What are the criteria for extubation using the Rapid Shallow Breathing Index (RSBI) in a patient with underlying respiratory or cardiac conditions?

Extubation Criteria Using RSBI

An RSBI (Rapid Shallow Breathing Index) ≤105 breaths/min/L measured during spontaneous breathing is the established threshold for predicting successful extubation, though this must be combined with assessment of upper airway patency, cough effectiveness, and secretion management—particularly in patients with underlying cardiac or respiratory conditions who face higher extubation failure rates. 1, 2

RSBI Measurement Technique

The RSBI should be measured correctly to ensure validity:

• Calculate RSBI as respiratory rate divided by tidal volume (in liters) during spontaneous breathing with PSV=0 and PEEP=0 3
• Do not measure during the first minute of spontaneous breathing, as respiratory drive may still be suppressed; wait until a steady-state is achieved 1
• For high-risk patients, measure RSBI at both 5 minutes and 120 minutes during the spontaneous breathing trial (SBT) 4
• The rate of change between these measurements (ΔRSBI) provides additional predictive value 5, 4

RSBI Thresholds and Predictive Values

Standard Threshold

• RSBI ≤105 breaths/min/L predicts successful extubation with a positive predictive value of 0.78 and negative predictive value of 0.95 1
• The likelihood ratio for RSBI <80 is 7.53, meaning successful weaning is 7.53 times more likely than failure 1
• RSBI >105 is associated with need for intubation in patients receiving noninvasive ventilation 1

Enhanced Predictive Accuracy with Serial Measurements

• RSBI measured at 120 minutes (RSBI-120) ≤70-73 breaths/min/L provides superior accuracy (82-89%) compared to single early measurements 4
• A rate of change (ΔRSBI) ≤-3% between 5 and 120 minutes increases likelihood of successful extubation by 3.4 times 5
• Using both RSBI-120 ≤72 AND ΔRSBI ≤-3 together increases successful extubation likelihood by 28.48 times 5

Special Considerations for Cardiac and Respiratory Conditions

Patients with Underlying Respiratory Disease

• In patients with airway disease (COPD, asthma), use RSBI threshold of ≤73 breaths/min/L at 120 minutes with 83% accuracy 4
• In patients with parenchymal disease, use RSBI threshold of ≤71 breaths/min/L at 120 minutes with 88% accuracy 4
• RSBI >105 during NIV predicts need for intubation with 55% requiring intubation versus 31% with RSBI ≤105 6

Patients with Cardiac Conditions

• Approximately 20% of patients with RSBI <100 still fail extubation, primarily due to congestive heart failure, upper airway obstruction, or new pulmonary processes rather than respiratory muscle failure 7
• These patients require additional assessment beyond RSBI alone 7

Gender and Endotracheal Tube Size

• Women have higher RSBI values than men, independent of body size 1
• Women with narrow endotracheal tubes (≤7mm) have especially high false-negative rates, requiring clinical judgment beyond the numerical threshold 1

Critical Pitfalls and Additional Assessment Requirements

RSBI Limitations

RSBI alone is insufficient for extubation decisions—the false-positive rate of approximately 20% occurs because RSBI cannot predict:

• Upper airway obstruction or laryngeal edema 7
• Congestive heart failure 7
• Aspiration risk 7
• Encephalopathy or altered mental status 7
• New pulmonary processes 7

Mandatory Additional Assessments Before Extubation

Perform cuff leak test in patients with risk factors (prolonged intubation >48 hours, difficult intubation, large ETT, high cuff pressures):

• Absolute leak volume <110 mL or relative leak volume <10% indicates high risk for post-extubation stridor 2
• Consider corticosteroids (prednisolone 1 mg/kg/day) started at least 6 hours before extubation if cuff leak is inadequate 1, 2

Assess cough effectiveness and secretion management:

• Ineffective cough or excessive tracheobronchial secretions increase extubation failure risk 2
• Physiotherapist presence during extubation is recommended for high-risk patients to manage immediate complications like bronchial obstruction 1, 2

Verify adequate mental status:

• Patient should be awake with eye opening and response to commands 2
• Adequate mental status to protect airway is essential 2

Confirm hemodynamic stability:

• Absence of significant hypotension or need for high-dose vasopressors 2

Risk Stratification Algorithm

High-Risk Patients (20-30% reintubation rate)

Patients with any of the following:

• Age >65 years 1
• Chronic cardiac or respiratory disease 1, 2
• Prolonged mechanical ventilation >14 days 2
• Hypercapnia during SBT 1
• Previously failed extubation 2

For high-risk patients:

• Use prophylactic NIV (not HFNC) immediately after extubation for 24-48 hours, especially if hypercapnic 1, 2
• Consider extubation with airway exchange catheter 2
• Ensure physiotherapist availability 1, 2

Standard-Risk Patients (15% reintubation rate)

• High-flow nasal cannula is appropriate for hypoxemic patients at low risk 1, 2
• Standard post-extubation monitoring 1

Warning Signs During NIV After Extubation

If noninvasive support is used post-extubation, monitor for deterioration:

• Tidal volumes persistently >9.5 mL/kg predicted body weight suggest need for reintubation 1
• RSBI >105 during NIV is associated with need for intubation 1
• Lack of substantial improvement in gas exchange and respiratory rate within a few hours mandates reintubation 1
• Delayed intubation is associated with increased mortality—do not hesitate if patient deteriorates 1