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Difficulty: MediumPhysiological Adaptation

A nurse is caring for a client admitted with a severe acute asthma exacerbation. Upon admission, the client was agitated with a respiratory rate of 34 breaths/min. Initial arterial blood gas (ABG) results demonstrated a pH of 7.52, a PaCO2 of 26 mm Hg, and a PaO2 of 72 mm Hg. Two hours later, the client appears lethargic, the respiratory rate has decreased to 14 breaths/min, and breath sounds are significantly diminished with absent wheezing. A repeat ABG reveals a pH of 7.37, a PaCO2 of 42 mm Hg, and a PaO2 of 64 mm Hg. Which of the following is the priority nursing action?

  1. Prepare the client for immediate endotracheal intubation and mechanical ventilation.Answer
  2. B
    Document the improvement in the client's acid-base balance and respiratory status.
  3. C
    Administer a prescribed continuous intravenous infusion of a corticosteroid.
  4. D
    Increase the supplemental oxygen delivery via a non-rebreather mask.

Answer

The correct action is to prepare the client for immediate endotracheal intubation and mechanical ventilation.
The client is exhibiting signs of impending respiratory arrest. The transition from respiratory alkalosis (low PaCO2 driven by hyperventilation) to a seemingly 'normal' PaCO2, combined with lethargy, a decreased respiratory rate, and a 'silent chest' (diminished breath sounds with absent wheezing), indicates severe respiratory muscle fatigue. The client can no longer maintain adequate ventilation, making immediate airway management and mechanical support the highest priority.

Step-by-Step Solution

1
Analyze the client's initial presentation against the current presentation.
Initially, the client was hyperventilating (respiratory alkalosis). Currently, the client is lethargic with a decreased respiratory rate and absent wheezing (silent chest).
Tracking clinical trends is essential for recognizing sudden deterioration in acute respiratory conditions.
2
Interpret the physiological meaning of the repeat ABG results in the context of the clinical changes.
The PaCO2 has risen from 26 mm Hg to 42 mm Hg. In a tired asthmatic, a 'normal' PaCO2 indicates pseudonormalization; the client is no longer able to maintain the work of breathing necessary to overcome the airway resistance.
An isolated ABG value must always be interpreted alongside the clinical assessment to avoid diagnostic errors.
3
Determine the highest priority nursing intervention.
The client requires immediate artificial airway placement and mechanical ventilation.
The combination of lethargy, silent chest, and rising PaCO2 is a classic presentation of impending respiratory arrest, requiring emergency life support.

Key Concept

Impending respiratory failure and pseudonormalization of ABGs in severe asthma
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Topics

Physiological Adaptation

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