Discontinuing mechanical ventilation is a two step process:
- Readiness testing — Readiness testing refers to the evaluation of objective clinical criteria in order to decide whether a patient is ready to begin the process of discontinuing mechanical ventilation. Some clinicians also use physiological tests, known as weaning predictors, to predict whether a patient is ready because they are hesitant to begin weaning on the basis of clinical criteria alone. The rapid shallow breathing index (RSBI) is one of the best studied and most commonly used weaning predictors.
- Weaning — Weaning is the process of decreasing ventilator support and allowing patients to assume a greater proportion of their ventilation. It may involve either an immediate shift from full ventilatory support to a period of breathing without assistance from the ventilator (ie, a spontaneous breathing trial [SBT]) or a gradual reduction in the amount of ventilator support [1,2]. Regardless of which approach is chosen, extubation is considered once the patient demonstrates the ability to breathe without the ventilator.
The definition, accuracy, effect on clinical outcomes, and measurement of the RSBI are reviewed here. The role of the RSBI in readiness testing is described separately. (See "Weaning from mechanical ventilation: Readiness testing", section on 'Approach to readiness testing'.)
General aspects of readiness testing, methods of weaning, and extubation are discussed elsewhere. (See "Weaning from mechanical ventilation: Readiness testing" and "Methods of weaning from mechanical ventilation" and "Extubation management".)
The rapid shallow breathing index (RSBI) is the ratio of respiratory frequency to tidal volume (f/VT). As an example, a patient who has a respiratory rate of 25 breaths/min and a tidal volume of 250 mL/breath has an RSBI of (25 breaths/min)/(.25 L) = 100 breaths/min/L.