Which of the following ABG abnormalities should the nurse anticipate in a client with advanced COPD?
A. Increased PaCO2
B. Increased PaO2
C. Increased pH
D. Increased oxygen saturation
Correct Answer: A. Increased PaCO2
As COPD progresses, the client typically develops increased PaCO2 levels and decreased PaO2 levels. This results in decreased pH and decreased oxygen saturation. These changes are the result of air trapping and hypoventilation. Arterial blood gas (ABG) analysis provides the best clues as to acuteness and severity of disease exacerbation.
Option B: Patients with mild COPD have mild to moderate hypoxemia without hypercapnia. As the disease progresses, hypoxemia worsens and hypercapnia may develop, with the latter commonly being observed as the FEV1 falls below 1 L/s or 30% of the predicted value. Lung mechanics and gas exchange worsen during acute exacerbations.
Option C: In general, renal compensation occurs even in chronic CO2 retainers (ie, bronchitis); thus, pH usually is near normal. Generally, consider any pH below 7.3 to be a sign of acute respiratory compromise.
Option D: The compensation to respiratory acidosis consists in a secondary increase in bicarbonate concentration, and the arterial blood gas analysis is characterized by a reduced pH, increased pCO2 (initial variation), and increased bicarbonate levels (compensatory response).
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