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: The rise in blood pressure became less marked when higher concentrations of sevoflurane or enflurane were administered and the blood pressure at convulsions decreased significantly in 1 . 6 % sevoflurane , and in 0 . 8 % and 1 . 6 % enflurane .
### Output Text:
The rise in blood pressure became less marked when higher concentrations of <span class="chemical">sevoflurane</span> or <span class="chemical">enflurane</span> were administered and the blood pressure at convulsions decreased significantly in 1 . 6 % <span class="chemical">sevoflurane</span> , and in 0 . 8 % and 1 . 6 % <span class="chemical">enflurane</span> . 