PURPOSE: The six-minute walk-test (6mWT) is potentially useful to define prognosis in patients with idiopathic pulmonary fibrosis (IPF). The objective of this study was to determine if resting pulmonary function tests (PFT) can predict the presence of decrease of oxygen saturation (SaO2) during a 6mWT and if the walked distance correlates with the resting PFT.
METHODS: Fifty-three patients with IPF were included according to the ATS/ERS consensus definition. Pulmonary function tests (including spirometry, lung volumes and diffusing lung capacity of carbon monoxide - DLCO) and a 6mWT were performed in all patients.
RESULTS: The walked distance during a 6mWT did not correlate with age (r = -0.154; p = 0.272) or DLCO as percentage of predicted value (r = 0.261, p = 0.065), but it correlated with baseline SaO2 (r = 0.359; p = 0.007). No significant difference was found in patients who showed fall of oxygen saturation in comparison with those who did not in the proportion of the following variables: dyspnea at the moment of diagnosis (78 vs. 66%; p = 0.124), high resolution computed tomography (HRCT) showing definitive usual interstitial pneumonia (72% vs. 80%; p = 0.52) and normal functional vital capacity (FVC) as percentage of predicted value (59% vs. 77 %; p = 0.29). In contrast, there was a significant difference in FVC (61.80 ± 17.50 vs. 82.50 ± 19.02, p = 0.003) and in basal SaO2 (94.03 ± 1.98 vs. 95.87 ± 2.17, p = 0.004) between these two groups.
CONCLUSION: The fall of SaO2 during the 6mWT cannot be predicted by clinical variables or HRCT findings but it does relate to the fall of FVC. This study shows the importance of performing the 6mWT independently of the presence of dyspnea or spirometry results.
CLINICAL IMPLICATIONS: SaO2 and DLCO do not have a parallel behavior in patients with IPF and cannot mutually replace each other. Because of their prognostic implications both tests should be routinely performed.
DISCLOSURE: Luciana Molinari, No Financial Disclosure Information; No Product/Research Disclosure Information