Use of the 15-steps climbing exercise oximetry test in patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is often associated with exercise-induced hypoxemia. Although maximal oxygen consumption (VO_2(max)) is considered the gold-standard index of functional capacity in IPF, its measurement requires sophisticated equipment and trained personnel. The aim of the present study was to investigate the value of the simple 15-steps climbing exercise oximetry test in patients with IPF. The 15-steps climbing test was administered to 51 patients with IPF. Pulmonary function tests (PFTs), cardiopulmonary exercise test (CPET), and the 6-min walk distance (6MWD) test were performed in the same session. Oxygen saturation in the 15-steps climbing test was measured by continuous oximetry, and quantified oxygen desaturation was determined by calculating the area under the curve of oxygen saturation from the beginning of exercise through the lowest desaturation point until recovery to baseline ("desaturation area"). There was a statistically significant correlation between all parameters of the 15-steps climbing test and both VO_2(max) on the CPET (lowest saturation, p=0.002, r=0.43; saturation difference, p=0.02, r=-0.33; recovery time, p=0.02, r=-0.32; and desaturation area, p=0.005, r=-0.39), and carbon dioxide diffusion in the lungs (DLCO) on the PFTs (lowest saturation, p=0.0001, r=0.52; saturation difference, p=0.0002, r=-0.50; recovery time, p=0.0001, r=-0.53; and desaturation area, p=0.0001, r=-0.53). On stepwise linear regression analysis, independent significant predictors of VO_2(max) were lowest saturation on the 15-steps test and the 6MWD. We concluded that the 15-steps oximetry test is a simple and accurate bedside tool for the evaluation of functional capacity in patients with IPF.