Non-invasive ventilation in chronic obstructive pulmonary disease

Advanced chronic obstructive pulmonary disease (COPD) is associated with peripheral and respiratory muscular weakness with nocturnal and daytime arterial blood gas abnormalities (including hypercapnia) leading to chronic respiratory failure (CRF). At present, long-term oxygen therapy (LTOT) is the only recognized long-term treatment that has been shown to significantly improve survival in these patients. An alternative therapeutic approach proposed, especially in patients with worsening hypercapnia, is nocturnal non-invasive ventilation (NIV). The three main theories that explain the efficacy of NIV, as applied by positive pressure (NIPPV), in these patients are: opportunity for resting of fatigued respiratory muscles, improvement in thoracic-pulmonary mechanics, and the ‘resetting’ of the central respiratory drive. In contrast with the strong evidence favouring the use of NIV in acute exacerbation of COPD, many studies performed in severe but stable patients have shown inconsistent and conflicting results. In the short term, NIV has been shown to reduce the rate of hospitalization, as well as to improve both the patient’s quality of life and their functional status. However, long-term assessments did not find any effect on survival and the strongest outcomes were not affected by the use of NIPPV even when added to LTOT. Recommendations of an international consensus conference published in 1999 provided the basis for NIV prescription in stable advanced COPD patients – nocturnal hypoventilation, sleep fragmentation and daytime arterial hypercapnia – which are still considered the optimal indications for domiciliary NIV, in particular in the presence of severe-progressive deterioration of the clinical condition and instability of respiratory function.