Relationship between outcome measures of six-minute walk test and baselinelung function in patients with interstitial lung disease

Background and aim of the work: In patients with interstitial lung disease (LLD), the six-minute walk test (6MWT) has been rarely used, and up till no w, the relationship between outcome measures of the test and baseline lung function has not yet been examined. Therefore, we assessed walk distance, o xygen desaturation, and breathlessness perception during 6MWT, and their re lationships to baseline lung function in patients with ILD. Methods: Forty ILD patients with history of breathlessness during physical exertion perfor med a 6MWT following a standard protocol. Breathlessness perception during walk was assessed by visual analogue scale (VAS, in mm). Results: The mean walk distance was 487 meters (range 271-689). Mean baseline oxygen saturati on (Base SpO(2), %) was 94 % and was reduced during walk, either as mean ox ygen saturation (Mean SpO(2), 89 %, p < 0.001) or as mean fall in oxygen sa turation during walk (Fall SpO(2), 5%). Furthermore, VAS significantly incr eased after walk (5 mm to 44 mm, p < 0.001). A close relationship of TLco a nd TLC to walk distance and Fall SpO(2) was found (r = 0.45 and 0.42 and r = -0.75 and -0.64, respectively; p < 0.001, each). On the basis of regressi on equations by stepwise multiple regression analysis, walk distance was pr edicted by age and FVC (r(2) = 0.50), Mean SpO(2) by TLco and Base SpO(2) ( r(2) = 0.80), and Fail SpO(2) only by TLco (r(2) = 0.57). Breathlessness pe rception was not reliably predicted by any assessed variables. Conclusions: We confirmed that 6MWT provides a global evaluation of sub-maximal exercis e capacity in ILD patients. We also found that walk distance and oxygen des aturation, but not breathlessness perception during walk, are strictly rela ted to baseline lung function.