The prediction of extubation success of postoperative neurosurgical patients using frequency-tidal volume ratios.
BACKGROUND
The process of discontinuing neurological patients from mechanical ventilation is still controversial. The aim of this study was to report the outcome from extubating patients undergoing elective craniotomy and correlate the result with the measured f/V (t) ratio.


METHODS
In a cohort prospective study, all consecutive patients who required mechanical ventilation for up to 6 h after elective craniotomy were eligible for inclusion in this study. Patients passing daily screening criteria automatically received a spontaneous breathing trial (SBT). Immediately previous to the extubation, the expired minute volume (VE), breathing frequency (f), and tidal volume (V (t)) were measured and the breathing frequency-to-tidal volume ratio (f/V (t)) was calculated; consciousness level based on Glasgow Coma Scale (GCS) was evaluated at the same time. The extubation was considered a failure when patients needed reintubation within 48 h.


RESULTS
Ninety-two patients were extubated and failure occurred in 16%. Despite 15 patients failed extubation just one of them presented the f/V (t) score over 105. The best cutoff value for f/V (t) observed was 62, but with low specificity (0.53) and negative predictive values (0.29). Area under the ROC curve for the f/V (t) was 0.69 +/- 0.07 (P = 0.02). Patients who failed the extubation process presented higher incidence of pneumonia (80%), higher need for tracheostomy (33%) and mortality rate of 40%.


CONCLUSIONS
The f/V (t) ratio does not predict extubation failure in patients who have undergone elective craniotomy. Patients who fail extubation present higher incidence of pneumonia, tracheostomy and higher mortality rate.
Vidotto
Milena C
MC
Respiratory Physiotherapy Especialization Course, Federal University of São Paulo (Unifesp), Sao Paulo, Brazil. milenavidotto@hotmail.com
Sogame
Luciana C M
LC
Calciolari
Christiane C
CC
Nascimento
Oliver A
OA
Jardim
José R
JR
D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003243:Consciousness; D003244:Consciousness Disorders; D003399:Craniotomy; D003422:Critical Care / Q000379:methods*; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D015656:Respiratory Mechanics; D013990:Tidal Volume; D015300:Ventilator Weaning / Q000379:methods*