Q: What is the right step just prior to obtaining the Rapid Shallow Breathing Index (RSBI)?
RSBI is the ratio of respiratory frequency/rate to tidal volume (f/VT). It is not a perfect but a good indicator of a patient's successful liberation from the ventilator. It has been suggested that a reliable RSBI can be obtained by measuring respiratory rate and tidal volume, using a hand-held spirometer attached to the endotracheal tube (ETT), while a patient is breathing room air for one minute without any ventilator assistance. All new models of ventilators are equipped to measure RSBI.
Yang KL, Tobin MJ. A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. N Engl J Med 1991; 324:1445.