Lung Auscultation Findings in Croup
In croup, lung auscultation is typically normal or may reveal transmitted upper airway sounds, but the hallmark finding is inspiratory stridor heard over the neck and upper chest, not true lower airway pathology. 1, 2
Key Auscultatory Features
Stridor is the signature sound - this is a high-pitched, harsh inspiratory noise caused by turbulent airflow through the narrowed subglottic trachea, best heard over the trachea and transmitted to the upper chest 2, 3
The lungs themselves are clear - croup is an upper airway obstruction at the laryngeal/subglottic level, not a lower respiratory tract disease, so you should not hear wheezes, crackles, or other adventitious lung sounds 1, 4
Transmitted upper airway sounds may be audible throughout the chest fields, but these represent sound transmission from the obstructed upper airway rather than true pulmonary pathology 2, 3
Critical Diagnostic Distinctions
Inspiratory stridor at rest indicates moderate to severe disease requiring nebulized epinephrine in addition to corticosteroids 1, 5
Biphasic or expiratory stridor suggests more severe obstruction at or below the glottic level and warrants immediate escalation of care 3
A "silent chest" with minimal air movement is an ominous sign indicating severe obstruction and impending respiratory failure, requiring immediate intervention 1, 5
Important Clinical Pitfalls
Do not confuse stridor with wheezing - wheezing is a lower airway sound (expiratory, musical) seen in asthma or bronchiolitis, while stridor is an upper airway sound (inspiratory, harsh) characteristic of croup 1, 3
If you hear true wheezing or crackles, reconsider the diagnosis - this suggests alternative pathology such as asthma, bronchiolitis, pneumonia, or aspiration rather than typical viral croup 1, 4
Absence of stridor does not rule out croup - mild cases may present only with the characteristic barking cough without audible stridor at rest 4, 6