what is patient 17944's maximum value of osmolality, urine since 80 months ago?
select max(labevents.valuenum) from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 17944 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'osmolality, urine' ) and datetime(labevents.charttime) >= datetime(current_time,'-80 month')