Air can enter an elephants body through three entrances, its mouth, trunk and forehead (through internal nares).
Elephant lungs have a unique lung physiology: they don't have a pleural space between the lung and the chest wall, In elephants,
the pleural cavity is filled with connective tissue.
In 1681, a scientist in Dublin, Ireland, conducted an autopsy on an elephant that had died in a fire and wrote that the elephant's lungs were different
from those of any other four-legged animal he'd ever seen.
Their lungs are attached directly to the diaphragm and chest wall, allowing them to create much greater "vacuum pressure"
for sucking water through their long trunks, while drinking.
This might be an indication that elephants evolved from aquatic mammals like manatees. (John B. West et.al. 2002)
During tranquilization, elephants must lay on the side in order to be able to breath. If they lie in sternum recumbancy to long time, they will die.
West, John B. 2002. "Why Doesn't the Elephant Have A Pleural Space," and "Snorkel Breathing in the Elephant Explains the Unique Anatomy of the Pleura."
University of California, San Diego's Department of Medicine.