This will be a prospective, open-label, crossover study in up to 12 stable subjects with chronic respiratory insufficiency who require LTOT. Each subject's standard oxygen therapy will be used as the control treatment and compared to the test ventilator system during selected activities of daily living. Subjects will participate in the study for up to 9 home visits, with Visits 1 and 2 each lasting for approximately 4 hours, and Visits 3-9 lasting approximately 1-2 hours each. Subjects may discontinue study participation at any time.