title: The inspiratory capacity/total lung capacity ratio as a predictor of survival in an emphysematous phenotype of chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Forced expiratory volume in 1 second (FEV1) grades severity of COPD and predicts survival. We hypothesize that the inspiratory capacity/total lung capacity (IC/TLC) ratio, a sensitive measure of static lung hyperinflation, may have a significant association with survival in an emphysematous phenotype of COPD.
  
  
  OBJECTIVE
  To access the association between IC/TLC and survival in an emphysematous phenotype of COPD.
  
  
  METHODS
  We performed a retrospective analysis of a large pulmonary function (PF) database with 39,050 entries, from April 1978 to October 2009. Emphysematous COPD was defined as reduced FEV1/forced vital capacity (FVC), increased TLC, and reduced diffusing capacity of the lungs for carbon monoxide (DLCO; beyond 95% confidence intervals [CIs]). We evaluated the association between survival in emphysematous COPD patients and the IC/TLC ratio evaluated both as dichotomous (≤25% vs >25%) and continuous predictors. Five hundred and ninety-six patients had reported death dates.
  
  
  RESULTS
  Univariate analysis revealed that IC/TLC ≤25% was a significant predictor of death (hazard ratio [HR]: 2.39, P<0.0001). Median survivals were respectively 4.3 (95% CI: 3.8-4.9) and 11.9 years (95% CI: 10.3-13.2). Multivariable analysis revealed age (HR: 1.19, 95% CI: 1.14-1.24), female sex (HR: 0.69, 95% CI: 0.60-0.83), and IC/TLC ≤25% (HR: 1.69, 95% CI: 1.34-2.13) were related to the risk of death. Univariate analysis showed that continuous IC/TLC was associated with death, with an HR of 1.66 (95% CI: 1.52-1.81) for a 10% decrease in IC/TLC.
  
  
  CONCLUSIONS
  Adjusting for age and sex, IC/TLC ≤25% is related to increased risk of death, and IC/TLC as a continuum, is a significant predictor of mortality in emphysematous COPD patients.
authors.affiliation: Cedars-Sinai Medical Center, Division of Pulmonary and Critical Care Medicine, Los Angeles, CA, USA.
authors.forename: Aimee
authors.initials: A
authors.lastname: French
authors.affiliation: Cedars-Sinai Medical Center, Division of Pulmonary and Critical Care Medicine, Los Angeles, CA, USA.
authors.forename: David
authors.initials: D
authors.lastname: Balfe
authors.affiliation: Cedars-Sinai Medical Center, Division of Pulmonary and Critical Care Medicine, Los Angeles, CA, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Mirocha
authors.affiliation: Cedars-Sinai Medical Center, Division of Pulmonary and Critical Care Medicine, Los Angeles, CA, USA.
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Falk
authors.affiliation: Cedars-Sinai Medical Center, Division of Pulmonary and Critical Care Medicine, Los Angeles, CA, USA.
authors.forename: Zab
authors.initials: Z
authors.lastname: Mosenifar
mesh_terms: D000367:Age Factors; D000368:Aged; D016009:Chi-Square Distribution; D016208:Databases, Factual; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007320:Inspiratory Capacity; D053208:Kaplan-Meier Estimate; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010641:Phenotype; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D011653:Pulmonary Diffusing Capacity; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology*; D011656:Pulmonary Emphysema / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology*; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D012737:Sex Factors; D014109:Total Lung Capacity; D014797:Vital Capacity
keywords: emphysema; mortality; pulmonary function testing