If a patient is breathing spontaneously at a rate of 20 per minute with a tidal volume of 500 mL, what is their rapid-shallow breathing index (RSBI)?

• A. 0.025
• B. 0.04
• C. 40
• D. 25

Answer: (C)

To calculate the rapid-shallow breathing index (RSBI), you divide the respiratory rate (breaths per minute) by the tidal volume (in liters). The formula for RSBI is:

RSBI = Respiratory Rate (bpm) / Tidal Volume (L)

In this scenario, the patient is breathing at a rate of 20 breaths per minute with a tidal volume of 500 mL. To use the formula, it's important to convert the tidal volume from milliliters to liters:

500 mL = 0.5 L

Now, applying this to the RSBI formula:

RSBI = 20 breaths/min / 0.5 L = 40

Thus, the computed RSBI is 40, which indicates a certain level of respiratory efficiency. A higher RSBI may suggest respiratory distress or failure, while a lower RSBI can indicate effective breathing patterns. Understanding RSBI is crucial for assessing respiratory function in clinical settings, making the answer of 40 the appropriate outcome.