how much changes has patient 30235's arterial bp [systolic] second measured on the last icu visit compared to the value first measured on the last icu visit?
select ( select chartevents.valuenum 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 = 30235 ) and icustays.outtime is not null order by icustays.intime desc limit 1 ) and chartevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'arterial bp [systolic]' and d_items.linksto = 'chartevents' ) order by chartevents.charttime asc limit 1 offset 1 ) - ( select chartevents.valuenum 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 = 30235 ) and icustays.outtime is not null order by icustays.intime desc limit 1 ) and chartevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'arterial bp [systolic]' and d_items.linksto = 'chartevents' ) order by chartevents.charttime asc limit 1 )