The inspiratory capacity/total lung capacity ratio as a predictor of survival in an emphysematous phenotype of chronic obstructive pulmonary disease.

eScholarship, University of California 2015-01-01

BackgroundForced 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.ObjectivesTo access the association between IC/TLC and survival in an emphysematous phenotype of COPD.MethodsWe 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.ResultsUnivariate 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.ConclusionAdjusting 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.

Lung; Humans; Pulmonary Disease; Chronic Obstructive; Pulmonary Emphysema; Total Lung Capacity; Vital Capacity; Inspiratory Capacity; Pulmonary Diffusing Capacity; Forced Expiratory Volume; Severity of Illness Index; Multivariate Analysis; Proportional Hazards Models; Risk Factors; Chi-Square Distribution; Retrospective Studies; Predictive Value of Tests; Age Factors; Sex Factors; Phenotype; Databases; Factual; Aged; Middle Aged; Female; Male; Kaplan-Meier Estimate; emphysema; mortality; pulmonary function testing; Chronic Obstructive Pulmonary Disease; Respiratory; Respiratory System; Cardiorespiratory Medicine and Haematology; publication

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