title: Risk stratification by the lower limit of normal of FEV1/FVC for postoperative outcomes in patients with COPD undergoing thoracic surgery.
abstract: BACKGROUND
  Mounting evidence suggests that airway obstruction defined by the lower limit of normal (LLN) of forced expiration volume in 1s (FEV1)/forced vital capacity (FVC) might be an important predictor of mortality in patients with an FEV1/FVC ratio below 0.70. Although better risk stratification for postoperative outcomes in patients with chronic obstructive pulmonary disease (COPD) undergoing thoracic surgery is warranted, whether an FEV1/FVC ratio below 0.70 but above the LLN (i.e., in-between) could identify patients at risk for adverse postoperative outcomes has not been fully evaluated.
  
  
  METHODS
  To determine the clinical impact of this "in-between" group of patients with COPD, we evaluated whether classification of the in-between group and the COPD group with FEV1/FVC ratios below 0.70 and below the LLN could provide more accurate risk stratification for postoperative outcomes in COPD patients undergoing thoracic surgery.
  
  
  RESULTS
  The criterion of LLN classified 302 patients with an FEV1/FVC ratio below 0.70 into either the in-between group (124 cases) or the COPD group (178 cases). The COPD group showed a 3-fold increase in prolonged oxygen therapy (POT) and a 50% increase in prolonged postoperative stay (PPS), as compared with the in-between group, with an adjusted odds ratio of 3.068 (95% confidence interval: 1.806-5.213) for POT.
  
  
  CONCLUSIONS
  Based on the finding that the in-between group could independently identify patients at risk for adverse postoperative outcomes, LLN assessment of the FEV1/FVC ratio might provide more accurate risk stratification in COPD patients undergoing thoracic surgery.
authors.affiliation: Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan. Electronic address: sosuka@med.nagoya-u.ac.jp.
authors.forename: Satoko
authors.initials: S
authors.lastname: Osuka
authors.affiliation: Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan. Electronic address: hashinao@med.nagoya-u.ac.jp.
authors.forename: Naozumi
authors.initials: N
authors.lastname: Hashimoto
authors.affiliation: Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan. Electronic address: sakakoji@med.nagoya-u.ac.jp.
authors.forename: Koji
authors.initials: K
authors.lastname: Sakamoto
authors.affiliation: Department of Preventive Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan. Electronic address: wakai@med.nagoya-u.ac.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakai
authors.affiliation: Department of Thoracic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan. Electronic address: k-yokoi@med.nagoya-u.ac.jp.
authors.forename: Kohei
authors.initials: K
authors.lastname: Yokoi
authors.affiliation: Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan. Electronic address: yhasega@med.nagoya-u.ac.jp.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Hasegawa
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D006931:Hyperbaric Oxygenation / Q000706:statistics & numerical data; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000517:prevention & control; D011184:Postoperative Period; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000601:surgery; D012306:Risk; D018570:Risk Assessment / Q000379:methods*; D019616:Thoracic Surgical Procedures; D016896:Treatment Outcome; D014797:Vital Capacity
keywords: 0.70 fixed ratio; Chronic obstructive lung disease; Lower limit of normal; Risk stratification; Thoracic surgery