A child with a suspected airway obstruction is brought to the emergency room. The parent reports a fever last night. He produces a harsh, strident sound on inspiration (stridor). Where is the obstruction likely to be located based on this information?

Choice A reason: Obstruction in the pharynx may cause snoring or gurgling sounds, but it typically does not produce stridor. The pharynx is part of the upper airway, and while swelling here can contribute to airway compromise, stridor is more specifically associated with structures below the pharynx. Choice B reason: Stridor is a high-pitched, harsh sound heard during inspiration and is most commonly associated with obstruction at the level of the larynx. Conditions such as croup, epiglottitis, or laryngeal edema can cause narrowing of the airway at this level, leading to turbulent airflow and stridor. The presence of fever and stridor strongly suggests inflammation or infection affecting the larynx. Choice C reason: Bronchiolar obstruction typically causes wheezing, not stridor. Wheezing is heard during expiration and is associated with lower airway conditions such as bronchiolitis or asthma. It reflects small airway narrowing, not upper airway obstruction. Choice D reason: Obstruction in the lower trachea may cause more generalized respiratory distress and possibly wheezing or diminished breath sounds, but it is not the typical source of stridor. Stridor is generated in the upper airway, particularly the larynx.