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: Dex increased systolic blood pressure ( SBP ) from 109 + / - 1 . 8 to 135 + / - 0 . 6 mmHg and plasma superoxide ( 5711 + / - 284 . 9 saline , 7931 + / - 392 . 8 U / ml dex , P < 0 . 001 ) .
### Output Text:
<span class="chemical">Dex</span> increased systolic blood pressure ( SBP ) from 109 + / - 1 . 8 to 135 + / - 0 . 6 mmHg and plasma <span class="chemical">superoxide</span> ( 5711 + / - 284 . 9 saline , 7931 + / - 392 . 8 U / ml <span class="chemical">dex</span> , P < 0 . 001 ) . 