when was patient 23475's arterial bp [diastolic] measured for the first time on the first icu visit?
select chartevents.charttime 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 = 23475 ) and icustays.outtime is not null order by icustays.intime asc limit 1 ) and chartevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'arterial bp [diastolic]' and d_items.linksto = 'chartevents' ) order by chartevents.charttime asc limit 1