The RSBI is defined as the ratio of respiratory frequency to tidal volume (f/VT).
Measurement is done with a handheld spirometer attached to the endotracheal tube while a patient breathes room air for one minute without any ventilator assistance.
The concept was introduced in a 1991 paper by physicians Karl Yang and Martin J. Tobin from the University of Texas Health Science Center at Houston and Stritch School of Medicine at Loyola University in Chicago.
[4] Other criteria that have been suggested for a successful weaning trial include the ability to (1) tolerate a Spontaneous breathing trial for 30 minutes (in most patients, SBT failure will occur within approximately 20 minutes), (2) maintain a respiration rate of less than 35/min, and (3) keep an oxygen saturation of 90% without arrhythmias; sudden increases in heart rate and blood pressure; or development of respiratory distress, diaphoresis, or anxiety.
Patients should be assessed daily for their readiness to be weaned from mechanical ventilation by withdrawing sedation and performing a spontaneous breathing trial.