The oxygen cost of breathing may predict weaning from mechanical ventilation better than the respiratory rate to tidal volume ratio
S. A. Shikora, P. N. Benotti and J. A. Johannigman
Department of Surgery, Wilford Hall USAF Medical Center, Lackland AFB, Texas.
OBJECTIVE: To compare the respiratory rate to tidal volume ratio with the
oxygen cost of breathing to see which could more accurately predict the
outcome of ventilator weaning for surgical patients. DESIGN: Prospective
comparison of two modalities used to predict the likelihood of successful
ventilator weaning. PATIENTS: Twenty-eight consecutive patients with
chronic respiratory insufficiency requiring long-term mechanical
ventilation in the surgical intensive care unit at New England Deaconess
Hospital, Boston, Mass, were studied. MAIN OUTCOME MEASURES: The oxygen
cost of breathing and the respiratory rate to tidal volume ratio were
measured during spontaneous breathing. Patients extubated within 2 weeks of
being studied were designated as extubated while patients not extubated
within this period or requiring reintubation were recorded as not
extubated. RESULTS: The oxygen cost of breathing predicted successful
extubation in all five patients who were extubated, and failure in 20 of 23
patients who could not be extubated (sensitivity, 100%; specificity, 87%).
In contrast, the respiratory rate to tidal volume ratio predicted
extubation for only two of five patients who were extubated and predicted
failure in only 12 of 23 patients who could not be extubated (sensitivity,
40%; specificity, 52%). CONCLUSION: For this group of patients requiring
prolonged ventilation, the oxygen cost of breathing proved to be a more
reliable predictor of both successful extubation and failure.
