Changes in pulmonary function test results after 1 year of therapy as predictors of survival in patients with idiopathic pulmonary fibrosis

Chest. 1995 Aug;108(2):305-10. doi: 10.1378/chest.108.2.305.

Abstract

The study group consisted of 58 patients with idiopathic pulmonary fibrosis (IPF) recognized between 1970 and 1991 who were treated for their pulmonary disease, survived for at least 1 year from the time of initiation of treatment, and had forced vital capacity (FVC) measurements at the time of diagnosis and 9 to 15 months later. Forty-four of the patients also had a single-breath diffusing capacity (Dsb) measured initially and after 9 to 15 months of treatment and 33 patients had an arterial blood gas, breathing room air at the time of diagnosis and 9 to 15 months into therapy. Patients' conditions were classified as improved, unchanged, or worse after the year of treatment based on each of the three pulmonary function tests. A > or = 10% increase in FVC, > or = 20% increase in Dsb, and > or = 5 mm Hg decrease in alveolar-arterial difference in oxygen partial pressure [P(A-a)O2] defined improved function. A > or = 10% decrease in FVC, > or = 20% decrease in Dsb, and > or = 5 mm Hg increase in P(A-a)O2 defined worse function. Patients with < 10% change in FVC, < 20% change in Dsb, and < 5 mm Hg change in P(A-a)O2 were regarded as having unchanged conditions. Kaplan-Meier survival plots and the Cox proportional hazard regression model were used to analyze survival time in relation to change in pulmonary function after 1 year of therapy. Patients with an improved or unchanged FVC at 1 year had no difference in survival (p = 0.75), but both showed enhanced survival compared with patients with a > or = 10% reduction in FVC with 1 year of treatment (p < 0.001). Patients with an improved or unchanged Dsb at 1 year also had no difference in survival (p = 0.21) but again, both showed enhanced survival compared with patients with > or = 20% decrease in Dsb with 1 year of treatment (p < 0.001). Changes in gas exchange after 1 year of treatment did not correlate with survival in the three groups. There was a trend for longer survival in improved patients compared with those with worsening gas exchange, but the p value was not significant at 0.17. We conclude that changes in the FVC and Dsb after 1 year of treatment are strongly predictive of duration of survival in patients with IPF.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Confidence Intervals
  • Female
  • Follow-Up Studies
  • Humans
  • Lung / physiopathology*
  • Male
  • Middle Aged
  • Prognosis
  • Proportional Hazards Models
  • Pulmonary Fibrosis / mortality*
  • Pulmonary Fibrosis / physiopathology*
  • Respiratory Function Tests / statistics & numerical data
  • Survival Analysis
  • Time Factors
  • Washington / epidemiology