Effective expectoration or sputum aspiration can ensure sufficient draining of secretion from trachea, but it has no direct effects on drainage from bronchi and alveoli. Each step of cough reflex should be considered in order to deliver effective expectoration. Peak cough expiratory flow is the main indicator for cough efficiency. In patients who have artificial airways, inner diameter of tracheal catheter, management of cuff and high flow ventilation need to be carefully considered. The main methods to improve draining of bronchus are to decrease airway resistance and to improve airway ciliary movement. The key to maintain efficient pulmonary alveoli drainage is to prevent alveolar atelectasis, of which respiration and ventilation with large tidal volume are major maneuvers. As for implication of modern ventilators, we should pay more attention closely to deficiency of inspired tidal volume due to unsuitable setup of ventilation parameters. Other methods of keeping alveolar drainage include controlling FiO2 and keeping suitable spontaneously breathing.