The main indication of LTO is COPD with chronic respiratory failure, where it improves life expectancy. By extension, LTO may be proposed to other etiologies of CRF with chronic documented hypoxemia. Daily duration is at least 15H per day. Non invasive ventilation (NIV) represents facial or nasal ventilation. Consensus indications of NIV are restrictive pulmonary diseases (chest wall and /or parenchmal sequelae, neuromuscular diseases, or obesity hypoventilation syndrome) Real role of NIV in log-term management of COPD remains controversial.