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Difficulty: MediumPhysiological Adaptation

A nurse evaluates a client experiencing a severe asthma exacerbation. Upon admission, the client was visibly struggling to breathe with a respiratory rate of 38 breaths per minute, and an initial arterial blood gas (ABG) analysis showed a PaCO2 of 28 mm Hg. Two hours later, the client's respiratory rate has decreased to 16 breaths per minute, and breath sounds are significantly diminished bilaterally. A repeat ABG reveals a pH of 7.36, PaCO2 of 43 mm Hg, PaO2 of 59 mm Hg, and HCO3 of 23 mEq/L. Which of the following is the most appropriate action for the nurse to take?

  1. A
    Document the stabilization of the client's respiratory rate and ABG values.
  2. B
    Administer a prescribed as-needed nebulized albuterol treatment.
  3. Activate the rapid response team and gather equipment for advanced airway management.Answer
  4. D
    Assist the client into an orthopneic position and encourage deep breathing.

Answer

Activate the rapid response team and gather equipment for advanced airway management.
In a severe asthma exacerbation, clients initially hyperventilate, blowing off CO2 and causing respiratory alkalosis (low PaCO2). If the client tires, the respiratory rate drops, and PaCO2 begins to rise back into the 'normal' range (35-45 mm Hg). In the context of diminished breath sounds (a 'silent chest') and persistent hypoxemia, this 'pseudonormalization' of PaCO2 is a critical sign of respiratory muscle fatigue and impending respiratory failure. Immediate intervention with advanced airway management is required.

Step-by-Step Solution

1
Analyze the client's initial presentation.
The client presented with hyperventilation (respiratory rate of 38/min) causing a rapid blow-off of carbon dioxide (PaCO2 of 28 mm Hg), which is an expected early compensatory mechanism in severe asthma.
Establishing the baseline helps identify subsequent clinical deterioration or improvement.
2
Evaluate the clinical changes observed after two hours.
The respiratory rate has decreased to a 'normal' 16/min, and breath sounds are now significantly diminished (silent chest).
Clinical assessment often reveals deterioration before laboratory values confirm it. A 'silent chest' indicates severe airflow obstruction.
3
Interpret the repeat arterial blood gas (ABG) results in the context of the clinical assessment.
The PaCO2 has risen to 43 mm Hg (within the normal range of 35-45 mm Hg), and hypoxemia persists (PaO2 59 mm Hg).
ABG values must always be interpreted alongside the client's physical presentation. A normal PaCO2 is an alarming finding in an actively wheezing or severely asthmatic client.
4
Determine the physiological state and the priority nursing intervention.
The normalization of PaCO2 (pseudonormalization) combined with decreased respiratory effort signifies severe respiratory muscle fatigue and impending respiratory arrest, requiring immediate rapid response and intubation.
Delaying advanced airway management in the presence of impending ventilatory failure will lead to cardiac arrest.

Key Concept

Impending Respiratory Failure and Pseudonormalization of ABGs
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Topics

Physiological Adaptation

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