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: It is concluded that increases in the SPV and the delta down are characteristic of a hypotensive state due to a predominant decrease in preload .
### Output Text:
It is concluded that increases in the SPV and the delta down are characteristic of a hypotensive state due to a predominant decrease in preload . 