Comparative study of two methods of weaning from mechanical ventilation in a cancer surgical intensive care unit

Introduction

The aim of the study was to compare the combination of intermittent mandatory ventilation plus pressure-support ventilation (SIMV+PSV) with intermittent trials of spontaneous breathing (ITSB) using a T-tube as two methods of weaning in a surgical ICU.

Methods

A total of 104 patients who had been ventilated for more than 48 hours in the postoperative period from October 2005 to October 2006 were enrolled in the study. After fulfilling the weaning checklist they were randomly assigned into two groups: SIMV+PSV group (n = 53), and ITSB group (n = 51). In patients assigned to the SIMV+PSV group, the ventilator rate was initially set at 6–8 breaths/minute plus PSV of 15 cmH₂O and then both reduced, if possible, by 2 breaths/minute and 2 cmH₂O each time. Patients able to maintain adequate ventilation with SIMV of 2 breaths/minute and PSV of 5 cmH₂O for at least 2 hours without signs of distress were extubated. Patients assigned to the ITSB group were disconnected from the ventilator and allowed to breathe spontaneously through a T-tube circuit. The duration of the trials was gradually increased. Between the trials, assist–control ventilation was provided for at least 1 hour. Patients able to breathe on their own for at least 2 hours without signs of distress were extubated.

Results

Until the first attempt was made for weaning, all patients received assist–control ventilation because of haemodynamic instability. The following underlying conditions were present: chronic obstructive pulmonary disease in 67 patients, neuromuscular disorders in nine patients, acute lung injury as a result of surgery in 14 patients, asthma in six patients and miscellaneous causes in eight patients. The duration of mechanical ventilation before weaning was 2.5 ± 0.5 days in the SIMV+PSV group vs 2.4 ± 0.4 days in the ITSB group (P = 0.02) and the duration of weaning was 6.2 ± 0.23 hours vs 8.3 ± 0.44 hours in the two groups, respectively (P < 0.01). Patients who remained extubated for 48 hours were classified as having successful extubation – the rate of successful extubation in the first 24 hours of starting weaning was higher for the SIMV group (79.2%) than in the ITSB group (64.7%, P < 0.01). The total duration of mechanical ventilation was 3.3 ± 0.3 days vs 5.2 ± 1.1 days and the ICU length of stay was 5.6 ± 1 days vs 7.5 ± 1.7 days in the two groups, respectively (P < 0.01).

Conclusion

The use of SIMV+PSV as a weaning method in the surgical ICU lead to shorter duration of weaning, a higher rate of successful extubation, a shorter duration of mechanical ventilation and less ICU stay than the use of ITSB.