A nurse is caring for a patient with chronic obstructive pulmonary disease (COPD) who presents with the following arterial blood gas (ABG) results: pH 7.25, PaCO2 70 mmHg, HCO3- 34 mEq/L, PaO2 55 mmHg. The patient appears drowsy but arousable, with shallow respirations at 28 breaths per minute and oxygen saturation of 88% on room air. What is the priority nursing intervention?

The ABG indicates chronic respiratory acidosis with partial metabolic compensation, requiring low-flow oxygen to prevent CO2 retention while addressing hypoxia. High-flow oxygen or Trendelenburg position can exacerbate CO2 retention, and deep breathing alone is insufficient for oxygenation.

ABG Interpretation and Clinical Presentation
The patient's arterial blood gas (ABG) reveals a pH of 7.25, a PaCO₂ of 70 mmHg, and an HCO₃⁻ of 34 mEq/L. This pattern indicates a primary respiratory acidosis with partial metabolic compensation. The pH is below 7.35, confirming acidemia, while the markedly elevated PaCO₂ points to hypercapnic acute respiratory failure (ARF) as the underlying cause. The elevated bicarbonate level reflects the kidneys' attempt to retain HCO₃⁻ over time, which is a hallmark of a chronic condition like chronic obstructive pulmonary disease (COPD). The concurrent hypoxemia (PaO₂ 55 mmHg) and low oxygen saturation (88% on room air) complete the picture of decompensated respiratory failure. The patient's drowsiness and shallow, rapid breathing are classic signs of CO₂ narcosis and impending respiratory muscle fatigue.

Priority Nursing Intervention and Rationale
The priority is to administer low-flow oxygen therapy at 1-2 L/min. In patients with chronic hypercapnia, the respiratory drive can shift from a primary reliance on elevated CO₂ levels to a dependence on hypoxic drive. Administering high concentrations of oxygen can suppress this drive, leading to further hypoventilation, worsening hypercapnia, and potentially causing respiratory arrest. The goal is to correct life-threatening hypoxemia cautiously, targeting an oxygen saturation of 88-92%, which is sufficient for tissue oxygenation without completely abolishing the hypoxic stimulus to breathe.

Analysis of Incorrect Options

- Option 2: Encourage deep breathing and coughing exercises every 2 hours. While these are important components of COPD management to mobilize secretions and improve ventilation, they are not the immediate priority. This patient is in acute respiratory failure with altered mental status and is likely too fatigued to perform these exercises effectively. The immediate threat is severe hypoxemia, which must be addressed first.
- Option 3: Administer high-flow oxygen at 6 L/min via face mask. This is a dangerous intervention for this specific patient. High concentrations of supplemental oxygen can blunt the hypoxic respiratory drive, leading to a precipitous rise in PaCO₂, worsening acidosis, and potential respiratory arrest. This principle is critical even as newer technologies emerge; the foundational approach to oxygen therapy in acute hypercapnic COPD exacerbation remains controlled, low-flow delivery.
- Option 4: Position the patient in Trendelenburg position to improve ventilation. The Trendelenburg position (head down, feet elevated) pushes the abdominal contents against the diaphragm, mechanically restricting its movement and worsening ventilation in a patient who is already breathing shallowly. The optimal position for a COPD patient in respiratory distress is upright or semi-Fowler's to maximize diaphragmatic excursion.

Connecting Evidence to Clinical Practice
The foundational management of hypercapnic ARF, particularly in acute COPD exacerbation, involves a stepwise approach. While the provided evidence highlights the role of advanced therapies like non-invasive ventilation (NIV) as the first-line ventilatory strategy and explores the potential of high-flow nasal cannula (HFNC) ^[1], it does not negate the immediate, life-saving intervention of controlled oxygen therapy. The study by Nilius et al. investigates NHF in COPD patients with chronic respiratory failure, focusing on physiological effects like tidal volume and gas exchange, which is a step beyond the acute stabilization phase. Similarly, the meta-analysis by Lin et al. compares HFNC to conventional oxygen therapy in a postoperative setting, a context distinct from a hypercapnic COPD exacerbation where hypoxic drive is a primary concern. The critical nursing judgment here is recognizing that before initiating any positive-pressure support, the immediate threat of severe hypoxemia must be reversed in a manner that does not precipitate respiratory depression. Controlled, low-flow oxygen is the essential first step that bridges the gap to these more advanced therapies.