instruction: what is the number of patients who underwent mechanical ventilation in 2101 during the same hospital visit after diagnosis of change in mental status?
response: SELECT COUNT(DISTINCT t1.uniquepid) FROM (SELECT patient.uniquepid, diagnosis.diagnosistime, patient.patienthealthsystemstayid FROM diagnosis JOIN patient ON diagnosis.patientunitstayid = patient.patientunitstayid WHERE diagnosis.diagnosisname = 'change in mental status' AND STRFTIME('%y', diagnosis.diagnosistime) = '2101') AS t1 JOIN (SELECT patient.uniquepid, treatment.treatmenttime, patient.patienthealthsystemstayid FROM treatment JOIN patient ON treatment.patientunitstayid = patient.patientunitstayid WHERE treatment.treatmentname = 'mechanical ventilation' AND STRFTIME('%y', treatment.treatmenttime) = '2101') AS t2 WHERE t1.diagnosistime < t2.treatmenttime AND t1.patienthealthsystemstayid = t2.patienthealthsystemstayid