Signs of a severe airway obstruction in an infant or child include:

An ineffective cough is a critical indicator of a severe airway obstruction in an infant or child. Coughing is a natural reflex that helps clear the airway of obstructions or irritants. When a child is unable to produce an effective cough, it suggests that the airway may be significantly compromised and that the child is unable to expel air and clear whatever is causing the blockage. This results in the inability to adequately ventilate the lungs, which can lead to respiratory distress and potentially life-threatening situations.

Additionally, recognizing severe airway obstruction relies on identifying that the child's normal protective mechanisms, like coughing, are failing. This ineffectiveness in coughing reflects the severity of the obstruction and necessitates urgent intervention. In comparison, while the other options might indicate some level of respiratory concern, they do not specifically point to a severe obstruction in the same manner as an ineffective cough does.