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: Twelve asthmatic patients ( FEV1 , 81 + / - 4 % predicted ) , requiring only occasional inhaled beta - agonists as their sole therapy , were given a 14 - day treatment with high dose inhaled salbutamol ( HDS ) , 4 , 000 micrograms daily , low dose inhaled salbutamol ( LDS ) , 800 micrograms daily , or placebo ( PI ) by metered - dose inhaler in a double - blind , randomized crossover design .
### Output Text:
Twelve asthmatic patients ( FEV1 , 81 + / - 4 % predicted ) , requiring only occasional inhaled beta - agonists as their sole therapy , were given a 14 - day treatment with high dose inhaled <span class="chemical">salbutamol</span> ( HDS ) , 4 , 000 micrograms daily , low dose inhaled <span class="chemical">salbutamol</span> ( LDS ) , 800 micrograms daily , or placebo ( PI ) by metered - dose inhaler in a double - blind , randomized crossover design . 