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Difficulty: MediumPhysiological Adaptation

During morning rounds on a pulmonary step-down unit, a registered nurse reviews the latest laboratory results for a client with a long-standing history of severe chronic obstructive pulmonary disease (COPD). The client is resting quietly in bed, oriented to person, place, and time, and breathing without the use of accessory muscles. The arterial blood gas (ABG) results on room air are as follows:

* pH: 7.36
* PaCO2: 58 mm Hg
* HCO3: 32 mEq/L
* PaO2: 63 mm Hg

Which of the following is the most appropriate action for the nurse to take based on these clinical findings?

  1. Continue to closely monitor the client's vital signs and respiratory status.Answer
  2. B
    Initiate oxygen therapy via a non-rebreather mask at 12 liters per minute.
  3. C
    Prepare to administer a continuous intravenous infusion of sodium bicarbonate.
  4. D
    Activate the rapid response team to evaluate the client for impending respiratory failure.

Answer

The most appropriate action is to continue to closely monitor the client's vital signs and respiratory status, as the assessment and laboratory findings indicate a stable, chronic baseline.
The client's ABG results demonstrate fully compensated respiratory acidosis, which is an expected baseline finding in severe COPD. The pH is within normal limits (7.35-7.45), while the elevated PaCO2 reflects chronic CO2 retention and the elevated HCO3 reflects the kidneys' metabolic compensation. Combined with a reassuring physical assessment (resting quietly, oriented, absent accessory muscle use), these findings do not indicate an acute deterioration. Therefore, maintaining current interventions and continuing to monitor the client is the safest and most appropriate action.

Step-by-Step Solution

1
Analyze the arterial blood gas (ABG) pH value.
The pH is 7.36, which falls within the normal physiological range of 7.35 to 7.45.
Determining if the overall acid-base balance is normal, acidotic, or alkalotic is the first step in ABG interpretation.
2
Evaluate the PaCO2 and HCO3 values to determine the primary abnormality and any physiological compensation.
The PaCO2 is elevated at 58 mm Hg (normal 35-45 mm Hg), indicating respiratory acidosis. The HCO3 is correspondingly elevated at 32 mEq/L (normal 22-26 mEq/L), indicating renal compensation. Because the pH remains normal, this constitutes fully compensated respiratory acidosis.
Comparing CO2 and HCO3 to the pH identifies both the source of the acid-base imbalance and the body's compensatory mechanisms.
3
Assess the PaO2 value in the context of the client's medical history.
The PaO2 is 63 mm Hg. In severe COPD, a mildly to moderately low PaO2 is a common baseline finding due to chronic hypoxemia.
Understanding the client's chronic disease state is essential for determining if a physiological value represents an acute threat or a chronic adaptation.
4
Correlate the ABG results with the clinical presentation to formulate a nursing priority action.
The client is resting quietly, fully oriented, and breathing without accessory muscle use. The ABG values reflect a stable, fully compensated state.
Treating the client based on their clinical presentation in conjunction with laboratory data prevents unnecessary and potentially harmful overtreatment.

Key Concept

Fully Compensated Respiratory Acidosis in COPD
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Topics

Physiological Adaptation

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