Fig. 2

a-c Sleep study, two channel recordings. a) Initial study in a 45 year-old woman with thoracic restriction showing satisfactory oxygenation and mild nocturnal hypercapnia. b) Repeat evaluation after 6 months showing respiratory failure. c) After elective initiation of Bi-level Positive Airway Pressure Ventilation, showing stabilization of nighttime gas exchange which was associated in an improved clinical state