The Rapid Shallow Breathing Index (RSBI) is a bedside tool used to predict the likelihood of successful weaning from mechanical ventilation. First described by Yang and Tobin in 1991, the index is based on the observation that patients who breathe rapidly and shallowly during a spontaneous breathing trial are less likely to tolerate extubation. The RSBI is calculated by dividing the respiratory rate (breaths per minute) by the tidal volume (liters). A higher RSBI indicates rapid shallow breathing and correlates with a higher risk of weaning failure, whereas lower values suggest stronger respiratory performance and a better chance of successful liberation from the ventilator.

This tool is widely used in intensive care units as part of structured weaning protocols. It is most commonly assessed after the patient has achieved stability, adequate oxygenation, and resolution or improvement of the underlying condition that led to intubation. While RSBI is practical, it should never be used as the sole determinant of extubation readiness. Other clinical considerations include mental status, cough strength, airway protection, secretion load, hemodynamic stability, and overall disease course.