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: Caffeine - induced changes in diastolic BP were 2 to 3 times larger in borderline subjects than in controls ( + 8 . 4 vs + 3 . 8 mm Hg , p < 0 . 0001 ) , and were attributable to larger changes in impedance - derived measures of systemic vascular resistance ( + 135 vs + 45 dynes . s . cm - 5 , p < 0 . 004 ) .
### Output Text:
<span class="chemical">Caffeine</span> - induced changes in diastolic BP were 2 to 3 times larger in borderline subjects than in controls ( + 8 . 4 vs + 3 . 8 mm Hg , p < 0 . 0001 ) , and were attributable to larger changes in impedance - derived measures of systemic vascular resistance ( + 135 vs + 45 dynes . s . cm - 5 , p < 0 . 004 ) . 