Rapid shallow breathing index
The rapid shallow breathing index (RSBI) is a tool that is used in the weaning of mechanical ventilation on intensive care units. The RSBI is defined as the ratio of respiratory frequency to tidal volume (f/VT). People on a ventilator who cannot tolerate independent breathing tend to breathe rapidly (high frequency) and shallowly (low tidal volume), and will therefore have a high RSBI.[1]
Equation
Measurement
Measurement is done with a handheld spirometer attached to the endotracheal tube while a patient breathes room air for one minute without any ventilator assistance.[2]
Example
As an example, a patient who has a respiratory rate of 25 breaths/min and an average tidal volume of 250 mL/breath has an RSBI of (25 breaths/min)/(0.25 L) = 100 breaths/min/L
History
The concept was introduced in a 1991 paper by physicians from the University of Texas Health Science Center at Houston and Stritch School of Medicine at Loyola University in Chicago.[1]
Weaning Readiness
An RSBI score of less than 65[3] indicating a relatively low respiratory rate compared to tidal volume is generally considered as an indication of weaning readiness.
