A method for detecting a state of a dressing includes measuring air pressure within a tube. The tube provides airflow between a pump device and the dressing. The method also includes determining whether the air pressure differs from a pressure setpoint by more than a preset limit, and running the pump to cause the air pressure to approach the pressure setpoint. In response to a determination that the air pressure does not differ from the pressure setpoint by more than the preset limit, the method also includes determining a duration of time since a last running of the pump, determining whether the duration of time since the last running of the pump exceeds a threshold duration, and, in response to a determination that the duration of time since the last running of the pump exceeds the threshold duration, generating an alert that indicates that the dressing is full.