A nurse is caring for a client with pneumonia who is on mechanical ventilation and exhibits a respiratory rate of 34 breaths per minute. The client's ABG results show a pH of 7.5, PaCO2 of 28 mm Hg, and HCO3 of 22 mEq/L. Which nursing action should be prioritized?

The arterial blood gas (ABG) results indicate respiratory alkalosis, characterized by a high pH (7.5) and a low PaCO2 (28 mm Hg), while the bicarbonate remains within the normal range. In a client with pneumonia on mechanical ventilation, a respiratory rate of 34 breaths per minute suggests hyperventilation. Respiratory alkalosis occurs when excessive ventilation causes increased elimination of carbon dioxide from the body, leading to a rise in blood pH. In mechanically ventilated clients, this often results from hyperventilation due to excessive ventilator settings or patient distress. Rationale: A. Administering an anxiolytic may be helpful if anxiety is contributing to hyperventilation, but in this case the client is on mechanical ventilation, making ventilator settings the more direct and immediate cause to address. Priority should be given to correcting the mechanical source of excessive ventilation first. Sedation without adjusting ventilation may delay proper correction of the alkalosis. B. Administering sodium bicarbonate is inappropriate because sodium bicarbonate is used to treat metabolic acidosis, not respiratory alkalosis. This client already has an elevated pH of 7.5, indicating alkalemia, and giving bicarbonate would worsen the imbalance. The low PaCO2 confirms that the primary problem is excessive carbon dioxide loss rather than bicarbonate deficiency. C. Increasing oxygen concentration is not the priority because the ABG findings indicate a ventilation problem rather than an oxygenation problem. The major abnormality is low PaCO2 caused by excessive respiratory rate, not evidence of hypoxemia. Raising oxygen concentration will not correct respiratory alkalosis and may expose the client to unnecessary oxygen-related complications. D. Decreasing the respiratory rate of the mechanical ventilator is the priority intervention because it directly addresses the cause of respiratory alkalosis. A respiratory rate of 34 breaths per minute causes excessive carbon dioxide elimination, resulting in PaCO2 of 28 mm Hg and elevated pH. Lowering the ventilator rate helps retain carbon dioxide and gradually restores normal acid-base balance.