Which of the following is the most effective indicator of improved ventilation in a patient with COPD after a nursing intervention?

Rationale: A. An increased respiratory rate may indicate worsening distress, not improved ventilation. B. Decreased use of accessory muscles shows that the patient is breathing more effectively and with less effort, indicating improved ventilation. C. Cyanosis is a sign of hypoxemia, not improvement. D. An increased use of bronchodilators suggests poor symptom control rather than improvement.