For people whose injuries are high enough to interfere with breathing, there is great emphasis on airway clearance during this stage of recovery. Weakness of respiratory muscles impairs the ability to cough effectively, allowing secretions to accumulate within the lungs. As SCI patients suffer from reduced total lung capacity and tidal volume, physical therapists teach them accessory breathing techniques (e.g. apical breathing, glossopharyngeal breathing) that typically are not taught to healthy individuals. Physical therapy treatment for airway clearance may include manual percussions and vibrations, postural drainage, respiratory muscle training, and assisted cough techniques. Patients are taught to increase their intra-abdominal pressure by leaning forward to induce cough and clear mild secretions. The quad cough technique is done lying on the back with the therapist applying pressure on the abdomen in the rhythm of the cough to maximize expiratory flow and mobilize secretions. Manual abdominal compression is another technique used to increase expiratory flow which later improves coughing. Other techniques used to manage respiratory dysfunction include respiratory muscle pacing, use of a constricting abdominal binder, ventilator-assisted speech, and mechanical ventilation.