In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: On the other hand , BNP did not increase in the patients without heart failure given DNR , even at more than 700 mg / m ( 2 ) .
### Output Text:
On the other hand , BNP did not increase in the patients without heart failure given <span class="chemical">DNR</span> , even at more than 700 mg / m ( 2 ) . 