Is this radiograph better than before?
Yes - the ET tube is safely above the carina and the left lung has re-expanded.
What is the optimal position for an endobronchial tube in adults?
The tip of the ET tube should be at least 2 cm above the carina. This is because the tube can move with neck flexion and extension by approximately 2 cm, and you can't use CXR to gauge head position.
ETT retracted slightly approximately 20 minute interval
Compared with the earlier study, the ETT is now appropriately positioned approximately 2 cm above the carina. Re-expansion of the left lung - the diaphragm is now more visible. The mediastinal shift is also improving (the right cardiac shadow is now to the right of the vertebral bodies).