Presentation
Severe COVID-19 and LLL pneumonia. Deteriorating despite maximal therapy. New ETT inserted in anticipation of imminent proning of the patient.
Patient Data
Armoured ET tube, right-sided IJV catheter and NG tube in good position. Cardiac monitor leads overlie the patient.
Diffuse consolidation less severe in the upper zones/apices with loss of the left hemidiaphragm silhouette. Appearances consistent with left lower lobe pneumonia, on background of COVID-19 pneumonia.
First image: magnified view of the endotracheal tube (ETT).
Second image: arrows and measurement are indicating the relatively radiolucent distal ~2 cm of the ETT which are subtle and could easily be missed.
Case Discussion
This endotracheal tube has a different appearance from the ones that many radiologists are used to seeing. It has a metallic wire implanted in its wall which means it is less likely to collapse and also has increased flexibility. These are called armoured endotracheal tubes (A-ETT), a.k.a. wire-reinforced ETTs, and are used when there is concern about external factors causing collapse/compression of the tube.
Armoured tubes are used in a number of contexts:
- neck and thoracic surgeries (commonest indication)
- difficult intubations, e.g. submental, fiber optic, through a tracheostomy
- ventilation of a patient in the prone position
As these tubes are more flexible they are harder to insert and therefore a stylet is often required to act as a stiffener.
Standard PVC ETTs have a radiopaque stripe extending all the way to the distal tip so that on a chest radiograph the tip is always clearly seen and assessment of their position is relatively straightforward. However armoured tubes have an up to 2 cm plastic-only most distal segment which lacks any radiopaque marker. As can be seen here, this distal part is subtle and can easily be overlooked especially to those not used to looking at armoured tubes on CXR. This increases the risk of a malpositioned tube (e.g. a bronchial insertion) being missed if the metallic portion is just above the carina (not the case here) 1.
Following the recent popularity of proning patients with severe COVID-19 to improve oxygenation, it has led to an increased use of armoured tubes as they are less likely to obstruct in a patient when they are in a prone position. This was the rationale for the insertion of such a tube in this patient.
Unfortunately the internal metal also acts as a weakness, because if they do get bent or the patient bites on the tube then they remain deformed, become unusable, and need to be replaced.
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