Effect of nocturnal oxygen and acetazolamide on exercise performance in patients with pre-capillary pulmonary hypertension and sleep-disturbed breathing: randomized, double-blind, cross-over trial. - Ulrich S; Keusch S; Hildenbrand FF; Lo Cascio C; Huber LC; Tanner FC; Speich R; Bloch KE (European heart journal, 2015)