Which of the following may represent an upper airway obstruction?

Stridor is the sound produced by turbulent airflow through a partially obstructed upper airway. It is a classic sign of upper airway obstruction. While an elongated expiratory phase may indicate lower airway obstruction, stridor specifically points to an upper airway issue. Retractions are also often seen in upper airway obstruction due to the increased effort of breathing. Expiratory wheezing, on the other hand, is more indicative of lower airway conditions such as asthma or chronic obstructive pulmonary disease (COPD).