Pneumothorax

Lung ultrasound has high sensitivity (88%) and specificity (100%) for pneumothorax detection, with good correlation with CT scan. Lung ultrasound can be performed with any ultrasound machine and probe; however, a high-frequency probe allows the best visualization of the pleural line for pneumothorax detection. A complete examination includes 12 zones (2 anterior, 2 lateral, and 2 posterior per hemithorax); free air collection can be ruled out with a simplified approach focused on anterior fields, in particular in emergency situations. The presence of lung sliding/seashore sign, lung pulse, B-lines, or real images (consolidations/effusions) rules out pneumothorax with 100% negative predictive value. The absence of lung sliding with A-lines, confirmed by the stratosphere sign, strongly suggests pneumothorax, with high sensitivity and moderate context-related specificity. This can be mimicked by clinical situations limiting the lung sliding (pleural bullae and emphysema, hyperinflation). To confirm pneumothorax with 100% positive predictive value, it is essential to visualize the lung point, contact point between air collection and collapsed lung. Mapping the lung point on the thorax allows semi-quantification of the pneumothorax and guides thoracic drainage. In case of complete collapse, the lung point cannot be visualized. Lung ultrasound limitations include thoracic dressing, subcutaneous emphysema, and adequate training.