Calculate the Rapid Shallow Breathing Index (f/VT) for ventilator weaning assessment. Includes weaning readiness checklist, P/F ratio, and predictive performance data.
The Rapid Shallow Breathing Index (RSBI), introduced by Yang and Tobin in 1991, is the most widely used predictor of ventilator weaning success. Calculated as the ratio of respiratory rate to tidal volume (f/VT) during a spontaneous breathing trial (SBT), it quantifies the patient's breathing pattern efficiency — a high RSBI indicates rapid, shallow breathing that is unsustainable.
An RSBI below 105 breaths/min/L predicts successful weaning with a sensitivity of 97% and specificity of 64%, making it excellent for ruling out weaning failure (high negative predictive value). The index is measured during a 1-minute observation of unassisted breathing (T-piece trial or minimal pressure support) after routine SBT prerequisites are met.
This calculator computes RSBI alongside complementary weaning parameters: minute ventilation, PaO₂/FiO₂ ratio, tidal volume per kilogram, and a comprehensive weaning readiness checklist. Together, these parameters provide a structured framework for the complex clinical decision of when to extubate a mechanically ventilated patient.
Ventilator weaning decisions have profound consequences — premature extubation can cause reintubation (associated with increased mortality), while delayed extubation prolongs ICU stay, increases VAP risk, and adds costs. RSBI provides a quantitative, reproducible parameter that structures the otherwise subjective weaning assessment, helping clinicians identify the optimal extubation window. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain.
RSBI = Respiratory Rate (breaths/min) / Tidal Volume (L) Threshold: < 105 predicts successful weaning Minute Ventilation = RR × VT P/F Ratio = PaO₂ / FiO₂ (as fraction)
Result: RSBI = 62.9 breaths/min/L — below threshold, ~95% weaning success
RSBI = 22 / 0.35 = 62.9, well below the threshold of 105. P/F ratio = 85/0.40 = 213. Minute ventilation = 7.7 L/min. All parameters pass the weaning readiness checklist, predicting high likelihood of successful extubation.
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Disconnect the patient from the ventilator or set minimal support (CPAP 0, PS 0 or T-piece). Wait at least 1 minute for the breathing pattern to stabilize. Measure the average respiratory rate and tidal volume over that minute. RSBI = RR ÷ VT (in liters).
The classic threshold is < 105 breaths/min/L. However, some ICUs use more conservative thresholds (< 80) for higher confidence. Below 80, extubation success is approximately 95%. Above 130, weaning almost always fails.
Yes. A low RSBI does not guarantee extubation success because it does not assess cough strength, upper airway patency, secretion volume, or mental status — all of which affect post-extubation respiratory function. RSBI predicts ability to breathe, not ability to protect the airway.
T-piece trials are considered more rigorous (no pressure support). RSBI measured on CPAP/PS may appear lower than on T-piece. The original Yang-Tobin study used T-piece. If using CPAP, consider a slightly lower threshold (< 80).
RSBI can be measured after 1 minute of spontaneous breathing. The full SBT typically lasts 30–120 minutes. If RSBI is borderline at 1 minute, reassess at 30 minutes — deterioration suggests weaning failure.
Prerequisites before SBT: FiO₂ ≤ 40%, PEEP ≤ 5–8, hemodynamic stability, adequate mental status, cough and gag present. During SBT: respiratory rate, heart rate, SpO₂, blood pressure, work of breathing, patient comfort, and ABG at the end.