Model for the association between pathological features, physiological alterations and their association with pathological and clinical features. Model for the association between pathological features, physiological alterations and their association with pathological and clinical features. Filled arrows represent strong and/or demonstrated associations; dotted arrows represent associations seen in end-stage disease. V′/Q′: ventilation/perfusion ratio; PH: pulmonary hypertension. Laurent Plantier et al. Eur Respir Rev 2018;27:170062 ©2018 by European Respiratory Society