Ventilation therapy for patients with COPD

Acute ventilatory failure in COPD is caused by impaired respiratory mechanics and an imbalance of capacity and load of the respiratory muscles. Continuous positive airway pressure (CPAP), pressure support ventilation (PSV), proportional assist ventilation (PAV) or controlled mechanical ventilation (CMV) are effective in unloading the respiratory pump. CPAP reduces the inspiratory pressure time product by reducing the elastic work of breathing due to intrinsic PEEP (PEEPi). PSV and PAV reduce the work of breathing and additionally improve alveolar ventilation and CO2 elimination. In spontaneous breathing patients these modes of ventilation should be applied non invasively by using a face mask. In CMV, hyperinflation should be avoided by choice of low tidal volumes and long exspiratory times (low respiratory rate, I:E ratio 1:3, 1:4). In the weaning from CMV, PSV or PAV and CPAP is used. There seems to be a beneficial effect in nocturnal intermittent nonivasive ventilation (NPPV) in chronic hypercapnic stable COPD patients with documented hypoventilation during the night, which is reversible by NPPV.