Cardiopulmonary Exercise Testing Helps Predict Mortality in Idiopathic Pulmonary Fibrosis

Laurie Barclay, MD

February 26, 2009

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February 26, 2009 — Cardiopulmonary exercise testing (CPET) helps predict mortality in idiopathic pulmonary fibrosis (IPF), according to the results of a retrospective study reported in the March 1 issue of the American Journal of Respiratory and Critical Care Medicine.

"IPF is characterized by progressive dyspnea, impaired gas exchange, and ultimate mortality," write Charlene D. Fell, from the University of Calgary in Calgary, Canada, and colleagues. "Prognosis in...IPF is poor. Predicting prognosis by examining exercise performance with the six-minute-walk test has led to conflicting results."

The goal of this study was to determine whether maximal oxygen uptake (VO2max) during CPET at baseline and with short-term longitudinal measures would predict mortality in patients with IPF. The investigators reviewed data from 117 patients with IPF and longitudinal CPET and calculated survival from the date of the first CPET.

After adjustment for age, sex, smoking status, baseline forced vital capacity, and baseline diffusion capacity for carbon monoxide, patients with baseline VO2max of less than 8.3 mL/kg/minute had an increased risk for death (n = 8; hazard ratio [HR], 3.24; 95% confidence interval [CI], 1.10 - 9.56; P = .03). The investigators could not identify a unit change in VO2max that predicted survival in this cohort.

"A threshold maximal oxygen uptake of 8.3 ml/kg/min during cardiopulmonary exercise testing at baseline adds prognostic information for patients with IPF," the study authors write.

Limitations of this study include patients not evaluated for the presence of pulmonary hypertension, varied nature of protocols used in the patient sample, possible selection bias, and lack of data on acute exacerbations of IPF or other acute events.

"A baseline VO2max less than 8.3 ml/kg/min threshold was identified, below which the risk of death was greatly increased," the study authors conclude. "This study provides an easy-to-use threshold for VO2max for patients with IPF that predicts an increased risk of death. An unexpected finding was that not all patients with VO2max below threshold desaturated during a 6MWT [6-minute-walk test]."

The National Institute of Health National Heart, Lung, and Blood Institute supported this study. Dr. Fell was supported by the Alberta Heritage Foundation for Medical Research. Four of the study authors have disclosed various financial relationships with Actelion, Altana Pharma, Boehringer Ingelheim, Pfizer, GlaxoSmithKline, Novartis, Sepracor, Schering-Plough, Astra, Genzyme, and/or Intermune. The remaining study authors have disclosed no relevant financial relationships.

Am J Respir Crit Care Med. 2009;179:402-407.

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