This complication may be due to the loss of sympathetic tone when the work of breathing is quickly reduced, to sedative use, to alkalosis due to overventilation, or to increased positive intrathoracic pressures leading to diminished venous return and lower cardiac output. Elderly patients who are hypovolemic as a result of an underlying disease are particularly at risk of hypotension and its sequelae. The endotracheal tube reduces the normal protective mechanisms that defend the airway from aspiration and colonization with bacteria. Other complications of prolonged endotracheal intubation include pressure necrosis on the tracheal mucosa from overinflated cuffs or from movement of cuffs with movement of the tube. The cuff pressure should not exceed 25 mm Hg because blood flow to the mucosa is decreased and necrosis may occur.
Many patients feel more comfortable with a tracheostomy.
Mechanical Ventilation Initially, most patients are best treated by a mode of mechanical ventilation that completely assumes the work of breathing and minimizes the patient's efforts. Minimizing airway pressure and providing the most uniform ventilation possible is an important goal, especially when stiff lungs limit maximum volume. A ventilator in control mode delivers its set volume at a specific frequency and will not respond to the patient's efforts to take more frequent breaths. A ventilator in pressure-support mode provides specific airway pressure during inspiration only. Pressure may be set high to do most or all of the inspiratory work of breathing or low to provide partial support.