Chronic hypercapnic respiratory failure is essentially a ventilatory failure. Noninvasive ventilation (NIV ) reduces the work of breathing, improves pulmonary compliance and alveolar ventilation, corrects gas exchange disorders and improves dyspnoea. However, treatment efficacy depends on the underlying pathology, on correct timing and on patient compliance. In this context, the principal role of the primary care physician is to search for, at every visit of at risk patients, signs and symptoms of ventilatory failure and to refer the patient to a respiratory care specialist. He also plays a role in the follow up of patients under noninvasive ventilation for the detection of clinical parameters suggesting NIV failure.