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: RESULTS : The time to first dysrhythmia occurrence , time to 25 % and 50 % reductions in HR , and time to asystole were longer in Group P than the other groups .
### Output Text:
RESULTS : The time to first dysrhythmia occurrence , time to 25 % and 50 % reductions in HR , and time to asystole were longer in Group P than the other groups . 