A nurse is caring for a patient with chronic obstructive pulmonary disease (COPD) who presents with the following arterial blood gas (ABG) results: pH 7.35, PaCO2 50 mmHg, HCO3- 26 mEq/L, PaO2 70 mmHg. The patient appears drowsy and has shallow respirations at 28 breaths per minute. What is the nurse's priority action?

Low-flow oxygen is prioritized in COPD to prevent CO2 retention while maintaining oxygenation. High-flow oxygen can suppress hypoxic drive, and other options may worsen ventilation.

Understanding the ABG Results
The patient's arterial blood gas (ABG) shows a pH of 7.35, which is on the acidic side of normal but not yet fully decompensated. The PaCO2 is elevated at 50 mmHg, and the HCO3- is 26 mEq/L, which is within normal limits. This pattern indicates an uncompensated respiratory acidosis. In a patient with chronic obstructive pulmonary disease (COPD), this is a classic presentation of an acute exacerbation superimposed on chronic CO2 retention. The primary problem is hypoventilation, evidenced by the drowsiness, shallow respirations, and elevated PaCO2.

The Danger of High-Flow Oxygen
Administering high-flow oxygen to a patient with chronic CO2 retention can be dangerous due to the loss of the hypoxic drive. In healthy individuals, the primary stimulus to breathe is an elevated PaCO2. However, patients with long-standing COPD often have chronically high CO2 levels, and their central chemoreceptors become desensitized to it. Their respiratory drive then shifts to rely on hypoxemia detected by peripheral chemoreceptors. If high-flow oxygen abruptly corrects the hypoxemia, it can remove this critical stimulus, leading to further respiratory depression, worsening hypercapnia, and potential respiratory arrest . The structural and functional changes in respiratory muscles described in chronic lung disease, including fiber-type shifts and reduced oxidative capacity, make these patients particularly vulnerable to the consequences of hypoventilation .

Why Low-Flow Oxygen is the Priority
The priority action is to correct the patient's hypoxemia (PaO2 70 mmHg) without suppressing their respiratory drive. Administering low-flow oxygen at 1-2 L/min via nasal cannula achieves this balance. This approach provides a controlled, small increase in inspired oxygen concentration, aiming for a target SpO2 of 88-92% in COPD patients at risk of hypercapnic respiratory failure. This is a standard of care that reflects a core competency in oxygen therapy knowledge and practice, which is critical for emergency nurses managing patients with complex respiratory conditions .

Why Other Options are Incorrect
Encouraging deep breathing exercises and incentive spirometry is inappropriate for a drowsy patient with shallow respirations who is in acute distress; this intervention requires patient alertness and cooperation. Placing the patient in the Trendelenburg position would worsen respiratory status by pushing abdominal contents against the diaphragm, further limiting lung expansion and ventilation. The correct nursing action is to first address the life-threatening hypoxemia in a manner that is safe for a CO2 retainer, which is controlled, low-flow oxygen therapy.