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: A retrospective , case - controlled analysis comparing patients admitted to a medical intensive care unit with severe exacerbations of asthma who received continuously nebulized albuterol ( CNA ) versus intermittent albuterol ( INA ) treatments is reported .
### Output Text:
A retrospective , case - controlled analysis comparing patients admitted to a medical intensive care unit with severe exacerbations of asthma who received continuously nebulized <span class="chemical">albuterol</span> ( CNA ) versus intermittent <span class="chemical">albuterol</span> ( INA ) treatments is reported . 