Disclosed are methods and devices for regulating fluid flow in one or more lung regions that are supplied fluid through one or more collateral pathways. An identified region of the lung is targeted for volume reduction or collapse. The targeted lung region is then bronchially isolated to inhibit air from flowing into the targeted lung region through bronchial pathways that directly feed air to the targeted lung region. If the targeted lung region does not collapse after bronchially isolating the targeted lung region, then it is possible that a collateral pathway is feeding air to the targeted lung region, thereby preventing the targeted lung region from collapsing. In such a case, the collateral pathway is identified and air flow into the targeted lung region via the collateral pathway is reduced or eliminated.