has ever been the sao2 of patient 22897 been ever less than 98.0 until 21 months ago?
select count(*)>0 from chartevents where chartevents.icustay_id in ( select icustays.icustay_id from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 22897 ) ) and chartevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'sao2' and d_items.linksto = 'chartevents' ) and chartevents.valuenum < 98.0 and datetime(chartevents.charttime) <= datetime(current_time,'-21 month')