what are patient 14502's changes in arterial bp mean last measured on the last intensive care unit visit compared to the second to last value measured on the last intensive care unit 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 = 14502 ) 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 mean' and d_items.linksto = 'chartevents' ) order by chartevents.charttime desc limit 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 = 14502 ) 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 mean' and d_items.linksto = 'chartevents' ) order by chartevents.charttime desc limit 1 offset 1 )