Measuring diaphragm shortening using ultrasonography to predict extubation success.

It is estimated that approximately 800 000 US patients annually require mechanical ventilation to treat acute respiratory failure due to medical disorders, trauma or the postoperative period. The use of mechanical ventilation is projected to increase significantly in the next few decades due to the impact of aging baby bloomers requiring more critical care resources. Although life-saving, the prolonged use of mechanical ventilation is associated with significant complications such as nosocomial pneumonia, barotrauma, patient discomfort, airway complications and respiratory muscle atrophy and accounts for a substantial percentage of the costs encountered by patients receiving care in the intensive unit. The process of weaning is a key element of mechanical ventilation and can occupy almost 50% of the total duration of mechanical ventilation. Unnecessary delays in weaning patients who are physiologically able to wean from mechanical ventilation may increase the morbidity and mortality associated with prolonged ventilation and contribute to excessive medical expenditures. Trying to decide when to wean patients from mechanical ventilation can be challenging for the clinician and has been reported by some to be more art than science. The influence of the nurse or physician’s experience in assessing the patient’s readiness to wean, the psychological profile or mental preparedness of the patient and objective indices of physiological factors crucial to enable patients to sustain spontaneous ventilation have all been reported as important factors in determining the patient’s readiness to wean. However, recent data suggests that subjective decision-making of the clinicians is often wrong when predicting successful weaning outcome. Some authors have reported that the clinical prediction of extubation success is often incorrect with the decision often skewed towards the continuation of mechanical ventilation. Objective and precise parameters that can determine the optimal timing of extubation are needed, but extremely limited. Bedside measurements used to predict weaning outcomes such as the level of spontaneous minute ventilation during unassisted breathing, ability to increase maximum voluntary ventilation, magnitude of negative inspiratory force generation and rate of breathing frequency have done little to improve the timing of successful weaning from mechanical ventilation. Use of more exquisite techniques to predict weaning outcome during Correspondence to Gerard J Criner, Pulmonary and Critical Care Medicine and Temple Lung Center, Temple University School of Medicine, 745 Parkinson Pavilion, 3401 North Broad Street, Philadelphia, PA 19140, USA; [email protected]