instruction: what is patient 004-32341's last sao2 on this month/09?
response: SELECT vitalperiodic.sao2 FROM vitalperiodic WHERE vitalperiodic.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '004-32341')) AND NOT vitalperiodic.sao2 IS NULL AND DATETIME(vitalperiodic.observationtime, 'start of month') = DATETIME(CURRENT_TIME(), 'start of month', '-0 month') AND STRFTIME('%d', vitalperiodic.observationtime) = '09' ORDER BY vitalperiodic.observationtime DESC LIMIT 1