###HUMAN: what is patient 031-22988's monthly maximum level of oxyhemoglobin?, ###ASSISTANT: SELECT MAX(lab.labresult) FROM lab WHERE lab.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '031-22988')) AND lab.labname = 'oxyhemoglobin' GROUP BY STRFTIME('%y-%m', lab.labresulttime)