Stridor is caused by all except:
**Core Concept**
The presence of stridor, a high-pitched sound heard during inhalation or exhalation, is indicative of upper airway obstruction. This can be caused by various factors, including anatomical abnormalities, foreign bodies, or conditions affecting the larynx, trachea, or bronchi.
**Why the Correct Answer is Right**
Stridor is typically associated with obstruction of the upper airways, which can be caused by conditions such as laryngomalacia, croup, foreign body aspiration, or vocal cord paralysis. The narrowing of the airway lumen leads to turbulent airflow, resulting in the characteristic high-pitched sound. In contrast, lower airway obstruction, such as that caused by bronchial asthma or chronic obstructive pulmonary disease (COPD), typically produces wheezing or rhonchi rather than stridor.
**Why Each Wrong Option is Incorrect**
**Option A:** Anatomical abnormalities such as a tracheal stenosis or a laryngeal web can indeed cause stridor, making this option incorrect.
**Option B:** Foreign body aspiration is a well-known cause of stridor, especially in children, so this option is also incorrect.
**Option C:** Vocal cord paralysis can lead to stridor due to the abnormal movement of the vocal cords, making this option incorrect as well.
**Clinical Pearl / High-Yield Fact**
It's essential to differentiate between stridor and wheezing, as the latter is often associated with lower airway obstruction and may require different management strategies.
**Correct Answer: D**