Oxygen desaturation during a 4-minute step test: predicting survival in idiopathic pulmonary fibrosis

Sarcoidosis Vasc Diffuse Lung Dis. 2007 Mar;24(1):70-6.


Background and aim: PaO2 during exertion is a significant predictor of IPF survival. The aim of study was to assess oxygen desaturation for predicting survival in IPF patients at the end of a 4-minute step test.

Methods: A longitudinal study was done in 59 patients with IPF from February 1998 to January 2005. Upon initial examination, lung function testing was performed, as were 4-minute step tests, in which patients stepped up and down on a 20-cm single step at a self-paced rate. In the final minute, oxygen saturation by pulse oximetry (SpO2) was measured.

Results: Median survival was 58 months. SpO2 at rest and during stepping, dyspnea score, as well as FVC% and DLCO% were found to be significant predictors of mortality. Desaturation to 89% or less,correlated with a hazard ratio of 2.39 for IPF mortality (95% CI, 1.16-3.63; p < 0.0001). In patients with such desaturation, four-year survival was 39%, compared to 96% in those with no desaturation. In a multivariate Cox analysis, only SpO2 during stepping remained significant (p < 0.0001). A DLco < 45% of predicted (n=40 patients) correlated with a hazard ratio of 2.23 for mortality (95% CI, 0.73-3.71; p < 0.0001). When the analysis was repeated including DLco, SpO2 and DLco remained significant (p < 0.05).

Conclusion: Desaturation to 89% or less in a 4-min step test is a strong predictor of mortality in IPF patients.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Exercise Test*
  • Female
  • Humans
  • Kaplan-Meier Estimate
  • Longitudinal Studies
  • Male
  • Middle Aged
  • Oximetry
  • Oxygen / blood*
  • Oxygen Consumption
  • Prognosis
  • Pulmonary Fibrosis / mortality*
  • Pulmonary Fibrosis / physiopathology
  • Survival Analysis


  • Oxygen