Introduction:

weaning from invasive mechanical ventilation (IMV) is an essential element in the treatment of the critical patient. Despite this, the incidence of IMV weaning failure is not negligible, even with good predictors of success. The ventilatory ratio (VR) has been described as a bedside tool to evaluate the patient’s ventilatory deterioration. Its value reflects the capacity of the lungs to eliminate carbon dioxide (CO2). In several studies, a high VR has been described as an independent predictor of mortality in patients with acute respiratory distress syndrome (ARDS); however, there are no studies that support its use as a tool to determine the probability of IMV weaning failure.

Objective:

to evaluate the use of VR to predict IMV weaning failure in critically ill patients.

Material and methods:

retrospective cohort, in patients in the intensive care unit (ICU) of the ABC Medical Center from January 2021 to August 2023. Patients with IMV in a ventilatory weaning protocol were evaluated. The VR was calculated with the formula VR = measured VE × measured PaCO2 / predicted VE x ideal PaCO2. A ROC curve and area under the curve analysis were performed to determine the best predictive performance of VR for IMV weaning failure. The cut-off points of 1, 1.2, 1.4, 1.6 were established and sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for each one. Likewise, the regression coefficient was estimated for each cut-off point through logistic regression models. For all determinations, the 95% confidence interval was estimated and a p value < 0.05 was considered statistically significant.

Results:

the cut-off point with the best performance to predict extubation failure was a VR > 1.4 with sensitivity 82.6%, specificity 56.4%, PPV 52.8% and NPV 84.6%. Likewise, the VR was positively involved in the mortality of patients in the ICU. In this regard, the best cut-off point was VR > 1.6 with sensitivity 72.7%, specificity 76.5%, PPV 40.0% and NPV 92.9%.

Conclusions:

VR > 1.4 is a new tool to predict failure to withdraw from IMV.

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