Automatic versus manual pressure support reduction in the weaning of post-operative patients: a randomized controlled trial

INTRODUCTION: Automatic pressure support reduction based on a target respiratory frequency or MRV is available in the TAEMA-HORUS ventilator for the weaning process in the ICU setting. We hypothesized that MRV is as effective as manual weaning in post-operative ICU patients. METHODS: There were 106 patients selected, in the post-operative period in a prospective, randomized, controlled protocol. When the patients arrived in the ICU after surgery, they were randomly assigned to traditional weaning, consisted of the manual reduction of pressure support every thirty minutes, keeping the RR/TV(L) < 80 till 5-7 cmH20 of PSV. Alternatively, they were assigned to automatic weaning, referring to MRV set with a respiratory frequency target of 15 breaths per minute (the ventilator automatically decreased the PSV level by 1 cmH20 every 4 respiratory cycles, if the patients RR was less than 15 per minute). The primary endpoint of the study was the duration of the weaning process. Secondary endpoints were levels of pressure support, respiratory rate, tidal volume (mL), RR/VT (L), PEEP levels FiO2 and SpO2 required during the weaning process, the need for reintubation and the need for non-invasive ventilation in the 48 hours after extubation. RESULTS: There were no statistically significant differences between the 53 patients selected for each group regarding gender (p=0.541), age (p=0.585) and type of surgery (p=0.172). Nineteen patients were excluded during the trial (4 in the PSV group and 15 in the MRV group, p<0.05). Eighty-seven patients concluded the study, forty-nine patients were weaned manually and thirtyeight automatically. The weaning duration process was 205.41 ± 181.27 minutes (30 to 840 minutes) for the manual group and 157. 33± 129.98 minutes (30 to 545 minutes) for MRV group (p=0.167). PSV levels were significantly higher and RR was lower in MRV compared to that of the PSV manual reduction (p<0.05). Reintubation was not required in either group. NIV was necessary for two patients, in the manual group after cardiac surgery (p=0.505). CONCLUSION: The automatic reduction of pressure support was effective and can be useful for weaning patients in the post-operative period in the ICU, if the patient is receptive to the MRV algorithm