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: Supine blood pressure was reduced ( P less than 0 . 01 ) from 170 + / - 20 / 102 + / - 6 mmHg to 153 + / - 19 / 92 + / - 8 , 147 + / - 18 / 88 + / - 7 and 144 + / - 14 / 87 + / - 6 mmHg at 2 , 4 and 6 weeks respectively in evaluable patients .
### Output Text:
Supine blood pressure was reduced ( P less than 0 . 01 ) from 170 + / - 20 / 102 + / - 6 mmHg to 153 + / - 19 / 92 + / - 8 , 147 + / - 18 / 88 + / - 7 and 144 + / - 14 / 87 + / - 6 mmHg at 2 , 4 and 6 weeks respectively in evaluable patients . 