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: As compared with controls , fluoxetine exposure resulted in fetal pulmonary hypertension as evidenced by an increase in the weight ratio of the right ventricle to the left ventricle plus septum ( P = 0 . 02 ) and by an increase in pulmonary arterial medial thickness ( P < 0 . 01 ) .
### Output Text:
As compared with controls , <span class="chemical">fluoxetine</span> exposure resulted in fetal pulmonary hypertension as evidenced by an increase in the weight ratio of the right ventricle to the left ventricle plus septum ( P = 0 . 02 ) and by an increase in pulmonary arterial medial thickness ( P < 0 . 01 ) . 