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MEDICALPulmonaryHealth Calculator
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R S B I
Patient with favorable weaning parameters
Understanding R S B IUse the calculator below to check your health metrics
Why This Health Metric Matters
Why: This calculation helps assess important health parameters for clinical and personal wellness tracking.
How: Enter your values above and the calculator will apply validated formulas to compute your results.
- ●Evidence-based calculations
- ●Used in clinical settings worldwide
- ●Regular monitoring recommended
Sample Scenarios
Ready to Wean (RSBI <105)
Patient with favorable weaning parameters
Borderline (RSBI 80-105)
Patient requiring careful assessment
Not Ready (RSBI >105)
Patient with high risk of weaning failure
High RSBI (>150)
Significant respiratory distress during SBT
Young Post-Op Patient
Young healthy patient recovering from surgery
Enter SBT Parameters
RSBI Components
Ventilator
Patient
⚠️For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
🏥 Health Facts
— WHO
— CDC
What is RSBI?
The Rapid Shallow Breathing Index (RSBI) is a simple calculation that predicts success of weaning from mechanical ventilation. It is the ratio of respiratory rate to tidal volume (f/VT), measured during spontaneous breathing. An RSBI less than 105 breaths/min/L suggests the patient is likely to tolerate extubation successfully.
RSBI <80
High likelihood of successful extubation (>80%)
RSBI 80-105
Moderate success rate (60-80%)
RSBI >105
Higher risk of weaning failure
Historical Background
- • 1991: Yang and Tobin published landmark NEJM study
- • Study design: Prospective evaluation of 100 medical ICU patients
- • Findings: RSBI was the best single predictor of weaning success
- • Threshold: f/VT <105 identified for optimal sensitivity/specificity
- • Impact: Became most widely used weaning predictor worldwide
The Original Yang-Tobin Study (1991)
- • Patients: 100 medical ICU patients requiring ventilator weaning
- • Measurements: Multiple indices compared (MIP, PImax, VT, f, etc.)
- • RSBI cutoff: <105 breaths/min/L
- • Sensitivity: 97% (excellent for ruling out failure)
- • Specificity: 64%
- • PPV: 78%, NPV: 95%
How to Measure RSBI
- Place patient on minimal support (T-piece, CPAP 5, or PSV 5-8)
- Allow 1-2 minutes for patient to stabilize
- Measure respiratory rate (count for 1 minute)
- Measure tidal volume (average of several breaths)
- Calculate RSBI = RR / VT (in liters)
- Interpret: <105 favorable, ≥105 unfavorable
RSBI Interpretation Thresholds
| RSBI Value | Interpretation | Success Rate |
|---|---|---|
| <80 | Excellent candidate | >80% |
| 80-105 | Good candidate | 60-80% |
| 105-150 | Borderline | 30-60% |
| >150 | High failure risk | <30% |
Spontaneous Breathing Trial (SBT) Methods
T-Piece Trial
- • No ventilator support
- • Patient breathes through circuit
- • Most challenging method
- • May identify marginal patients
CPAP Trial
- • CPAP 5 cmH2O
- • No pressure support
- • Maintains PEEP benefit
- • Common method
Low PSV Trial
- • PSV 5-8 cmH2O
- • Overcomes ETT resistance
- • May overestimate readiness
- • Easier for patients
Additional Weaning Parameters
- • P/F Ratio: >150-200 (adequate oxygenation)
- • PEEP: ≤8 cmH2O (FiO2 ≤40%)
- • MIP (PImax): ≤-20 to -25 cmH2O (respiratory muscle strength)
- • Vital Capacity: >10-15 mL/kg
- • Minute Ventilation: <10-15 L/min
- • Hemodynamics: Stable, minimal/no vasopressors
- • Mental Status: Awake, follows commands
Pre-SBT Readiness Checklist
- • ☐ Resolution/improvement of underlying cause
- • ☐ Adequate oxygenation (P/F >150, PEEP ≤8, FiO2 ≤40%)
- • ☐ Hemodynamically stable (no/minimal vasopressors)
- • ☐ No significant fever or ongoing sepsis
- • ☐ Adequate hemoglobin (Hb >7-8 g/dL)
- • ☐ Appropriate mental status (GCS >8, follows commands)
- • ☐ Adequate cough and gag reflexes
- • ☐ Manageable secretions
- • ☐ No planned procedures requiring sedation
SBT Failure Criteria
- • Respiratory distress: RR >35, accessory muscle use
- • Desaturation: SpO2 <90% or PaO2 <60
- • Hemodynamic instability: HR >140 or <50, SBP <90 or >180
- • Arrhythmias: New significant arrhythmias
- • Altered mental status: Agitation, diaphoresis, anxiety
- • pH <7.32: Respiratory acidosis
Post-Extubation Care
- • Oxygen: Start with supplemental O2 (nasal cannula or mask)
- • Monitoring: Close observation for 24-48 hours
- • NPO: Keep NPO initially, evaluate swallowing
- • Secretion management: Encourage coughing, suctioning if needed
- • High-risk patients: Consider prophylactic NIV
- • Stridor: Watch for laryngeal edema, have epinephrine ready
RSBI Limitations
- • Population-specific: Originally validated in medical ICU patients
- • Elderly: May have higher RSBI at baseline
- • COPD: Chronic hyperinflation affects breathing pattern
- • Neurological: Altered respiratory drive affects RSBI
- • Doesn't assess: Cough, secretions, airway protection, mental status
- • Timing: Early measurement may be inaccurate
RSBI in Special Populations
COPD Patients
- • May tolerate higher RSBI values
- • Consider RSBI up to 130
- • Use with NIV backup plan
- • Assess for hyperinflation
Neurological Patients
- • Airway protection more important
- • GCS and cough strength critical
- • May need tracheostomy
- • RSBI less predictive
Cardiac Patients
- • Watch for weaning-induced pulmonary edema
- • Optimize fluid status before SBT
- • Consider echo to assess LV function
- • May benefit from diuresis
Elderly Patients
- • Decreased respiratory muscle reserve
- • May fail despite favorable RSBI
- • Consider extended SBT
- • Higher reintubation rates
Clinical Pearls
- • Best use: RSBI is best for ruling OUT failure (high NPV)
- • Not definitive: Low RSBI doesn't guarantee success
- • Context matters: Use with clinical assessment, not alone
- • Early measurement: Wait 1-2 minutes into SBT for accurate reading
- • Trending: Worsening RSBI during SBT is concerning
Causes of Weaning Failure
Respiratory Causes
- • Unresolved pulmonary disease
- • Excessive secretions
- • Bronchospasm
- • Upper airway obstruction
- • Respiratory muscle weakness
Cardiovascular Causes
- • Cardiac ischemia
- • Heart failure / fluid overload
- • Arrhythmias
- • Weaning-induced pulmonary edema
- • Hemodynamic instability
Neurological/Psych
- • Encephalopathy / delirium
- • Over-sedation
- • ICU-acquired weakness
- • Anxiety / panic
- • Inadequate sleep
Metabolic/Other
- • Electrolyte abnormalities (K, Mg, PO4)
- • Severe anemia
- • Malnutrition
- • Thyroid dysfunction
- • Ongoing infection/sepsis
Role of NIV After Extubation
- • Prophylactic NIV: For high-risk patients (COPD, CHF, elderly, prolonged MV)
- • Evidence: Reduces reintubation rates in high-risk groups
- • Timing: Apply immediately post-extubation
- • Duration: At least 24-48 hours, then wean
- • Not for rescue: NIV for post-extubation failure has mixed results
Cuff Leak Test
- • Purpose: Assess for laryngeal edema before extubation
- • Method: Deflate cuff, measure tidal volume difference
- • Positive leak: >110 mL or >12-24% of inspired VT
- • Absent leak: Risk of post-extubation stridor
- • High-risk patients: Prolonged intubation, traumatic intubation, self-extubation
- • Treatment: Consider steroids before extubation if no leak
ICU-Acquired Weakness and Weaning
- • Prevalence: 25-50% of ICU patients with >7 days mechanical ventilation
- • Risk factors: Sepsis, steroids, prolonged immobility, hyperglycemia
- • Impact: Prolongs weaning, increases mortality
- • Assessment: MRC score, hand grip strength
- • Prevention: Early mobilization, avoid hyperglycemia, minimize sedation
Daily Awakening and SBT Protocol (ABC Bundle)
- • SAT: Daily Spontaneous Awakening Trial (sedation interruption)
- • SBT: Daily Spontaneous Breathing Trial if SAT passes
- • Evidence: Reduces duration of mechanical ventilation
- • Safety: Can be performed safely in most patients
- • Coordination: Requires RT, nursing, and physician collaboration
RSBI Quick Facts
- • Formula: RSBI = RR / VT (in liters)
- • Threshold: <105 breaths/min/L
- • Sensitivity: 97%
- • Specificity: 64%
- • NPV: 95%
- • Best use: Ruling OUT weaning failure
Clinical Scenario Examples
Scenario 1: Post-Surgical Patient
40-year-old post abdominal surgery. RR 16, VT 500 mL. RSBI = 32. Excellent candidate - proceed with SBT and likely extubation.
Scenario 2: COPD Exacerbation
68-year-old with COPD exacerbation. RR 24, VT 320 mL. RSBI = 75. Favorable, but given COPD, ensure NIV available post-extubation.
Scenario 3: ARDS Recovery
55-year-old recovering from ARDS. RR 28, VT 280 mL. RSBI = 100. Borderline - consider extended SBT, close monitoring. May still succeed.
Key Formulas
- RSBI: RR (breaths/min) / VT (Liters)
- Success threshold: RSBI <105 breaths/min/L
- Minute Ventilation: RR × VT
- P/F Ratio: PaO2 / FiO2
RSBI Calculator Summary
Formula
RR/VT
Threshold
<105
Sensitivity
97%
Best Use
Rule out failure
Documentation Guide
- • SBT method: T-piece, CPAP, or PSV level
- • Duration: Time of SBT when RSBI measured
- • Vital signs: RR, HR, BP, SpO2 during SBT
- • RSBI value: Document calculation
- • Tolerance: Signs of distress or stability
- • Decision: Proceed with extubation or continue MV
Key References
Yang & Tobin (1991)
A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. NEJM 324:1445-1450.
Esteban et al. (1999)
Characteristics and outcomes in adult patients receiving mechanical ventilation. A 28-day international study. JAMA 281:324-329.
Girard et al. (2008)
Efficacy and safety of a paired sedation and ventilator weaning protocol (ABC Protocol). Lancet 371:126-134.
Memory Aids
- • "105 to survive" - RSBI <105 for successful weaning
- • "Rapid and Shallow = Bad" - High RR/low VT = high RSBI
- • "Rule OUT, not IN" - Best for excluding failure (high NPV)
- • "f over V" - Frequency over Volume (in liters)
Key Takeaways
- • RSBI = RR / VT (in liters) - simple bedside calculation
- • Threshold: RSBI <105 predicts weaning success
- • High NPV (95%): Low RSBI helps rule out failure
- • Use with other criteria (oxygenation, hemodynamics, mental status)
- • Special populations (COPD, elderly) may need adjusted interpretation
- • Consider NIV backup for high-risk patients
Important Disclaimer
RSBI is one of many factors in weaning decisions. This calculator is for educational purposes and clinical decision support. Extubation decisions should involve comprehensive assessment including clinical judgment, additional weaning parameters, and consideration of patient-specific factors. Always follow institutional protocols and consult with the care team.
Ventilator Weaning Protocols
Protocol-Driven Weaning
- • RT and nurse-led protocols
- • Daily screening for SBT readiness
- • Standardized criteria reduce MV duration
- • Physician notification when ready
Physician-Directed
- • Individualized assessment
- • Complex patients benefit
- • May delay weaning attempts
- • Requires active daily assessment
Pressure Support Ventilation (PSV) Weaning
- • Starting level: PSV that achieves comfortable breathing (usually 15-20 cmH2O)
- • Reduction: Decrease by 2-4 cmH2O increments
- • Target: PSV 5-8 cmH2O (overcomes ETT resistance)
- • Frequency: 1-3 times daily based on tolerance
- • Monitoring: RR, VT, signs of distress with each change
SIMV Weaning (Less Preferred)
- • Method: Gradually reduce mandatory breath rate
- • Problems: Prolongs weaning compared to SBT/PSV
- • Evidence: Studies show longer MV duration with SIMV weaning
- • Current practice: SBT or PSV weaning preferred
- • May use: Selected patients who struggle with SBT
Prolonged Mechanical Ventilation
- • Definition: Mechanical ventilation >21 days (≥6 hours/day)
- • Prevalence: ~10% of ventilated patients
- • Tracheostomy: Consider at 7-14 days if prolonged MV expected
- • LTAC transfer: May benefit from specialized weaning facilities
- • Goals of care: Discuss prognosis and preferences early
Tracheostomy Considerations
- • Timing: Early (≤7 days) vs late tracheostomy remains debated
- • Benefits: Patient comfort, oral care, mobility, secretion management
- • Weaning advantages: Lower airway resistance, easier capping trials
- • Decannulation: Separate process from weaning off ventilator
- • Speaking valves: Allow communication, assess airway
Diaphragm Assessment
- • Diaphragm ultrasound: Measure thickness and thickening fraction
- • Thickening fraction: TF >30% suggests adequate diaphragm function
- • Diaphragm excursion: >1 cm suggests preserved function
- • VIDD: Ventilator-induced diaphragm dysfunction is common
- • Prevention: Maintain some spontaneous breathing, early mobilization
Fluid Management and Weaning
- • Fluid status: Excessive fluid complicates weaning
- • Conservative fluid: May reduce MV duration in some patients
- • Weaning-induced pulmonary edema: Occurs when cardiac output increases
- • BNP: Rising BNP during SBT may predict cardiac cause of failure
- • Diuresis: Consider before SBT in fluid-overloaded patients
Sedation and Delirium Impact
- • Over-sedation: Prolongs mechanical ventilation
- • Light sedation: RASS -2 to 0 allows participation in weaning
- • Delirium: Affects ability to cooperate, prolongs MV
- • CAM-ICU: Screen daily for delirium
- • ABCDEF bundle: Minimize sedation, promote early mobility
Nutrition and Weaning
- • Malnutrition: Impairs respiratory muscle function
- • Protein intake: Adequate protein supports muscle recovery
- • Overfeeding: Excess carbohydrate increases CO2 production
- • Phosphorus: Low phosphorus impairs diaphragm function
- • Enteral nutrition: Start early, continue during weaning
Comparison of Weaning Parameters
| Parameter | Threshold | Sensitivity | Specificity |
|---|---|---|---|
| RSBI | <105 | 97% | 64% |
| MIP/PImax | ≤-20 to -30 | ~80% | ~50% |
| VC | >10 mL/kg | ~75% | ~55% |
| RR | <35/min | ~90% | ~35% |
| VT | >5 mL/kg | ~85% | ~30% |
SBT Duration Controversy
- • 30-minute SBT: Commonly used, may be sufficient for many patients
- • 120-minute SBT: Traditional duration, may identify late failures
- • Evidence: 30-minute SBT appears equivalent to 120-minute in most patients
- • Longer trials: Consider for high-risk patients (COPD, CHF)
- • Early measurement: RSBI at 1-5 minutes may be predictive
Reintubation Considerations
- • Reintubation rate: 10-20% of extubated patients
- • Timing: Most reintubations within 48-72 hours
- • Causes: Respiratory failure, secretions, airway obstruction, aspiration
- • Risk factors: Prolonged MV, elderly, COPD, neurological impairment
- • Mortality: Reintubation associated with higher mortality
Definitions of Extubation Failure
- • Reintubation: Need for re-intubation within 24-72 hours
- • Post-extubation distress: Requiring NIV or high-flow oxygen
- • Tracheostomy: Need for tracheostomy post-extubation
- • Death: Related to extubation failure
High-Flow Nasal Cannula Post-Extubation
- • HFNC: Humidified oxygen at 30-60 L/min
- • Benefits: Small PEEP effect, comfort, airway humidification
- • Evidence: May reduce reintubation in low-risk patients
- • Comparison to NIV: Non-inferior for prevention of reintubation
- • High-risk patients: Consider NIV over HFNC
Common Questions
Why is RSBI better than individual parameters?
RSBI combines two parameters that together reflect the balance between respiratory demand (RR) and capacity (VT), providing better predictive value than either alone.
Can RSBI be measured on a ventilator?
RSBI should be measured during spontaneous breathing (T-piece, CPAP, or minimal PSV). It's not valid during controlled ventilation.
What if RSBI is >105 but patient looks comfortable?
Clinical assessment matters. Some patients (especially COPD) may succeed despite higher RSBI. Consider extended SBT with close monitoring.
RSBI Calculator Final Summary
The Rapid Shallow Breathing Index (RSBI) is a validated, easy-to-calculate bedside tool for predicting weaning success. With a threshold of <105 breaths/min/L, it has high sensitivity (97%) for identifying patients who can be successfully extubated. However, it should be used as part of a comprehensive weaning assessment including oxygenation, hemodynamics, neurological status, and airway protection. Daily SBT trials using protocol-driven weaning reduce duration of mechanical ventilation.
Formula
RR/VT
Threshold
<105
NPV
95%
Best Use
Exclude failure
Role of Respiratory Therapist
- • Daily screening: Assess readiness for SBT daily
- • SBT conduct: Set up and monitor spontaneous breathing trials
- • RSBI measurement: Measure and calculate RSBI during SBT
- • Communication: Report findings to physician team
- • Protocol implementation: Follow institutional weaning protocols
- • Documentation: Record all weaning parameters and patient response
Nursing Considerations
- • Sedation awakening: Perform daily sedation interruption (SAT)
- • Positioning: Elevate head of bed for SBT
- • Suctioning: Ensure airway clear before and during SBT
- • Monitoring: Close observation during spontaneous breathing
- • Comfort measures: Manage anxiety and distress
- • Family communication: Keep family informed of weaning progress
Quality Metrics for Weaning
- • Ventilator-free days: Days alive and off MV in 28-day period
- • Duration of MV: Time from intubation to successful extubation
- • Reintubation rate: Percentage requiring re-intubation within 48-72h
- • Daily SBT compliance: Percentage of eligible patients screened
- • Unplanned extubation rate: Self-extubation events
Pre-Extubation Checklist
- • ☐ SBT passed (30-120 minutes)
- • ☐ RSBI <105 (or acceptable for population)
- • ☐ Cuff leak present (or steroids given)
- • ☐ Patient awake and following commands
- • ☐ Adequate cough during suctioning
- • ☐ Secretions manageable
- • ☐ Hemodynamically stable
- • ☐ No planned procedures requiring sedation
- • ☐ NPO order placed
- • ☐ Post-extubation oxygen ready
- • ☐ NIV available if high-risk
- • ☐ Re-intubation equipment at bedside
Sample SBT Documentation Note
"SBT performed on CPAP 5 cmH2O for 30 minutes. RR 20/min, VT 380 mL. RSBI = 53 breaths/min/L. SpO2 98% on FiO2 0.4. HR 78 bpm, BP 128/76. No accessory muscle use or distress. Patient awake, follows commands, strong cough. Cuff leak present (150 mL). SBT passed. Recommend extubation."
Troubleshooting SBT Failure
Immediate Actions
- • Resume ventilatory support
- • Assess for reversible causes
- • Check electrolytes (K, Mg, PO4)
- • Evaluate fluid status (echo, BNP)
- • Address pain and anxiety
Next Steps
- • Treat underlying cause
- • Consider gradual PSV weaning
- • Optimize nutrition
- • Early mobilization
- • Re-attempt SBT in 24 hours
Additional Resources
- • Society of Critical Care Medicine (SCCM) Guidelines
- • American Thoracic Society (ATS) Weaning Guidelines
- • European Respiratory Society (ERS) / ESICM Guidelines
- • ICU Liberation Bundle (A-F)
- • ARDSNet Protocols
Step-by-Step Weaning Workflow
- Daily screening: Is patient ready for SBT? (readiness criteria)
- Perform SAT: Reduce/stop sedation, assess mental status
- If SAT passed: Proceed to SBT (T-piece, CPAP, or low PSV)
- Measure RSBI at 1-5 minutes of SBT
- Continue SBT for 30-120 minutes
- Monitor for failure criteria throughout
- If SBT passed: Assess airway (cuff leak, cough, secretions)
- Extubate if all criteria met
- Post-extubation: Apply supplemental O2, monitor closely
- If high-risk: Consider prophylactic NIV or HFNC
Quick Reference Card
| Parameter | Value |
|---|---|
| RSBI Formula | RR / VT (in liters) |
| Success threshold | <105 breaths/min/L |
| Excellent candidate | <80 breaths/min/L |
| Sensitivity | 97% |
| Specificity | 64% |
| NPV | 95% |
| PPV | 78% |
| Reference | Yang & Tobin, NEJM 1991 |
Final Clinical Note
RSBI is an excellent screening tool but should never be the sole determinant of extubation decisions. Clinical assessment, including mental status, airway protection, secretion management, and underlying condition resolution, remains essential. Protocol-driven daily SBT trials reduce mechanical ventilation duration and improve outcomes. When in doubt, extended observation or repeat SBT the following day is safer than premature extubation in borderline cases.
Integrative Weaning Assessment
- • RSBI: Best for ruling out weaning failure (screening)
- • Clinical assessment: Overall appearance, effort, distress
- • P/F ratio: Oxygenation adequacy
- • MIP/PImax: Respiratory muscle strength
- • Cough strength: Airway protection capability
- • Mental status: Ability to protect airway
- • Hemodynamics: Cardiac reserve for spontaneous breathing
Early Mobilization and Weaning
- • Evidence: Early mobilization reduces duration of MV
- • Benefits: Prevents ICU-acquired weakness, delirium
- • Safety: Can be performed safely even on ventilated patients
- • Progression: ROM → sitting → standing → walking
- • Team approach: PT, OT, nursing, respiratory therapy
Communication with Family
- • Explain weaning process: What SBT is and why it's important
- • Set realistic expectations: Weaning may take multiple attempts
- • Discuss risks: Possibility of reintubation
- • Include in goals of care: Especially if prolonged ventilation expected
- • Family presence: Can support patient during SBT
Special Circumstances
COVID-19 Patients
- • Often prolonged MV course
- • High rates of ICU-acquired weakness
- • Consider prone positioning effects
- • May need extended SBT observation
Obese Patients
- • Higher work of breathing
- • Atelectasis risk post-extubation
- • Consider HFNC or NIV backup
- • Semi-upright position important
Final Memory Aids
- • "f over V" - Frequency over Volume (in liters)
- • "105 threshold" - The magic number to remember
- • "SAT then SBT" - Sedation awakening before breathing trial
- • "NPV 95" - If low RSBI, 95% chance of success
- • "Rule out, not in" - Best for excluding failure
Clinical Workflow Summary
- Screen daily for weaning readiness
- Perform SAT (sedation interruption)
- If SAT passed, proceed to SBT
- Measure RSBI during SBT
- If RSBI <105 and SBT tolerated, assess airway
- If airway adequate, proceed with extubation
- Post-extubation: Apply oxygen, monitor closely
- If high-risk: Consider prophylactic NIV
RSBI Summary Table
| RSBI Range | Category | Action |
|---|---|---|
| <80 | Excellent | Proceed with extubation |
| 80-105 | Good | Consider extubation with assessment |
| 105-150 | Borderline | Address reversible factors, re-assess |
| >150 | Poor | Continue MV, investigate causes |
Important Safety Note
This RSBI Calculator is for educational and clinical decision support purposes. Extubation decisions involve complex clinical judgment and should always be made by qualified healthcare professionals considering the complete clinical picture.
- • Always follow institutional protocols and guidelines
- • RSBI is one of many factors in weaning decisions
- • Ensure adequate monitoring and backup plans before extubation
- • Have reintubation equipment immediately available
- • Consider prophylactic NIV for high-risk patients
Reference Values Quick Card
- • RSBI Threshold: <105 breaths/min/L
- • Excellent: <80 breaths/min/L
- • Sensitivity: 97%
- • Specificity: 64%
- • NPV: 95%
- • PPV: 78%
- • Original Study: Yang & Tobin, NEJM 1991
- • SBT Methods: T-piece, CPAP 5, PSV 5-8
- • Measurement Timing: 1-5 minutes into SBT
- • SBT Duration: 30-120 minutes
- • P/F Ratio Target: >150-200
- • PEEP Target: ≤8 cmH2O
- • FiO2 Target: ≤40-50%
- • Reintubation Rate: 10-20% overall
- • High-Risk Groups: COPD, CHF, elderly, prolonged MV
- • NIV Backup: Consider for high-risk patients
- • Cuff Leak Test: >110 mL or >12-24% of VT
- • MIP/PImax: ≤-20 to -30 cmH2O
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