# A nurse is caring for a patient with pneumonia who presents with fever, tachypnea, and crackles. The patient's arterial blood gas (ABG) results show: pH 7.50, PaCO2 32 mmHg, HCO3- 24 mEq/L, PaO2 70 mmHg. Which assessment finding would be most concerning and require immediate intervention?

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## 문제

A nurse is caring for a patient with pneumonia who presents with fever, tachypnea, and crackles. The patient's arterial blood gas (ABG) results show: pH 7.50, PaCO2 32 mmHg, HCO3- 24 mEq/L, PaO2 70 mmHg. Which assessment finding would be most concerning and require immediate intervention?

## 보기

1. Blood pressure of 150/90 mmHg with mild peripheral edema
2. Respiratory rate of 8 breaths per minute with shallow breathing pattern **✔ 정답**
3. Heart rate of 110 beats per minute with occasional premature ventricular contractions
4. Temperature of 100.2°F (37.9°C) with productive cough

**정답: 2**

## 해설

The ABG shows respiratory alkalosis (pH 7.50, PaCO2 32 mmHg, HCO3- 24 mEq/L). A respiratory rate of 8 with shallow breathing indicates severe hypoventilation and impending respiratory failure, requiring immediate intervention like non-invasive ventilation. Hypertension, tachycardia, and fever are concerning but not immediately life-threatening in this context.

## 심화 해설

ABG Interpretation

The arterial blood gas (ABG) results reveal a primary respiratory alkalosis. The pH is 7.50 (alkalotic), the PaCO2 is 32 mmHg (low, indicating hyperventilation), and the HCO3- is 24 mEq/L (normal, no metabolic compensation yet). This pattern is a classic finding in pneumonia, where hypoxemia and pulmonary irritation drive an increased respiratory rate. The PaO2 of 70 mmHg confirms significant hypoxemia, which is the primary stimulus for the patient's tachypnea.

The most concerning assessment finding is a respiratory rate of 8 breaths per minute with a shallow breathing pattern. This represents a critical and paradoxical decline in the patient's clinical status. The initial ABG shows the patient is compensating for hypoxemia by hyperventilating, which is a protective mechanism to maintain alveolar ventilation. A sudden drop in respiratory rate to a bradypneic level indicates that the patient is no longer able to sustain this compensatory effort. This decompensation is a grave sign, suggesting severe respiratory muscle fatigue, central nervous system depression from worsening hypoxemia, or impending respiratory failure. Without immediate intervention, such as non-invasive or mechanical ventilation, the patient will rapidly progress to acute respiratory acidosis, profound hypoxemia, and cardiac arrest.

While the other options represent clinical findings that require monitoring and management, they do not signal an immediate, life-threatening decompensation in the context of this ABG. A blood pressure of 150/90 mmHg with mild edema may indicate fluid overload or cardiovascular stress, and a heart rate of 110 bpm with occasional PVCs reflects the body's compensatory sympathetic response to hypoxemia and fever. A temperature of 100.2°F (37.9°C) with a productive cough is an expected manifestation of the underlying pneumonia. The transition from tachypnea to bradypnea, however, is a direct threat to the patient's airway and breathing, the highest priorities in the ABC (Airway, Breathing, Circulation) framework. The body's failure to maintain a high respiratory rate in the face of persistent hypoxemia is a pre-terminal indicator that demands immediate escalation of care.

## 임상 시나리오

Clinical Scenario

A patient with pneumonia and ABG-confirmed respiratory alkalosis (pH 7.50, PaCO2 32 mmHg) due to compensatory tachypnea suddenly develops a respiratory rate of 8 breaths per minute with a shallow pattern. This represents a critical decompensation from hyperventilation to hypoventilation, indicating severe respiratory muscle fatigue or central nervous system depression from worsening hypoxemia. This is a pre-arrest sign requiring immediate intervention to prevent acute respiratory failure and cardiac arrest.

Immediate Nursing Actions

- Rapidly assess the patient's level of consciousness, airway patency, and SpO2. Call for emergency assistance and the Rapid Response Team immediately.

- Prepare to initiate bag-valve-mask (BVM) ventilation with 100% oxygen to support ventilation and oxygenation.

- Prepare for immediate transfer to a higher level of care (e.g., ICU) and anticipate the need for non-invasive (BiPAP) or invasive mechanical ventilation.

- Place emergency airway equipment (suction, oral airway, advanced airway cart) at the bedside.

Ongoing Monitoring

- Continuously monitor respiratory rate, depth, and pattern, along with SpO2 and end-tidal CO2 if available.

- Obtain a repeat ABG to evaluate for the development of acute respiratory acidosis (rising PaCO2, falling pH).

- Closely monitor heart rate and rhythm for bradycardia or asystole, which can result from profound hypoxemia.

Clinical Reasoning

The transition from tachypnea to bradypnea is a paradoxical and ominous sign. The patient's initial hyperventilation was a protective response to hypoxemia. The sudden loss of this drive indicates that the respiratory system is failing. This is a time-sensitive emergency where the priority is to take over the work of breathing for the patient to prevent a hypoxic cardiac arrest.

## 핵심 개념

- **Respiratory Alkalosis** — A condition marked by elevated blood pH (>7.45) and low PaCO2 (
- **Bradypnea** — An abnormally slow respiratory rate, which in the context of prior hyperventilation suggests severe fatigue, central nervous system depression, or impending respiratory arrest.
- **Hypoxemic Drive** — The primary stimulus for breathing in patients with chronic CO2 retention, but also a critical compensatory mechanism in acute hypoxemia to increase respiratory rate.
- **Impending Respiratory Failure** — A clinical state where the respiratory muscles can no longer maintain adequate gas exchange, often heralded by a falling respiratory rate and shallow breathing.

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