Eighteen COPD patients with respiratory insufficiency received the treatment of pursed lips breathing. The results showed that respiratory rate reduced (from 21.4 +/- 12.6 to 14.8 +/- 4.1 breath/min) and tidal volume increased (from 356.9 +/- 96.7 to 462.0 +/- 147.1 ml) significantly. In the meantime, arterial partial pressure of carbon dioxide decreased and arterial partial pressure of oxygen increased significantly (all p values less than 0.01).