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. Pressure-support mode may be helpful during weaning efforts and when patients need only a minimal level of support and have an adequate respiratory drive. However, PEEP increases the risk of barotrauma, diminishes venous return, may increase intracranial pressure, and may increase fluid retention through changes in antidiuretic hormone and atrial natriuretic factor. Opioids decrease breathlessness but may cause hypotension and ileus.
Benzodiazepines are effective and are commonly used.
Patients must always receive adequate sedation when receiving neuromuscular blockade, which may be needed when patients have difficulty matching their respiratory pattern to the ventilator. Neuromuscular blockade may reduce airway pressures and risk of barotrauma. Elderly patients with nutritional problems may have less muscle mass, especially the fast twitch fibers that may be related to inspiratory work. Nutritional deficiency may worsen host defenses. However, because carbohydrates produce more CO 2 per calorie than fat, feedings with large proportions of carbohydrates require greater ventilation.