Lung Ultrasound Allows for Earlier Diagnosis of Bronchiolitis Than Auscultation: an Animal Experiment and Human Case Series

Purpose: Early diagnosis of bronchiolitis in infants allows for risk stratification for central apnea, and, when available, the timely initiation of antiviral treatment. An animal model could demonstrate if earlier diagnosis is possible with ultrasound than with clinical exam. Even if possible, translating this to pediatrics would require observations from undifferentiated human infants.

Methods: We used serial daily clinical and lung ultrasound exams in a bovine calf model (Bos taurus) of respiratory syncytial virus bronchiolitis. Ultrasound and clinical examiners were blinded to each other's findings and the treatments used in 24 calves. Time to diagnosis was compared using Kaplan-Meier curves. A case series of human infants with upper respiratory tract infections, without clinical signs of bronchiolitis, and in whom lung ultrasound was performed, was extracted from hospital records.

Results: In the bovine model, lung ultrasound findings emerged earlier and lasted later than auscultatory findings. Relying on auscultation, 5/24 (21%) of animals were diagnosed by post-inoculation day 5 whereas 24/24 (100%) were diagnosed by ultrasound. We identified seven infants in whom lung ultrasound was used to diagnose bronchiolitis before adventitial lung sounds emerged. Three of these subsequently developed typical clinical findings of bronchiolitis in the hospital. Two had alternative explanations for their abnormal lung ultrasounds (both required surgical intervention). Two were discharged and required no further medical attention.

Conclusion: Lung ultrasound allowed earlier diagnosis of bronchiolitis than clinical exam in the bovine model. In the human case series this was also true, but alternative causes of abnormal ultrasound were frequent.