© 2007 American Thoracic Society
Computer-driven Protocolized Weaning from Mechanical VentilationTo the Editor:We read with interest the recent article by Lellouche and colleagues in which they show that a computer-driven weaning protocol, as compared with human-controlled weaning guidelines, significantly reduces duration of mechanical ventilation and length of stay in the intensive care unit (1). The authors deserve compliments for their efforts. Although it has been shown to be difficult to test the efficiency of protocols in randomized controlled trials (2), the investigators were very successful in this respect. We agree with them that a computer-driven weaning protocol will become the future of weaning. Indeed, adherence to weaning protocols can be disappointingly low, even if caregivers are well trained (3). Despite the clear presentation of results, some questions remain. The so-called "comfort zone," as clearly defined in the computer-driven weaning protocol, may differ strongly from what was accepted as "comfortable" in the human-controlled weaning guidelines. In the computer-driven weaning arm, "comfort" was defined as having a respiratory rate between 15 and 30 breaths/min, a tidal volume above a minimum threshold (> 300 ml, > 250 ml if weight < 55 kg), and an end-tidal CO2 below a maximal threshold. Only when these criteria were met was the support adapted to a lower level until minimal levels were reached. In the control arm, "comfort" was only minimally defined. In fact, the attending physician had to decide whether the patient was "comfortable enough" to adapt support to lower levels. Of course, this difference is in fact part of what is being compared, but we hypothesize that this part may be larger than expected. For instance, even with a respiratory rate between 15 and 30 breaths/min, the physician may have decided not to lower the support level in case the breathing pattern gave the impression that the patient was "uncomfortable." In addition, no data are given on tidal volumes used in this study during the weaning process. Indeed, no target tidal volumes were given in the human-controlled weaning guidelines, while with computer-driven weaning only the minimal threshold of tidal volumes was set. Lung-protective mechanical ventilation using lower tidal volumes has been found to benefit patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS) (4). Of note, it is advisable to use lower tidal volumes throughout the period of mechanical ventilation, that is, also during weaning. Although we are not informed about the incidence of ALI/ARDS in the study by Lellouche and coworkers, we assume a majority of their patients must have suffered from ALI/ARDS. From experience, we know physicians are reluctant to use lower tidal volumes (5), in particular because their use may result in higher respiratory rates. Given these questions, can the authors provide us with data on tidal volumes and respiratory rates in the two arms of the study?
Academic Medical Center, Amsterdam, The Netherlands FOOTNOTES
Conflict of Interest Statement: L.M.K. has no financial relationship with a commercial entity that has an interest in the subject of this manuscript. M.J.S. has participated as a speaker in scientific meetings or courses organized and financed by various pharmaceutical companies (Maquet, Hamilton, Eli Lilly); he received REFERENCES
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1,000 in 2006 for speaking at conferences sponsored by Maquet; he received $12,500 in 2005 and 2006 from Hamilton as research grants for performing a mono-center clinical trial; another Hamilton-sponsored grant is pending.