Rapid Shallow Breathing Index (RSBI) also known as Tobin Index is the ratio determined by the frequency (f) divided by the tidal volume (Vt) in liters during a Spontaneous Breathing Trail (SBT). The SBT is done while while the patient is intubated. An RSBI < 105 breaths/min/L has been widely accepted by healthcare professionals as a criteria for weaning to extubation. Whereas patients with RSBI > 105 will have a high chance of failure and require re-intubation.

As an example, a patient who has a respiratory rate of 20 breaths/min and a tidal volume of 400 mL/breath has an RSBI of (20 breaths/min)/(0.40 L) = 50 breaths/min/L.

How to Calculate Rapid Shallow Breathing Index (RSBI)

Respiratory Rate (f):
Tidal Volume (Vt) in Liters:
RSBI: breaths/min/L

What does Rapid Shallow Breathing Index of less than 105 Mean? An RSBI score of less than 105 is generally considered as an indication of weaning readiness.

Rapid Shallow Breathing Index


Once a patient passes a spontaneous breathing trail other considerations before extubation will need to be considered.

  • Does the patient have a difficult airway?
  • Is the patient able to clear secretions effectively?
  • Is there a risk for post-extubation laryngeal edema?