A chest drainage system includes a collection device and a fluid pathway configured to extend from the collection device to a patient. A pressure source is configured to selectively provide sub-atmospheric pressure to the fluid pathway. The system is configured to introduce sub-atmospheric pressure from the pressure source at a substantially constant target pressure and at a dynamic pressure that varies from the target pressure. A method is also disclosed for draining a pleural cavity of a patient. The method involves applying dynamic pressure to the pleural cavity of a patient by changing sub-atmospheric pressure applied to the patient such that the patient's pleura moves without any or limited patient activity, thus facilitating removal of loculated fluid from the pleural cavity. The method may involve the use of the chest drain system.