title: The importance of controlling PaCO₂ throughout long-term noninvasive ventilation.
abstract: BACKGROUND
  The significance of changes in P(aCO2) during long-term noninvasive ventilation (NIV) on prognosis remains unclear. We aimed to clarify whether stabilizing P(aCO2) during NIV had a favorable prognostic effect.
  
  
  METHODS
  Data from 190 subjects with restrictive thoracic disease and who received long-term NIV were studied retrospectively. The annual change in P(aCO2) during NIV was determined using a simple linear regression method for each subject who had at least 4 6-month intervals of P(aCO2) data. Annual changes in P(aCO2) during long-term NIV and possible confounders were analyzed with discontinuation of long-term NIV as the main outcome.
  
  
  RESULTS
  One hundred and twenty-five subjects who had > 4 6-month intervals of P(aCO2) data were included in the study. P(aCO2) during long-term NIV decreased in 41 subjects (group 1; < 0 mm Hg/y), increased slightly in 42 subjects (group 2; between 0 and 1.85 mm Hg/y), and increased significantly in 42 subjects (group 3; > 1.85 mm Hg/y). Smaller annual changes in P(aCO2) (P < .001) and a control ventilator mode (P = .008) were associated with a significantly higher probability of continuing NIV, compared with decreased P(aCO2) 3-6 months after the start of long-term NIV (P = .11). The 10-y probability of continuing NIV was 69% in group 1, 39% in group 2, and 12% in group 3.
  
  
  CONCLUSIONS
  A decrease in the annual change of P(aCO2) during long-term NIV was shown to be a significantly prognostically favorable factor. Efforts to reduce P(aCO2) should be made if P(aCO2) increases at a greater rate during long-term NIV.
authors.affiliation: Department of Respiratory Medicine, National Hospital Organization Minami-Kyoto Hospital, Kyoto tomomasa@kuhp.kyoto-u.ac.jp.
authors.forename: Tomomasa
authors.initials: T
authors.lastname: Tsuboi
authors.affiliation: Department of Respiratory Care and Sleep Control Medicine, Kyoto University Graduate School of Medicine, Kyoto.
authors.forename: Toru
authors.initials: T
authors.lastname: Oga
authors.affiliation: Department of Respiratory Medicine, National Hospital Organization Minami-Kyoto Hospital, Kyoto.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Sumi
authors.affiliation: Department of Respiratory Medicine, National Tokyo Hospital, Tokyo.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Machida
authors.affiliation: Sleep Medical Centre, Osaka Kaisei Hospital, Osaka, Japan.
authors.forename: Motoharu
authors.initials: M
authors.lastname: Ohi
authors.affiliation: Department of Respiratory Care and Sleep Control Medicine, Kyoto University Graduate School of Medicine, Kyoto.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Chin
mesh_terms: D000368:Aged; D001784:Blood Gas Analysis; D002908:Chronic Disease; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006935:Hypercapnia / Q000097:blood* / Q000175:diagnosis / Q000209:etiology; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods*; D063087:Noninvasive Ventilation / Q000379:methods*; D012131:Respiratory Insufficiency / Q000097:blood / Q000150:complications / Q000628:therapy*; D012189:Retrospective Studies; D013997:Time Factors
keywords: PCO2; chronic respiratory failure; home mechanical ventilation; hypercapnia; noninvasive ventilation; restrictive thoracic disease