A flutter valve is a special type of one way valve use in respiratory medicine. It is usually placed on the end of a chest tube to prevent air from travelling back along the tube and into the patient's chest. It is most commonly used to help remove air from a pneumothorax (i.e. air between the patient's lungs and chest wall). The valve is usually designed as a rubber sleeve within a plastic case where the rubber sleeve is arranged so that when air passes through the valve one way the sleeve opens and lets the air through. However when air is sucked back the other way the sleeve closes off and no air is allowed backwards. This construction enables it to act as a one-way valve allowing air (or fluid) to flow only one way along the drainage tube. The end of the drainage tube is placed inside the patient's chest cavity, within the air or fluid to be drained. The flutter valve is placed in the appropriate orientation (most packages are designed so the valve can only be connected in the appropriate orientation) and the pneumothorax is thus evacuated from the patient's chest.