number of novel desaturation indices have been proposed in patients with ILD, with the aim of
improving the ability of the 6MWT to predict mortality. These include the distance–saturation product
[42–45], the desaturation area [46] and the desaturation–distance ratio [47]. As only a small number of
studies are available, the utility of these measures has not been confirmed and they are not routinely
collected during the 6MWT.