what is the yearly minimum amount of theophylline of patient 27172 since 5 years ago?
select min(labevents.valuenum) from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 27172 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'theophylline' ) and datetime(labevents.charttime) >= datetime(current_time,'-5 year') group by strftime('%y',labevents.charttime)