Methods, systems and devices are described for temporarily or permanently evacuating stagnating air from a diseased lung area, typically for the purpose of treating COPD. Evacuation is accomplished by displacing the stagnant CO2-rich air with a readily diffusible gas using a trans-luminal indwelling catheter specially configured to remain anchored in the targeted area for long term treatment without supervision. Elevated positive gas pressure in the targeted area is then regulated via the catheter and a control unit to force under positive pressure effusion of the diffusible gas out of the area into neighboring areas while inhibiting infusion of other gases thus effecting a gradual gas volume decrease and deflation of the targeted area, thereby reducing volume of ineffective areas, increasing tidal volume of better areas, and improving lung mechanics.
