What sign is most specific for impending respiratory failure?

• A. Tachycardia
• B. Restlessness
• C. Paradoxical breathing and decreased level of consciousness
• D. Increasing cough

Answer: (C)

This item is about recognizing signs that ventilation is deteriorating toward failure. Paradoxical breathing, where the chest wall moves inward during inspiration, signals severe respiratory muscle fatigue and ineffective ventilation. When this is accompanied by a decreased level of consciousness, it strongly points to significant hypoxemia and hypercapnia affecting the brain, meaning respiratory failure is imminent. These two findings together are highly specific for a critical decline in respiratory function.

Other signs like tachycardia or restlessness can occur with many stresses and are not specific to impending failure, and an increasing cough is not a reliable indicator of impending respiratory collapse.