A 55-year-old chronic smoker presents with worsening dyspnea and cough with purulent sputum. Arterial blood gas analysis on room air reveals pH 7.31,…

This patient has an acute exacerbation of chronic obstructive pulmonary disease (COPD) presenting with acute-on-chronic hypercapnic respiratory failure (respiratory acidosis with elevated bicarbonate). The primary goal of oxygen therapy is to reverse hypoxemia while avoiding worsening hypercapnia and respiratory acidosis caused by ventilation-perfusion mismatch and Haldane effect. Controlled oxygen targeting SpO2 of 88-92% combined with non-invasive positive pressure ventilation (NIPPV) is the treatment of choice to decrease intubation rates and mortality.