A. 2nd intercostal space, midclavicular line.
B. 7th intercostal space, midaxillary line.
C. 5th intercostal space, midclavicular line.
D. 5th intercostal space, just lateral to vertebral column.
The condition shown in the x-ray picture above represents tension pneumothorax.
Treatment of tension pneumothorax consists of immediate decompression and is managed initially by rapid insertion of a large bore needle into the second intercostal space in the mid-clavicular line of the affected hemithorax.