RSBI Calculator
Frequency over tidal volume — the classic rapid-shallow-breathing screen during a spontaneous breathing trial.
Written by Apex Respiratory Editorial Team
Enter rate and tidal volume to calculate the index.
Using RSBI honestly
Yang and Tobin measured f/VT during one minute of unsupported breathing: an index under 105 predicted weaning success, while rapid-shallow patterns above it predicted failure. Pressure support, PEEP, and timing of the measurement all shift the number — follow your institution’s SBT protocol for how to measure it.
RSBI is one screen, not a verdict. Mental status, secretions, cough strength, hemodynamics, oxygenation, and the reason for intubation all belong in the liberation decision.
Educational use only. This material supports respiratory therapy education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or physician orders. Always follow facility policies and current provider orders, and verify calculations independently before clinical use.
Sources
- Yang KL, Tobin MJ. A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. N Engl J Med. 1991;324(21):1445-1450.
- Ouellette DR, Patel S, Girard TD, et al. Liberation from mechanical ventilation in critically ill adults: an official ATS/ACCP clinical practice guideline. Chest. 2017;151(1):166-180.