Chest physiotherapy involves techniques like percussion, vibration, and postural drainage to mobilize pulmonary secretions in patients who have difficulty coughing. The goals are to move secretions to central airways using gravity and then eliminate them by coughing or suctioning. Common techniques include postural drainage, percussion, vibration, and the active cycle of breathing technique. Chest physiotherapy is often used to treat conditions that cause excess secretions like cystic fibrosis.