Which lung sound indicates an upper airway obstruction?

• A. Stridor
• B. Rales
• C. Wheezing
• D. Rhonchi

Answer: (A)

Stridor is the sound that signals an obstruction in the upper airway, such as the larynx or trachea above the chest. It’s a high-pitched, often harsh or crowing noise heard mainly during inhalation, caused by turbulent airflow as air squeezes through a narrowed area. This narrowing can result from swelling, a foreign body, or other acute airway inflammation (think croup, epiglottitis, or allergic reaction). Because it reflects a blockage above the thoracic inlet, stridor indicates an upper airway issue rather than problems in the deeper lungs.

In contrast, rales (crackles) come from fluid or collapse in the alveolar or interstitial space in the lungs; wheezing is a musical sound from narrowing of smaller airways inside the lungs, typically heard in conditions like asthma or bronchiolitis; rhonchi are coarse sounds from secretions in larger airways and can clear with coughing. These sounds point to problems lower in the airway or in the lung tissue, not an upper airway obstruction.