A nurse is reviewing arterial blood gas (ABG) results for a patient with chronic obstructive pulmonary disease (COPD) who presents with acute respiratory distress. The ABG results show: pH 7.32, PaCO₂ 58 mmHg, HCO₃⁻ 28 mEq/L, PaO₂ 68 mmHg. What is the nurse's priority action?
1Administer high-flow oxygen at 15 L/min via non-rebreather mask
2Prepare for immediate endotracheal intubation
3Position the patient to optimize breathing and encourage breathing techniques✓ 정답
4Administer sodium bicarbonate to correct the acidosis
해설
The ABG indicates respiratory acidosis with compensation, common in COPD exacerbations. Positioning and breathing techniques improve ventilation and CO2 removal without risks of oxygen-induced hypercapnia or unnecessary interventions. High-flow oxygen can suppress respiratory drive, intubation is premature without severe failure, and bicarbonate is not indicated for respiratory acidosis.
Understanding the ABG in COPD Exacerbation
The arterial blood gas (ABG) results reveal a state of acute-on-chronic respiratory acidosis. The pH is 7.32 (acidotic), the PaCO₂ is 58 mmHg (elevated), and the HCO₃⁻ is 28 mEq/L (elevated). This pattern is classic for a patient with COPD who is experiencing an acute exacerbation. The chronically elevated PaCO₂ has led to renal compensation, which is why the bicarbonate level is higher than the normal range of 22-26 mEq/L; the kidneys have been retaining HCO₃⁻ to buffer the chronic respiratory acidosis. The acute-on-chronic nature is indicated by the pH falling below 7.35, showing that the current respiratory distress has overwhelmed the body’s compensatory mechanisms. The PaO₂ of 68 mmHg indicates hypoxemia, which is typical in this scenario .
Prioritizing Non-Invasive Interventions
The priority action is to position the patient to optimize breathing and encourage breathing techniques. In the initial assessment and management of respiratory distress, guidelines emphasize a stepwise approach, beginning with the least invasive and most immediately accessible interventions [2]. For a patient with COPD who is still conscious and has a patent airway, the first-line nursing actions are to optimize ventilation and gas exchange through positioning, such as the tripod position or high-Fowler's position, and to coach the patient in techniques like pursed-lip and diaphragmatic breathing. These maneuvers help to reduce dynamic hyperinflation, decrease the work of breathing, and facilitate CO₂ exhalation, directly addressing the hypercapnia that is driving the acidosis [1,2].
Why the Other Options Are Incorrect
- Administer high-flow oxygen at 15 L/min via non-rebreather mask: This action is dangerous for a patient with chronic CO₂ retention. In some COPD patients, the respiratory drive shifts to rely on the hypoxic drive rather than the normal hypercapnic drive. Administering uncontrolled, high-flow oxygen can suppress this hypoxic drive, leading to further hypoventilation, a dangerous rise in PaCO₂, and worsening acidosis and somnolence. The goal is to titrate oxygen to a target saturation of 88-92% using a controlled delivery device like a Venturi mask or nasal cannula [1,2].
- Prepare for immediate endotracheal intubation: Intubation is a definitive but highly invasive procedure reserved for patients who fail non-invasive interventions, such as those with a declining level of consciousness, respiratory arrest, or failure of non-invasive ventilation. Guidelines for initial assessment stress exhausting non-invasive strategies first [2]. The scenario does not provide evidence of a failed airway or imminent respiratory arrest, making this a premature and non-priority action.
- Administer sodium bicarbonate to correct the acidosis: Administering sodium bicarbonate to correct a respiratory acidosis is not indicated and can be harmful. The underlying problem is hypoventilation leading to CO₂ retention. The definitive treatment is to improve ventilation and blow off the excess CO₂. Giving bicarbonate would only provide a temporary, ineffective buffer and could lead to a paradoxical worsening of intracellular acidosis as the bicarbonate is converted to CO₂, which readily crosses cell membranes .
References (research sources)
[2]
Guidelines for the Initial Assessment of Respiratory Distress in the Emergency Department.GuidelineLe Borgne P, Thille AW, Guenezan J, Aissaoui N, Boureau AS, Bally C, Balen F, Basset A, Bilbault P, Boissier F, Claessens YE, Decavèle M, Diehl JL, Douillet D, Guillon A, Hausfater P, Javaudin F, Jezequel M, Kuteifan K, L'Her E, Marjanovic N, Maury E, Ohana M, Pichereau C, Ray P, Reuter PG, Tiberti N, Voiriot G, Yordanov Y, Le Conte P, Terzi N. (2026) · DOI: 10.1016/j.aicoj.2025.100005
Clinical Management Guide: COPD Exacerbation with Acute-on-Chronic Respiratory Acidosis
Initial Assessment & Non-Invasive Interventions
Positioning: Immediately assist the patient into a high-Fowler's or tripod position. This optimizes lung expansion by reducing pressure from abdominal contents and facilitating use of accessory muscles.
Breathing Techniques: Coach the patient in pursed-lip and diaphragmatic breathing. These techniques reduce dynamic hyperinflation, slow the respiratory rate, and improve tidal volume and gas exchange.
Oxygen Therapy: Initiate controlled, low-flow oxygen (e.g., 24-28% via Venturi mask or 1-2 L/min via nasal cannula). Titrate to achieve a target SpO2 of 88-92% to correct hypoxemia without blunting the hypoxic drive.
Escalation & Monitoring
Non-Invasive Ventilation (NIV): If the patient does not improve with positioning and controlled oxygen, prepare for a trial of BiPAP or CPAP. NIV is the standard of care to avoid intubation in moderate to severe COPD exacerbations.
Pharmacological Support: Administer bronchodilators (short-acting beta-agonists and anticholinergics) via nebulizer and systemic corticosteroids as prescribed to reduce airway inflammation and bronchospasm.
Reassessment: Continuously monitor mental status, work of breathing, and repeat ABG within 30-60 minutes of intervention. Signs of deterioration (worsening pH, rising PaCO2, altered consciousness) indicate a need for intubation.
Key Safety Considerations
Avoid High-Flow Oxygen: Never apply a non-rebreather mask at high flow rates as a first-line measure in known CO2 retainers due to the risk of inducing respiratory depression and worsening hypercapnia.
Do Not Administer Sodium Bicarbonate: This does not address the underlying ventilatory problem and can cause paradoxical intracellular acidosis and increased CO2 production.
Acute-on-Chronic Respiratory Acidosis — A state where a chronic respiratory condition like COPD acutely worsens, causing a further rise in PaCO2 and a drop in pH despite existing renal compensation (elevated HCO3).
Hypoxic Drive — A respiratory drive mechanism in some chronic CO2 retainers where the primary stimulus to breathe comes from low PaO2 rather than high PaCO2; high-flow oxygen can blunt this drive.
Pursed-Lip Breathing — A breathing technique that creates back pressure in the airways, helping to keep them open longer during exhalation to reduce air trapping and improve gas exchange.
Tripod Position — A sitting position where the patient leans forward with arms braced on knees or a table, which optimizes the use of accessory muscles and improves diaphragmatic excursion.