Pediatric ultrasound of the respiratory tract: Clinical applications

Abstract

Ultrasound for the respiratory tract has been considered useful in various settings of pediatric practice. Important findings include A lines (linear high-echogenicity lines parallel to the pleura), B lines (lines perpendicular to the pleura), and lung sliding (movement of the pleural line in synchrony with breathing).

Appropriate tracheal intubation is confirmed using the snowstorm/bullet signs and the absence of the double tract sign. Pneumothorax is characterized by the disappearance of lung sliding and B lines, and the presence of a lung point.

Even a small amount of pleural fluid is also detectable. Effusion presents as anechoic fluid in the pleural cavity, while in contrast, empyema has higher echogenicity.

Ultrasound further allows for direct observation of pulmonary parenchyma adjacent to the parietal pleura, enabling detection of conditions such as pneumonia, abscess, tumors, and malformations. Indirect findings such as B lines may also be helpful for the diagnosis of bronchiolitis and pulmonary edema. In transient tachypnea of the newborn, delayed absorption of lung fluid is demonstrated as the presence of B lines. In respiratory distress syndrome, an admixture of A lines and B lines is found in mild cases and a white lung pattern without A lines is found in severe cases. These observations can be applied to determination of the need for surfactant administration.