Ventilator Weaning: RT-Driven or R2D2-Driven?
Abstract & Commentary
By Saadia R. Akhtar, MD, MSc, Idaho Pulmonary Associates, Boise, is Associate Editor for Critical Care Alert.
Idaho Pulmonary Associates, Boise
Dr. Akhtar does research for Eli Lilly.
Synopsis: This multicenter, randomized trial demonstrated that a computerized protocol, when compared with usual physician-driven weaning, reduced duration of mechanical ventilation and ICU length of stay.
Source: Lellouche F, et al. A multicenter randomized trial of computer-driven protocolized weaning from mechanical ventilation. Am J Respir Crit Care Med. 2006;174:894-900.
A previously described "closed-loop knowledge based system" placed into a standard ventilator may be used to guide weaning via the pressure support mode. The system uses continuously recorded patient data on respiratory rate, tidal volume and end-tidal CO2 to adjust the pressure support (PS) level. Once a specified minimum level of PS is reached, a spontaneous breathing trial is completed and the computer makes a recommendation for or against extubation. Noting that there are excellent data supporting protocol-driven ventilator weaning,1 but that protocols may be difficult to implement, the authors hypothesized that a computerized approach may be superior to usual care.
The study was conducted in 5 European medical-surgical ICUs. Patients were mechanically ventilated for ≥ 24 hours on ≤ 50% oxygen with a variety of criteria including positive end-expiratory pressure ≤ 8 cm H2O, hemodynamic stability and minimal sedation. Exclusion criteria included poor neurological or overall prognosis, presence of a do-not-resuscitate order or a tracheostomy. At study entry, patients were placed on PS 15 cm H2O for 30 minutes. Once tolerated, they were randomized to computer-driven (CDW) or usual weaning. The primary end points were time to successful extubation (defined as 72 hours without ventilator support) and duration of mechanical ventilation. An estimated sample size of 75 per group was necessary to detect reduction in weaning time of 2 days with power 0.8 and P ≤ 0.05. Usual statistical methods were employed.
Over 10 months, 1014 mechanically ventilated patients were screened, 147 met study criteria and 144 were randomized (74 CDW, 70 controls). Patients in the 2 groups were similar with respect to demographics, severity of illness, organ dysfunction, comorbidities and duration of mechanical ventilation prior to study entry (about 4 days). Weaning time was decreased from median 5 days in the control group to 3 days in the CDW group. (There was a median delay of 1 day between the CDW system recommending extubation and physicians proceeding with this.) Total duration of ventilation was 7.5 days vs 12 days; and ICU length of stay was 12 days vs 15.5 days.
There were no significant differences between the groups in extubation failure, hospital length of stay, mortality, or ventilator-associated pneumonia. Need for non-invasive ventilation after extubation was significantly less in the CDW group. There was no significant difference in sedation or paralytic use between the groups or in the period before entry into the study vs afterwards. Finally, 10 patients were removed from the CDW system due to clinical worsening.
Commentary
There is good evidence that weaning time or time on mechanical ventilation can be safely reduced by use of weaning protocols driven by nurses or respiratory therapists.1-3 Data also suggest that standardized practice in closed units with formal rounds and adequate levels of intensivist staffing may yield outcomes similar to those seen with specific protocols.4
CDW is an interesting and novel alternative approach to liberation from mechanical ventilation. There are reasons to hypothesize that CDW may be superior to protocols (or standardized and consistent practice patterns) that rely on human beings. It ensures more complete compliance: there are considerable data in the literature on the difficulty of achieving compliance with 'human-driven' protocols.5,6 CDW may be faster than a human-driven approach in that it operates and weans PS continuously for 24 hours a day (as compared to intermittent assessment for reduction of PS or just a once a day spontaneous breathing trial). (Even CDW has its limitations: in this study when patients met extubation criteria per CDW recommendations, humans added on average a perhaps-unnecessary day to the time on mechanical ventilation.)
Lellouche et al's work does address their primary hypothesis, demonstrating that CDW is superior to their 'usual care.' The study however does not answer the question of whether CDW is superior to the currently recommended standardized protocol-driven weaning methods. The centers in question relied on physician direction for weaning. Although we are told that many had formal protocols or structured practices in place for weaning, there is no information available on the means/degree of implementation.
This study does demonstrate that CDW may be incorporated relatively easily and provides motivation for future comparisons with more clearly established "protocolized" weaning methods. I await such further studies and suspect that CDW may ultimately be found to be the best choice for some units: even if shown to be equal rather than superior to current best care, CDW may work well for intensive care units without an adequate number of support staff trained in the use of weaning protocols and/or those units with limited numbers of physicians trained in critical care.
References
- Ely EW, et al. Mechanical ventilator weaning protocols driven by non-physician health-care professionals: evidence-based practice guidelines. Chest. 2001;120:454S-463S.
- Ely EW, et al. Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously. N Engl J Med. 1996;335:1864-1869.
- Marelich GP, et al. Protocol weaning of mechanical ventilation in medical and surgical patients by respiratory care practitioners and nurses: effect on weaning time and incidence of ventilator-associated pneumonia. Chest. 2000;118:459-467.
- Krishnan JA, et al. A prospective, controlled trial of a protocol-based strategy to discontinue mechanical ventilation. Am J Respir Crit Care Med. 2004;169:673-678.
- Ely EW, et al. Large scale implementation of a respiratory therapist-driven protocol for ventilator weaning. Am J Respir Crit Care Med. 1999;159:439-446.
- Rubenfeld GD. Implementing effective ventilator practice at the bedside. Curr Opin Crit Care. 2004;10:33-39.
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