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Randomized Controlled Trial
. 2009;13(1):R6.
doi: 10.1186/cc7695. Epub 2009 Jan 26.

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

Corinne Taniguchi  1 , Raquel C Eid, Cilene Saghabi, Rogério Souza, Eliezer Silva, Elias Knobel, Angela T Paes, Carmen S Barbas
Affiliations
Randomized Controlled Trial

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

Corinne Taniguchi et al. Crit Care. 2009.

Abstract

Introduction: Reduction of automatic pressure support based on a target respiratory frequency or mandatory rate ventilation (MRV) is available in the Taema-Horus ventilator for the weaning process in the intensive care unit (ICU) setting. We hypothesised 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, randomised, controlled protocol. When the patients arrived at the ICU after surgery, they were randomly assigned to either: traditional weaning, consisting of the manual reduction of pressure support every 30 minutes, keeping the respiratory rate/tidal volume (RR/TV) below 80 L until 5 to 7 cmH2O of pressure support ventilation (PSV); or 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 cmH2O every four respiratory cycles, if the patient's 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, RR, TV (mL), RR/TV, positive end expiratory pressure 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: In the intention to treat analysis 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 presented complications during the trial (4 in the PSV manual group and 15 in the MRV automatic group, p < 0.05). Nine patients in the automatic group did not adapt to the MRV mode. The mean +/- sd (standard deviation) duration of the weaning process was 221 +/- 192 for the manual group, and 271 +/- 369 minutes for the automatic group (p = 0.375). PSV levels were significantly higher in MRV compared with that of the PSV manual reduction (p < 0.05). Reintubation was not required in either group. Non-invasive ventilation was necessary for two patients, in the manual group after cardiac surgery (p = 0.51).

Conclusions: The duration of the automatic reduction of pressure support was similar to the manual one in the post-operative period in the ICU, but presented more complications, especially no adaptation to the MRV algorithm.

Trial registration number: ISRCTN37456640.

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Figures

Figure 1
Figure 1
Study design. FiO2 = fraction of inspired oxygen; MRV = mandatory rate ventilation; PEEP = positive end-expiratory pressure; PCV = pressure controlled ventilation; PSV = pressure support ventilation; RR = respiratory rate; SpO2 = arterial oxygen saturation; TV = tidal volume.
Figure 2
Figure 2
Boxplot of the median duration of weaning in manual and automatic weaning modes.
Figure 3
Figure 3
Pressure support ventilation (PSV) level variation throughout weaning. Each PSV refers to increments of 30 minutes in the weaning process. There was a significant difference between the automatic mode and the manual mode of weaning (p < 0. 01). The numbers at the bottom of the figure refer to the number of patients that stayed in the weaning trials through time.
Figure 4
Figure 4
Variation of tidal volume throughout weaning. Each tidal volume value refers to increments of 30 minutes in the weaning process. There was no significant difference between the automatic mode and the manual mode (p = 0.31). The numbers at the bottom of the figure refer to the number of patients that stayed in the weaning trials through time.
Figure 5
Figure 5
Variation of respiratory rate throughout weaning. Each respiratory rate value refers to increments of 30 minutes in the weaning process. There was no difference between the automatic mode and the manual mode (p = 0.86). The numbers at the bottom of the figure refer to the number of patients that stayed in the weaning trials through time. bpm = breaths per minute
Figure 6
Figure 6
Variation in fraction of inspired oxygen (FiO2) throughout weaning. Each FiO2 value refers to increments of 30 minutes in the weaning process. There was no significant difference between the automatic mode and the manual mode (p = 0.37). The numbers at the bottom of the figure refer to the number of patients that stayed in the weaning trials through time. Decrement of FiO2 in both groups along time (p = 0.028)
Figure 7
Figure 7
Variation of respiratory rate (RR)/tidal volume (TV) throughout weaning. Each RR/TV refers to increments of 30 minutes in the weaning process. There was no significant difference between the automatic mode and the manual mode (p = 0.78). The numbers at the bottom of the figure refer to the number of patients that stayed in the weaning trials through time.
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