weaning
RSBI = f ÷ VT (in liters)
Normal: < 105 breaths/min/L
Normal: 12–20 breaths/min
Normal: 0.4–0.6 L
The RSBI quantifies the balance between respiratory rate and tidal volume during spontaneous breathing. Patients in respiratory distress who are fatiguing tend to breathe rapidly and shallowly (high f, low VT) — producing a high RSBI. A low RSBI indicates the patient can take adequate breaths without tachypnea.
Measure during a spontaneous breathing trial (SBT) at the START of the trial (first 1–2 minutes on CPAP 0 or minimal PS 5 cmH2O). Used as a screening tool to predict extubation success. Should be combined with clinical assessment — RSBI alone is insufficient.
Ready to wean
→ 28 breaths/min/L
Excellent RSBI — strong predictor of successful extubation
Borderline
→ 88 breaths/min/L
Below 105 but concerning — assess clinical picture carefully
Likely to fail
→ 200 breaths/min/L
Very high RSBI — patient breathing rapidly and shallowly; likely not ready for extubation
RSBI < 105 combined with adequate mental status, ability to cough, manageable secretions, stable hemodynamics, and acceptable ABG = good extubation candidate. RSBI > 105 predicts failure (positive predictive value 95% for failure). RSBI was developed by Yang and Tobin in 1991 and remains the most widely used single weaning predictor.