π« RSBI Calculator
The Yang-Tobin index for ventilator weaning.
For informational purposes only, not medical advice. Consult a healthcare professional.
The rapid shallow breathing index, also called the Yang-Tobin index, is the most studied predictor of ventilator weaning success: respiratory rate divided by tidal volume in liters. Patients who breathe fast and shallow, high rate over tiny volumes, score high and usually fail weaning; those with comfortable deep breaths score low and usually succeed. The original 1991 study found 105 breaths per minute per liter separated success from failure with striking accuracy. This calculator computes it for ICU teaching and reference.
How to Use This Calculator
Enter the spontaneous respiratory rate and tidal volume in milliliters during a weaning trial. The calculator divides rate by volume in liters.
Measure during a spontaneous breathing trial, not on full ventilator support. The index tests the patient effort, not the machine.
Enter respiratory rate per minute and average tidal volume in mL. The calculator converts to liters internally.
Read the index. Under 105 predicts weaning success; above it predicts failure in the original study.
How the Math Works
Divide respiratory rate by tidal volume in liters. A rate of 22 with 450 mL tidal volume gives 22 divided by 0.45, about 49. The threshold of 105 came from Yang and Tobin measurements during T-piece trials: below 105 predicted successful weaning, above predicted failure, with sensitivity and specificity in the 90s in the original cohort. Later studies show more modest performance, but it remains the best single-number weaning predictor. It is measured during minimal support so the patient own effort shows; on full assist-control the ventilator does the work and the number is meaningless.
Worked Example
During a spontaneous breathing trial the patient breathes 22 times a minute with 450 mL tidal volumes, giving an RSBI of 49. That sits well under the 105 threshold the calculator shows, predicting weaning success. Had the rate been 35 with 250 mL volumes, the index would read 140 and the trial would more likely end in fatigue and failure.
Reading Your Result
Under 105 favors a weaning and extubation attempt when the other readiness criteria are met: adequate cough, manageable secretions, hemodynamic stability, and acceptable gas exchange. Between 105 and 130 is a gray zone where some patients still succeed, especially with a strong cough and good mentation. Above 130, failure is likely and continued support with daily reassessment is the norm. RSBI is one input to the weaning decision, alongside the clinical picture, never a standalone extubation order.
| RSBI | Prediction | Action |
|---|---|---|
| Under 105 | Weaning likely | Consider extubation if other criteria met |
| 105-130 | Uncertain | Weigh cough, mentation, gases |
| Above 130 | Weaning unlikely | Continue support, reassess daily |
Limitations
RSBI was validated in specific trial conditions and performs less dramatically in unselected ICU populations. It does not assess cough strength, secretion burden, or airway protection, which decide extubation independently of weaning. Fever, pain, and anxiety raise the rate and inflate the index transiently. Measure during a proper spontaneous trial; numbers from fully supported ventilation mislead.
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For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is RSBI?
The rapid shallow breathing index: respiratory rate divided by tidal volume in liters, measured during a spontaneous breathing trial. Also called the Yang-Tobin index after its 1991 describers. Under 105 predicts successful ventilator weaning; above predicts failure.
How is RSBI measured?
During minimal ventilator support such as a T-piece or low pressure-support trial, after the patient settles: count the respiratory rate and average the tidal volume over a minute, then divide. Agitation or fever during measurement inflates the rate and the index.
What RSBI predicts extubation success?
Under 105 is the classic threshold from Yang and Tobin. It predicts weaning from the ventilator; extubation additionally needs airway protection, cough, and secretion management. A good RSBI with a weak cough still fails extubation.
Why do COPD patients have higher RSBI?
Their baseline breathing pattern runs faster and shallower from hyperinflation and weak diaphragms, so their RSBI sits higher even when they wean successfully. Thresholds shift in COPD; trends and the clinical picture matter more than 105 exactly.
Can RSBI be gamed by the ventilator?
Yes, which is why measurement conditions matter. Pressure support augments tidal volume and lowers the index artificially; the trial must be near-unsupported. An RSBI measured on full support describes the machine, not the patient.
What is a spontaneous breathing trial?
A 30 to 120 minute period of minimal support testing whether the patient sustains independent breathing. RSBI is typically measured during it. Passing the trial plus meeting extubation criteria leads to extubation; failing leads to rest and another trial tomorrow.
Does a good RSBI guarantee extubation success?
No. About 10 to 20 percent of patients with favorable RSBI still fail extubation, usually from secretion burden, weak cough, or upper airway edema. RSBI tests weaning endurance; the airway assessment tests extubation safety. Both must pass.
What raises RSBI falsely?
Pain, fever, anxiety, acidosis, and small endotracheal tubes all raise rate or shrink tidal volume independent of weaning readiness. Treat the confounder and remeasure rather than acting on a noisy number.
Who are Yang and Tobin?
Karl Yang and Martin Tobin, who published the index in the New England Journal of Medicine in 1991 from weaning trials. Their 105 threshold became one of the most cited numbers in critical care.
How often should weaning be reassessed?
Daily, with protocolized screening of readiness criteria each morning. Prolonged ventilation without daily weaning assessment is a classic ICU systems failure. RSBI is remeasured with each formal trial.