Respiratory failure and mechanical ventilation: Pathophysiology and methods of promoting weaning

Respiratory failure may be manifested either by impaired gas exchange or by impaired ventilatory function. The latter results in more severe problems in weaning patients from mechanical ventilation. Ventilatory failure may result from inadequate respiratory drive, excessive respiratory workload, inadequate respiratory muscle endurance, or a combination of these factors. Simple bedside tests of ventilatory function are useful for evaluating the severity of respiratory failure and the potential for successful weaning. However, even when the results are discouraging, properly monitored weaning attempts may be successful. Although there are no convincing data to prove the superiority of either the T-piece weaning method or intermittent mandatory ventilation, we prefer to use the T-piece, and describe here a comprehensive approach to weaning the difficult patient. New approaches that have been developed to help wean difficult patients include continuous positive airway pressure breathing (CPAP), pharmacologic interventions (aminophylline and others), nutritional supplementation, inspiratory muscle resistive training, psychiatric interventions, and chronic mechanical ventilation.