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Weaning from mechanical ventilation.

Surgical critical care began as a formal discipline in the 1960s and was driven in large part by the ability to provide external mechanical ventilator support. Accompanying the ability to support the work of breathing using invasive techniques was the need to determine when that support was no longer required, and that the work of breathing could be safely and durably managed by the patient. Originally taking the form of a bedside clinical assessment including an assessment of muscle strength, secretions, level of alertness, and the ability to follow commands, modern assessments of liberation from mechanical ventilation also includes some objective determinations of the ability to manage the work of breathing. These assessments include measured and derived indices of ventilation as well as a trial period of breathing on a reduced level of support. These brief trials are part of the process of weaning from mechanical ventilation and are termed “spontaneous breathing trials.” In this section, we explore the requirements for beginning weaning, how to assess the adequacy of weaning and the likelihood of successful liberation from mechanical ventilation, decision support tools, and an assessment of opportunities for improvement in these assessment tools for use in the intensive care unit (ICU). Liberation from mechanical ventilation in the operating room is a separate discussion and beyond the scope of this chapter.