Which finding would indicate imminent respiratory failure in a patient with asthma?

The absence of wheezes in a patient with asthma often indicates a worsening condition and can signal imminent respiratory failure. Wheezing is a common sound associated with airflow obstruction in asthmatic patients; therefore, when wheezing diminishes or disappears, it suggests that the airflow has been severely compromised — possibly indicating that the patient is reaching a critical point of respiratory distress where sufficient airflow is no longer achievable.

In a typical asthma exacerbation, wheezing reflects the presence of bronchoconstriction and inflammation. If wheezing ceases, it may mean that the patient is unable to maintain adequate airflow due to severe airway constriction or exhaustion, leading to respiratory failure. This is contrasted with other options where increased wheezing indicates ongoing obstruction and activity in the lungs, which while concerning, does not inherently signify imminent respiratory failure. Improved breath sounds might suggest that treatment is effective or that obstruction has resolved, while normal blood pCO2 does not suggest the immediate danger of respiratory failure, as elevated levels might indicate hypoventilation or inadequate gas exchange.