Which sign would indicate an immediate need for intervention in a patient with FBAO?

In the context of a foreign body airway obstruction (FBAO), the inability to speak is a critical sign that indicates a severe obstruction, which necessitates immediate intervention. When a person is unable to speak, it suggests that the airway is significantly compromised, and they may be progressing towards complete obstruction. This situation can lead to inadequate oxygenation and, if not resolved quickly, may result in respiratory failure or death.

The other options represent varying levels of airway compromise or discomfort but do not indicate the same urgency for intervention. A soft cough suggests that some air is still moving, and the person has at least some ability to clear the obstruction, though monitoring is still necessary. A dry throat sensation may indicate discomfort but does not necessarily signal a life-threatening obstruction. Normal breathing sounds imply that airway patency is intact, which would not require immediate intervention.

Thus, the inability to speak is a clear and immediate indicator of a life-threatening situation requiring urgent action, such as performing the Heimlich maneuver or calling for emergency medical assistance.