Rapid Shallow Breathing Index (RSBI) Calculator

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The spontaneous breathing rate measured during a spontaneous breathing trial (SBT) or T-piece trial - typically assessed without ventilator assistance for one minute.
breaths/min
The volume of air moved in a single breath. Measured at the bedside with a spirometer or read from the ventilator display. Normal resting tidal volume is about 400-600 mL (0.4-0.6 L) in adults.
mL
COPD patients may generate deceptively low RSBI values despite impaired respiratory mechanics. Selecting COPD applies a modified threshold of 85 breaths/min/L.
RSBIHighly favorable
40breaths/min/L

Respiratory rate divided by tidal volume in litres

Extubation threshold105 breaths/min/L (classic Yang-Tobin)
Weaning readinessHighly favorable - strong predictor of weaning success
Tidal volume (L)0.45L
40 breaths/min/L
Highly favorable<65Favorable65-105Unfavorable105-130Failure likely130+

RSBI is 40.0 breaths/min/L - highly favorable for extubation.

  • The RSBI formula divides respiratory rate (18 breaths/min) by tidal volume (0.450 L), giving 40.0 breaths/min/L.
  • An RSBI below 65 is the most reassuring range and is associated with a very high probability of successful extubation in most patient populations.
  • RSBI alone has moderate sensitivity (83%) and poor specificity (58%) in meta-analyses. Always combine it with mental status, secretion burden, cough strength, hemodynamic stability, and oxygenation before deciding to extubate.

Next stepIf other readiness criteria are met (adequate oxygenation on low FiO2/PEEP, responsive and cooperative, manageable secretions, hemodynamically stable), proceed with a formal spontaneous breathing trial and extubation assessment.

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