Effect of Respiratory Muscle Performance on Ventilatory Weaning

Background: In order to determine whether the use of pressure-support ventilation (PSV) could retrain the respiratory muscles and enhance the success rate after patients had failed a spontaneous breathing trial (SBT), we developed sequential weaning protocols and monitored the changes in respiratory muscle performance during the weaning process. Methods: A total of 103 patients requiring mechanical ventilation and admitted to a tertiary hospital were enrolled. Weaning was first attempted with a once-daily spontaneous breathing trial (OSBT). For patients who failed this trial, PSV was used until a pressure of 12 cmH2O was reached, followed by SBT. Results: Sixty-six (64%) patients were successfully weaned with the OSBT. Twenty-three (62%) of the remaining 37 patients managed with PSV were successfully weaned, yielding an 86% (89/103) success rate for those who were weaned within 78±37 hours. Compared with those who failed the OSBT, the patients who succeeded with the OSBT had a significantly higher maximal inspiratory pressure (Pimax), higher percentage of change in Plmax (△Plmax%), and lower frequency-to-tidal volume ratio (f/VT). Those who succeeded with PSV also had a significantly higher △Plmax% than those who failed. Conclusions: Initial respiratory muscle performance is predictive of early successful weaning by OSBT, but not later weaning by PSV. PSV was able to help wean those patients who failed OSBT, with a success rate comparable to that of early weaning by OSBT. PSV might not produce significant augmentation of respiratory muscle strength, but was able to delay the decrease of respiratory muscle strength in the weaning process.