n, pl  -tho*rax*es  or  -tho*ra*ces   1  :  an abnormal state characterized by the presence of gas (as air) in the pleural cavity - see TENSION PNEUMOTHORAX  - compare OLEOTHORAX   2  :  the induction of pneumothorax as a therapeutic measure to collapse the lung or as an aid to roentgenography .
 
   
 
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