The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

USING VENTILATOR DERIVED RSBI AND TI/TTOT AS INDICATORS FOR SUCCESSFUL LIBERATION FROM MECHANINAL VENTILATION

Brian Timon BS RRT, Raymond Wolff Jr. RRT, Jennifer Ma BS RRT, Ken Hargett BS RRT The Methodist Hospital, Respiratory Care Services, Houston, TX.


Background:
The best approach to wean a patient from mechanical ventilation is always a hot topic and is highly debatable. There are several parameters used by clinicians to help us decide how soon a patient can be liberated from a ventilator. Current literature indicates that a Rapid Shallow Breathing Index (RSBI) of < 105 BPM/L is one parameter that suggests a high probability of a successful discontinuation from mechanical ventilation. Another parameter currently being used is the Inspiratory Time to Total Time Ratio (TI/TTOT), which is an indicator of diaphragmatic fatigue. Literature suggests that a TI/TTOT range of 0.30 to 0.50 indicates a high probability of successful liberation from a ventilator. We compared the RSBI and the TI/TTOT both derived automatically on the ventilator to validate these numbers in a group of surgical patients.

Method:
Data was collected from 47 post-operative CVICU patients that were weaned from controlled mechanical ventilation utilizing an approved protocol. The protocol incorporated a spontaneous breathing trial using Tubing Compensation (TC) of 100% on the Nellcor Puritan Bennett 840 Ventilator. Before extubating these patients, we observed the ventilator calculated RSBI and TI/TTOT and entered them into a database. We followed the patients for 24 hours to see how well they tolerated liberation from mechanical ventilation and to observe any possible reintubations.

RESULTS:
The RSBI for all of the patients we reviewed was below 105 BPM/L with a high of 84, a low of 15, and a mean of 46.3 BPM/L. The TI/TTOT was below 0.50 in all of our patients studied with a high of 0.48 and a low of 0.23 and a mean of 0.33. One of the patients had to be reintubated in the 24 hour post extubation period for excessive bleeding that required a trip back to the OR. This reintubation was not for impending respiratory failure or distress. The mean RSBI and TI/TTOT for coronary artery bypass surgery (CAB) was 44.5 BPM/L and 0.33 respectively. The mean RSBI and TI/TTOT for mitral and/or atrial valve replacement surgery (MVR/AVR) was 48.4 BPM/L and 0.36 respectively. See Table below for results. 

Surgery (n) Mean RSBI Mean TI/TTOT # Of Reintubations
CAB (30) 44.5 0.33 0
MVR/AVR (10) 48.4 0.36 0
Misc. Thoracotomy (7) 50.9 0.32 1*


 *Excessive bleeding was cause for reintubation


Conclusions:
Newer ventilators have more options and have the ability to give valuable information for bedside clinicians. In this study, we were able to use this information to determine a patient's readiness to be liberated from mechanical ventilation. An RSBI of < 105 BPM/L and a TI/TTOT of < 0.50, as determined by the ventilator, both appear to be valid predictors of successful discontinuation from mechanical ventilation in post CV surgery patients.

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