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

Rationale: A. Friction rub: A friction rub is a sound heard on auscultation, typically due to the rubbing of the pleurae, and is more associated with pleuritis or pleural effusion rather than respiratory failure. B. Xerostomia: Xerostomia, or dry mouth, can be a side effect of medications or dehydration but is not directly an indication of respiratory failure. C. Agitation: Agitation is a common early sign of respiratory failure. As oxygen levels decrease or carbon dioxide levels increase in the bloodstream, the body may respond with restlessness or agitation due to insufficient oxygenation to the brain. D. Decreased end-tidal CO2: A decreased end-tidal CO2 can indicate poor ventilation or respiratory distress, but it is not as specific as agitation in signaling respiratory failure. Agitation is a more direct response to inadequate gas exchange.