NCLEX-PN® ExaminationPhysiological AdaptationMedium
A client with a history of chronic obstructive pulmonary disease (COPD) is admitted with increased dyspnea and wheezing. Arterial blood gas (ABG) results are pH 7.32, PaCO2 58 mmHg, PaO2 65 mmHg, HCO3 30 mEq/L. The nurse interprets these results as indicating which acid-base imbalance?
- AMetabolic alkalosis with partial respiratory compensation
- BRespiratory alkalosis with partial metabolic compensation
- CRespiratory acidosis with partial metabolic compensation
- DMetabolic acidosis with partial respiratory compensation
Show answer & explanationAnswer & explanation
Correct answer: C. Respiratory acidosis with partial metabolic compensation
The pH of 7.32 indicates acidosis. The elevated PaCO2 (58 mmHg, normal 35-45 mmHg) is the primary cause, indicating a respiratory problem. The elevated HCO3 (30 mEq/L, normal 22-26 mEq/L) indicates that the kidneys are attempting to compensate by retaining bicarbonate, but the compensation is only partial because the pH is still acidic.
Why the other options are wrong
- A. Metabolic alkalosis would involve a high pH and high HCO3.
- B. Respiratory alkalosis would involve a high pH and low PaCO2.
- D. Metabolic acidosis would involve a low pH and low HCO3. This client has high PaCO2 and HCO3.
Respiratory Acidosis with Compensation
Respiratory acidosis is characterized by a low pH and high PaCO2, often due to hypoventilation. Partial metabolic compensation occurs when the kidneys retain bicarbonate, raising HCO3, to buffer the acidosis.
- Low pH, high PaCO2 are primary indicators.
- High HCO3 indicates renal compensation.
- Common in COPD exacerbations due to impaired gas exchange.
Memory trick: ROMA: Respiratory Opposite, Metabolic Alike