RSBI Calculator — Rapid Shallow Breathing Index
The Rapid Shallow Breathing Index (RSBI) divides the spontaneous respiratory rate by the tidal volume in litres. A score below 105 breaths/min/L predicts successful weaning from mechanical ventilation; 105 or above predicts failure.
breaths/min
mL
Cut-off: < 105 predicts successful extubation (Yang & Tobin 1991)
- 1
Tidal volume in litres
400 ÷ 1000 = 0.4 - 2
RSBI
20 ÷ 0.4 = 50Respiratory rate divided by tidal volume in litres; < 105 predicts weaning success.
How does this calculator work?
RSBI = respiratory rate (breaths/min) ÷ tidal volume (L). The landmark Yang & Tobin (1991) cut-off is 105 breaths/min/L: below 105 predicts weaning success, 105 or above predicts failure. Measure both values during a spontaneous breathing trial; combine RSBI with clinical assessment before extubating.
Formula
How this is calculated
The RSBI was introduced by Yang and Tobin in their landmark 1991 New England Journal of Medicine study as a simple, bedside measure of weaning readiness. It captures the tendency toward rapid, shallow breathing that characterises patients who struggle to breathe independently after prolonged mechanical ventilation. A patient who breathes 20 times per minute with an average tidal volume of 400 mL (0.4 L) has an RSBI of 50 breaths/min/L — well within the favourable range.
To measure RSBI, allow the patient to breathe spontaneously on a T-piece or a low level of pressure support. Count the respiratory rate (breaths per minute) and simultaneously measure the average exhaled tidal volume (in mL) over at least one minute. Convert the tidal volume to litres by dividing by 1,000, then divide the respiratory rate by that value. The result is the RSBI.
The original study found a cut-off of 105 breaths/min/L: values below 105 predicted successful extubation with a sensitivity of 97% and specificity of 64%. In subsequent studies sensitivity has remained high (around 80–95%) but specificity varies widely (50–75%) across different populations and ventilator settings. RSBI should be interpreted alongside other weaning criteria — oxygenation, secretion management, haemodynamic stability, and the physician's clinical judgement.
Frequently asked questions
Healthy adults at rest typically have an RSBI of 20–40 breaths/min/L, reflecting a rate of around 12–16 breaths/min and a tidal volume of 400–600 mL. Values below 80 are strongly associated with successful extubation; above 105 with failure.
Measure RSBI after at least 30 minutes on a spontaneous breathing trial (T-piece or low-pressure support). The patient should be awake, haemodynamically stable, and on ≤ 50% FiO₂ with PEEP ≤ 8 cmH₂O.
No. RSBI has good sensitivity but modest specificity. Clinicians combine it with oxygenation (PaO₂/FiO₂ ratio), cough strength, secretion burden, mental status, and haemodynamic stability to make extubation decisions. No single index is sufficient alone.
Also known as
TG we-Calculate Editorial Team. (2026). RSBI Calculator — Rapid Shallow Breathing Index [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/rsbi-calculator
TG we-Calculate Editorial Team. "RSBI Calculator — Rapid Shallow Breathing Index." TG we-Calculate. 2026. https://we-calculate.com/calculator/rsbi-calculator.
TG we-Calculate Editorial Team, "RSBI Calculator — Rapid Shallow Breathing Index," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/rsbi-calculator
@misc{wecalculate_rsbi_calculator, title = {RSBI Calculator — Rapid Shallow Breathing Index}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/rsbi-calculator}}, year = {2026}, note = {TG we-Calculate} }
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