Rapid Shallow Breathing Index Calculator

Rapid Shallow Breathing Index Calculator for Critical Care. The historical threshold of 105 is context dependent and does not guarantee successful extubation below it or failure above it. Interpret the ratio alongside the actual liberation assessment rather than treating a favorable number as evidence of airway competence.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

RSBI divides respiratory frequency in breaths per minute by tidal volume expressed in liters. The repaired tool converts a volume entered in mL to liters before division and requires both measurements to be positive and finite. The output is a ratio, not an extubation authorization.

When to use this calculator

Use RSBI for learning about a recorded breathing pattern, with the measurement conditions documented. AARC's 2024 guideline states that RSBI is not required to determine readiness for a spontaneous breathing trial. An SBT and an assessment of airway protection answer additional questions.

Inputs used

  • Respiratory rate (/min)
  • Tidal volume (L)

Clinical interpretation

The historical threshold of 105 is context dependent and does not guarantee successful extubation below it or failure above it. Interpret the ratio alongside the actual liberation assessment rather than treating a favorable number as evidence of airway competence.

Worked example

Respiratory rate 24 with tidal volume 0.4 L gives 24 / 0.4 = 60 breaths/min/L. Rate 32 with volume 250 mL gives 32 / 0.25 = 128. Rate 21 with 0.2 L gives exactly 105 without a pass/fail label.

Limitations and safety notes

Ventilatory assistance, timing, fatigue and measurement technique can change the recorded pattern. The calculator cannot assess secretions, cough, mental status or upper-airway risk. A zero respiratory rate is rejected instead of being displayed as a favorable weaning result.

Frequently asked questions

Does RSBI below 105 clear extubation?

No. It does not replace clinical assessment, an appropriate SBT or evaluation of airway protection.

Can tidal volume be entered in mL?

Yes. The unit selector converts mL to liters, including when switching an already entered value.

Is RSBI required before an SBT?

The cited AARC 2024 guideline says it is not required to determine SBT readiness.

References

  • 2024 guideline: RSBI is not required for SBT readiness; liberation assessment is not an RSBI pass/fail test. https://www.aarc.org/wp-content/uploads/2023/11/CPG2024SpontaneousBreathingTrial.pdf
  • Original RSBI frequency/tidal-volume construct and historical105 threshold, not an unconditional extubation guarantee. https://www.nejm.org/doi/abs/10.1056/NEJM199105233242101

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 9, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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