A nurse is assisting with the care of a client who has chronic obstructive pulmonary disease (COPD) and is short of breath. When reviewing the client's arterial blood gases (ABGs), which of the following conditions should the nurse anticipate the client to be experiencing?

Chronic obstructive pulmonary disease leads to chronic air trapping and impaired gas exchange. Knowledge of acid-base balance and the physiological relationship between hypoventilation and carbon dioxide retention is essential to interpret ABG results correctly and anticipate the client's metabolic state during respiratory distress. Choice A rationale . Metabolic alkalosis involves a high pH (above 7.45) and high bicarbonate (above 26 mEq/L). It is typically caused by gastric suctioning or vomiting. COPD is a primary respiratory disorder and does not typically result in an initial metabolic alkalotic state. Choice B rationale . Respiratory alkalosis is characterized by a high pH (above 7.45) and low Paco (below 35 mm Hg) due to hyperventilation. Clients with COPD struggle with air trapping and carbon dioxide retention, making this state unlikely unless they are acutely hyperventilating beyond their baseline. Choice C rationale . In COPD, damaged alveoli and narrowed airways cause hypoventilation and CO2 retention. This increases carbonic acid levels, resulting in a low pH (below 7.35) and high Paco (above 45 mm Hg). This acid-base imbalance is a hallmark of chronic respiratory failure. Choice D rationale . Metabolic acidosis is defined by a low pH (below 7.35) and low bicarbonate (below 22 mEq/L). It is commonly caused by renal failure or ketoacidosis. While severe hypoxia can cause lactic acidosis, the primary mechanism in COPD-related distress is respiratory-driven acid accumulation.