (SOFA ≥6) are strong independent predictors of NIV failure. Structured monitoring of ABG and organ scores during the first 24 h can guide timely escalation and improve clinical outcomes.