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A randomized control trial comparing adaptive support ventilation with pressure-regulated volume control ventilation in weaning patients after cardiac surgery


Adaptive support ventilation (ASV) is a minute ventilation-controlled mode governed by a closed-loop algorithm. The combination of target tidal volume and respiratory rate is continuously adjusted with the goal of maintaining the patient in isominute ventilation, and thus reducing the work of breathing. A recent study demonstrated a reduction in time to extubation in patients ventilated in the ASV mode compared with those ventilated in synchronized intermittent mandatory ventilation (SIMV) followed by a pressure support mode [1]. This might be explained by a delay in switching the patient from SIMV to the pressure support mode. Pressure-regulated volume control (PRVC) with automode is a better comparator as it delivers pressure control breaths in the absence of triggering and automatically switches to pressure support breaths when triggered. We compared ASV with PRVC in the duration of intensive care ventilation in 50 patients after elective coronary artery bypass surgery.


Patients were randomized to either ASV or PRVC on arrival in the ICU. Respiratory weaning progressed through three phases: phase 1 (start of intensive care ventilation to recovery of sustained spontaneous breaths), phase 2 (end of phase 1 to peak airway pressures <15 cmH2O during spontaneous breaths), phase 3 (T-piece trial). Following a successful T-piece trial, patients were extubated. The primary outcome was the duration of intensive care ventilation. Secondary outcomes were the time from intensive care admission to extubation, duration of phases 1–3, number of patients failing to wean, arterial blood-gas samples and ventilator setting changes made prior to extubation.


Forty-eight patients completed the study. The duration of intensive care ventilation was significantly shorter in the ASV than the PRVC group (165 (120–195) vs 480 (360–510) min; P < 0.001). The observed reduction in intubation time was mainly a result of shortening of phase 1 (21 (6–41) min in the ASV group vs 60 (24–153) min in the PRVC group) and of phase 2 (147 (91–171) min in the ASV group vs 357 (163–458) min in the PRVC group) (P < 0.001). Seventeen patients in the PRVC and three patients in the ASV group did not reach the protocol criteria for a T-piece trial within 8 hours but were successfully extubated. There were no significant differences in the number of arterial blood-gas samples taken or ventilator setting changes between the groups.


ASV is associated with earlier extubation, without an increase in clinician intervention, when compared with PRVC in patients undergoing uncomplicated cardiac surgery.


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Gruber, P., Gomersall, C., Leung, P. et al. A randomized control trial comparing adaptive support ventilation with pressure-regulated volume control ventilation in weaning patients after cardiac surgery. Crit Care 12, P326 (2008).

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  • Volume Control Ventilation
  • Adaptive Support Ventilation
  • Elective Coronary Artery Bypass
  • Synchronize Intermittent Mandatory Ventilation
  • Spontaneous Breath