A nurse is assessing a client. Which of the following findings should the nurse identify as an indication of respiratory failure?

Rationale: A. Agitation: Agitation is an early neurologic manifestation of hypoxemia and hypercapnia associated with respiratory failure. Inadequate gas exchange leads to decreased oxygen delivery to cerebral tissue, resulting in restlessness, confusion, and behavioral changes. Rising carbon dioxide levels can also alter mental status due to respiratory acidosis and cerebral vasodilation. B. Friction rub: A pleural friction rub is a grating sound heard on auscultation when inflamed pleural surfaces rub together during respiration. It is commonly associated with pleuritis or pulmonary inflammation rather than impaired gas exchange. While it indicates a pulmonary condition, it does not specifically signify respiratory failure or inadequate oxygenation. C. Xerostomia: Xerostomia refers to dry mouth and is often related to dehydration, medication side effects, or reduced salivary secretion. It does not reflect impaired ventilation or oxygenation status. This finding has no direct correlation with arterial blood gas abnormalities or respiratory insufficiency. D. Decreased end-tidal CO2: End-tidal carbon dioxide (ETCO2) reflects the amount of carbon dioxide exhaled at the end of expiration and helps assess ventilation. Respiratory failure due to hypoventilation results in elevated, not decreased, CO2 levels. A decreased ETCO2 is more commonly seen with hyperventilation, poor perfusion, or equipment-related issues.