Fig. 1. Histogram showing the daily time in hours (bars) spent without mechanical ventilation on continuous positive airway pressure. Day 0 designates the first session of hypnosis; arrows = the hypnotic sessions; squares = daily mean arterial oxygen partial pressure/fraction of inspired oxygen ratio (right ordinate axis; mmHg); triangles = indicated daily mean arterial carbon dioxide partial pressure per minute ventilation ratio (right ordinate axis; mmHg · l−1· min−1· 10).