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: Hypotension induced by ATP was accompanied by significant decreases in mean pulmonary arterial pressure ( p less than 0 . 001 ) , central venous pressure ( p less than 0 . 001 ) , left ventricular end - diastolic pressure ( p less than 0 . 001 ) , total peripheral resistance ( p less than 0 . 001 ) , rate pressure product ( p less than 0 . 001 ) , total body oxygen consumption ( p less than 0 . 05 ) , and heart rate ( p less than 0 . 001 ) ; all these variables returned normal within 30 min after ATP was stopped .
### Output Text:
Hypotension induced by <span class="chemical">ATP</span> was accompanied by significant decreases in mean pulmonary arterial pressure ( p less than 0 . 001 ) , central venous pressure ( p less than 0 . 001 ) , left ventricular end - diastolic pressure ( p less than 0 . 001 ) , total peripheral resistance ( p less than 0 . 001 ) , rate pressure product ( p less than 0 . 001 ) , total body <span class="chemical">oxygen</span> consumption ( p less than 0 . 05 ) , and heart rate ( p less than 0 . 001 ) ; all these variables returned normal within 30 min after <span class="chemical">ATP</span> was stopped . 