Answers to Illuminations

Arch Dis Child Educ Pract Ed 2010;95:204. doi:10.1136/adc.2010.197335a 204 ANSWERS From questions on page 196 1. The answer is D: lobar collapse secondary to mucus plugging. The endotracheal tube (ETT) is in a satisfactory position but the left lower lobe (LLL) is collapsed and can be seen as a ‘triangular’ shaped density behind the heart (dotted line fi gure 3 indicates the hypotenuse of the triangle). Because the LLL is no longer aerated and has effectively become solid, there is loss of the normal outline of the left hemidiaphragm, which is usually seen because of its interface with the typically air-fi lled LLL; this is known as the silhouette sign. Absence of normal silhouettes of chest structures helps to identify pathology such as lobar collapse and also to localise masses. The other sign that there is pathology in the left hemithorax in this patient is related to the loss of overall volume in the left lung. Not only does the left hemithorax look smaller than the right, but owing to mediastinal shift to the left side, less of the right heart border is seen to the right of the spine in the lower mediastinum (arrows fi gure 3). Mucus plugging occurs more commonly in patients with cystic fi brosis, infection or asthma and also in those with thick secretions caused by relative dehydration. Patients with head injuries are often initially fl uid restricted to minimise the likelihood of cerebral oedema, which could be a contributing factor in this patient. Decreased mobility, dependent position, drying effects of the inspired gases and lack of coughing in ventilated patients also makes them more prone to this complication. The next most appropriate course of action would be suction, patient repositioning and chest physiotherapy if the patient is stable enough. 2. The answer is H: displaced ETT. The ETT tip (arrowhead fi gure 4) has entered the bronchus intermedius so that only the right middle and lower lobes are aerated. There is collapse of the left lung and right upper lobe, which are all opacifi ed. The whole left hemithorax is smaller than the right (note that the ribs look closer together than on the right side) owing to volume loss and the normal silhouettes of the left hemidiaphragm and left heart border are lost. The collapsed right upper lobe is seen as a triangular density near the lung apex, with a slightly concave lower border. This patient also has a mediastinal drain in situ (long arrow fi gure 4) and epicardial pacing wires (short arrows fi gure 4). The ETT needs repositioning or replacing.