instruction: count the number of patients that received non-invasive mech vent procedure in the same hospital encounter after receiving a insert spinal canal cath procedure in 2104.
response: SELECT COUNT(DISTINCT t1.subject_id) FROM (SELECT admissions.subject_id, procedures_icd.charttime, admissions.hadm_id FROM procedures_icd JOIN admissions ON procedures_icd.hadm_id = admissions.hadm_id WHERE procedures_icd.icd9_code = (SELECT d_icd_procedures.icd9_code FROM d_icd_procedures WHERE d_icd_procedures.short_title = 'insert spinal canal cath') AND STRFTIME('%y', procedures_icd.charttime) = '2104') AS t1 JOIN (SELECT admissions.subject_id, procedures_icd.charttime, admissions.hadm_id FROM procedures_icd JOIN admissions ON procedures_icd.hadm_id = admissions.hadm_id WHERE procedures_icd.icd9_code = (SELECT d_icd_procedures.icd9_code FROM d_icd_procedures WHERE d_icd_procedures.short_title = 'non-invasive mech vent') AND STRFTIME('%y', procedures_icd.charttime) = '2104') AS t2 ON t1.subject_id = t2.subject_id WHERE t1.charttime < t2.charttime AND t1.hadm_id = t2.hadm_id