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: Prehospital care providers who are managing any patient with a syncopal episode that fails to recover within a reasonable time frame should consider the Bezold - Jarisch reflex as the cause and manage the patient accordingly .
### Output Text:
Prehospital care providers who are managing any patient with a syncopal episode that fails to recover within a reasonable time frame should consider the Bezold - Jarisch reflex as the cause and manage the patient accordingly . 