# A nurse is caring for a patient with chronic obstructive pulmonary disease (COPD) who has the following arterial blood gas (ABG) results: pH 7.28, PaCO₂ 55 mmHg, HCO₃⁻ 26 mEq/L, PaO₂ 70 mmHg. What is the most appropriate nursing intervention for this patient?

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## 문제

A nurse is caring for a patient with chronic obstructive pulmonary disease (COPD) who has the following arterial blood gas (ABG) results: pH 7.28, PaCO₂ 55 mmHg, HCO₃⁻ 26 mEq/L, PaO₂ 70 mmHg. What is the most appropriate nursing intervention for this patient?

## 보기

1. Encourage deep breathing exercises and coughing techniques
2. Position the patient in high Fowler's position and administer low-flow oxygen **✔ 정답**
3. Prepare for immediate intubation and mechanical ventilation
4. Administer sodium bicarbonate as ordered by the physician

**정답: 2**

## 해설

The ABG shows compensated respiratory acidosis with mild hypoxemia in COPD. Positioning in high Fowler's and low-flow oxygen optimize ventilation while avoiding CO2 narcosis. Other options are less appropriate: deep breathing is insufficient, intubation is not indicated, and sodium bicarbonate is not needed for compensated acidosis.

## 심화 해설

Understanding the ABG Results

First, let's interpret the arterial blood gas (ABG) values. The patient has a pH of 7.28, which is below the normal range of 7.35-7.45, indicating acidosis. The PaCO₂ is 55 mmHg (normal 35-45 mmHg), which is elevated. An elevated PaCO₂ points to a respiratory acidosis. The HCO₃⁻ is 26 mEq/L, which is within the normal range (22-26 mEq/L). This lack of metabolic compensation suggests the respiratory acidosis is acute in nature. This clinical picture is consistent with an acute exacerbation of chronic obstructive pulmonary disease (COPD) leading to hypercapnic acute respiratory failure (ARF) [1].

Analyzing the Intervention Options

The goal of treatment is to improve ventilation and gas exchange while avoiding harm. Let's evaluate the options based on the underlying pathophysiology.

Option 1: Encourage deep breathing exercises and coughing techniques.

While these techniques are beneficial for airway clearance and preventing atelectasis in stable patients, they are insufficient as a primary intervention for a patient in acute respiratory failure with a pH of 7.28. The patient's primary problem is hypoventilation leading to CO₂ retention, which requires immediate ventilatory support, not just coaching.

Option 2: Position the patient in high Fowler's position and administer low-flow oxygen.

This is the most appropriate initial nursing action. High Fowler's position optimizes lung expansion by reducing pressure from the abdominal organs on the diaphragm. The critical component here is the administration of low-flow oxygen. In COPD patients with chronic CO₂ retention, the respiratory drive can shift from a normal response to high CO₂ levels to a reliance on hypoxic drive. Administering high concentrations of oxygen can suppress this drive, leading to further hypoventilation and worsening hypercapnia. The goal is to correct hypoxemia (PaO₂ of 70 mmHg is low) without eliminating the hypoxic drive, typically targeting an SpO₂ of 88-92%. This strategy supports the patient while preparing for or initiating physician-ordered non-invasive ventilation (NIV), which is the first-line ventilatory strategy for this condition [1].

Option 3: Prepare for immediate intubation and mechanical ventilation.

This is premature as a first-line intervention. According to the provided evidence, non-invasive ventilation (NIV) is the current first-line ventilatory strategy for hypercapnic ARF in COPD exacerbation [1]. Intubation is reserved for patients who fail NIV, have contraindications to NIV, or present with severe instability such as respiratory arrest. Jumping directly to an invasive procedure bypasses the standard, less invasive standard of care.

Option 4: Administer sodium bicarbonate as ordered by the physician.

This is contraindicated in respiratory acidosis. The problem is not a lack of bicarbonate (HCO₃⁻ is normal at 26 mEq/L) but an excess of CO₂. Administering sodium bicarbonate would provide a temporary buffering effect, but it generates more CO₂ as a byproduct, paradoxically worsening the underlying respiratory acidosis. The definitive treatment is to improve ventilation and blow off the excess CO₂.

Pathophysiology and Clinical Rationale

In an acute COPD exacerbation, worsening airflow limitation and increased dead space ventilation lead to a rapid rise in PaCO₂, overwhelming the kidneys' ability to compensate by retaining bicarbonate over several days. The resulting acute respiratory acidosis (low pH, high PaCO₂, normal HCO₃⁻) depresses the central nervous system and can progress to life-threatening complications. The immediate nursing priority is to support oxygenation and ventilation safely. High Fowler's position and carefully titrated low-flow oxygen address the hypoxemia while mitigating the risk of abolishing the hypoxic drive, a key safety consideration in this population. This intervention serves as a bridge to the definitive first-line therapy, which is NIV, as highlighted in the review of hypercapnic ARF management [1].References (research sources)

- [1]Management of hypercapnic acute respiratory failure with high-flow nasal cannula therapy: A narrative review.Research articleGirault C, Artaud-Macari E, Declercq PL, Frat JP, Ricard JD, Thille AW, Béduneau G. (2026) · DOI: 10.1016/j.aicoj.2026.100053

## 임상 시나리오

Clinical Guide: Acute Hypercapnic Respiratory Failure in COPD

ABG Interpretation

- **pH 7.28**: Acidosis (normal 7.35-7.45).

- **PaCO2 55 mmHg**: Elevated (normal 35-45), indicating a respiratory source.

- **HCO3- 26 mEq/L**: Normal (22-26), suggesting no metabolic compensation (acute process).

- **Diagnosis**: Acute uncompensated respiratory acidosis.

Immediate Nursing Interventions

- **Positioning**: Place the patient in High Fowler's or tripod position to maximize chest expansion and diaphragmatic excursion.

- **Oxygen Therapy**: Initiate low-flow oxygen (e.g., 1-2 L/min via nasal cannula) to target SpO2 88-92%. Titrate carefully to avoid suppressing the hypoxic drive and worsening hypercapnia.

- **Assessment**: Continuously monitor respiratory rate, depth, breath sounds, SpO2, and level of consciousness.

- **Medication**: Administer prescribed bronchodilators and corticosteroids, typically via nebulizer or inhaler.

Safety Considerations

- **Avoid High-Flow O2**: High concentrations can lead to oxygen-induced hypercapnia in chronic CO2 retainers by blunting the hypoxic drive and causing V/Q mismatch.

- **Escalation**: If the patient deteriorates (worsening ABG, decreased consciousness, respiratory muscle fatigue), prepare for non-invasive ventilation (BiPAP) or intubation.

- **Do Not Give NaHCO3**: Bicarbonate is contraindicated for respiratory acidosis as it does not address the underlying hypoventilation and may cause paradoxical intracellular acidosis.

## 핵심 개념

- **Respiratory Acidosis** — A condition of decreased pH and elevated PaCO2 caused by alveolar hypoventilation, leading to CO2 retention.
- **Hypoxic Drive** — A respiratory drive mechanism in some chronic CO2 retainers where breathing is stimulated primarily by low PaO2 rather than high PaCO2.
- **High Fowler's Position** — An upright seated position with the head of the bed elevated 60 to 90 degrees to maximize lung expansion and diaphragmatic excursion.
- **Hypercapnia** — An abnormally elevated level of carbon dioxide (PaCO2) in the arterial blood, typically >45 mmHg.
- **Acute Exacerbation of COPD** — A sudden worsening of respiratory symptoms in a COPD patient, often triggered by infection, leading to acute respiratory failure.

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