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Difficulty: MediumPhysiological Adaptation

A nurse is caring for a client who was admitted to the emergency department with a severe asthma exacerbation. Upon admission, the client was anxious, had a respiratory rate of 34 breaths/minute, and exhibited loud, bilateral expiratory wheezing. Reassessment two hours later reveals the client is lethargic, has a respiratory rate of 12 breaths/minute, and lung sounds are significantly diminished. Which of the following arterial blood gas (ABG) results is most consistent with the client's current presentation?

  1. pH 7.26, PaCO2 65 mm Hg, PaO2 58 mm Hg, HCO3- 25 mEq/LAnswer
  2. B
    pH 7.50, PaCO2 29 mm Hg, PaO2 72 mm Hg, HCO3- 22 mEq/L
  3. C
    pH 7.39, PaCO2 39 mm Hg, PaO2 96 mm Hg, HCO3- 24 mEq/L
  4. D
    pH 7.32, PaCO2 35 mm Hg, PaO2 85 mm Hg, HCO3- 16 mEq/L

Answer

The correct answer is the ABG result showing pH 7.26, PaCO2 65 mm Hg, PaO2 58 mm Hg, and HCO3- 25 mEq/L.
The client's progression from tachypnea and loud wheezing to lethargy, a decreased respiratory rate, and diminished lung sounds indicates respiratory muscle fatigue and impending respiratory failure (often termed a 'silent chest'). As the client loses the ability to effectively ventilate, carbon dioxide is retained, leading to uncompensated respiratory acidosis and worsening hypoxemia. The result showing a low pH (7.26), elevated PaCO2 (65 mm Hg), and low PaO2 (58 mm Hg) with a normal HCO3- accurately reflects this acute physiological decompensation.

Step-by-Step Solution

1
Analyze the client's initial presentation versus the current presentation.
The client progressed from anxious and tachypneic with loud wheezing to lethargic and bradypneic with diminished lung sounds.
Comparing baseline to current findings identifies the clinical trajectory of the client's respiratory status.
2
Interpret the clinical significance of the current findings.
Lethargy, a decreased respiratory rate of 12 breaths/minute, and diminished lung sounds (a 'silent chest') indicate severe respiratory muscle fatigue and impending respiratory failure.
When a client with severe asthma becomes exhausted, they can no longer maintain the work of breathing necessary to move air through highly constricted airways.
3
Correlate the clinical status with the expected arterial blood gas (ABG) changes.
Ineffective ventilation leads to carbon dioxide retention (PaCO2 > 45 mm Hg), resulting in respiratory acidosis (pH < 7.35) and worsening hypoxemia (PaO2 < 80 mm Hg).
A high PaCO2 and low pH perfectly reflect the physiological decompensation of a failing respiratory system in acute asthma.

Key Concept

Impending respiratory failure in severe asthma presents clinically as lethargy, decreased respiratory rate, and 'silent chest', and physiologically as respiratory acidosis with hypercapnia.
Estimated Time:1m 30s
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Topics

Physiological Adaptation

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