© 2003 American Thoracic Society
Weaning and Noninvasive VentilationThe Odd CouplePulmonary Rehabilitation and Respiratory Intensive Care Unit Fondazione S. Maugeri Pavia, Italy Mechanical ventilation delivered through an endotracheal tube is a life-saving intervention, which is instituted essentially to buy time and to allow recovery from the underlying disorder causing the respiratory failure. Because it is supportive, rather than curative, and may be associated with unwanted side effects and life-threatening complications (1), mechanical ventilation should be discontinued as soon as possible. Systematic daily testing of the patient's capability to tolerate a period of spontaneous breathing using relatively undemanding functional predictors, as opposed to the subjective clinical judgment, significantly reduces the time spent on mechanical ventilation and the reintubation rate (2). Nevertheless, a considerable number of patients repeatedly fail the spontaneous breathing trials and suffer difficult weaning. Prolonged endotracheal intubation increases the risk of nosocomial pneumonia (3), which further complicates weaning, and leads to a vicious circle. Noninvasive ventilation is effective in avoiding the need for endotracheal intubation and improving clinical outcome of patients with acute hypercapnic respiratory failure caused by an exacerbation of chronic obstructive pulmonary disease (4, 5). Noninvasive ventilation has been proposed for several other applications, including facilitation of weaning and extubation. One major determinant of weaning failure is an excessive load on the respiratory muscles after disconnection from the ventilator (6). In patients who fail a T-piece trial, invasive and noninvasive ventilation are equally effective in reducing inspiratory effort and improving gas exchange, although noninvasive ventilation results in better patient comfort (7). By allowing effective ventilator assistance, while eliminating the risks associated with endotracheal intubation, noninvasive ventilation may break the vicious circle and be a valuable alternative to the conventional weaning techniques. Although attractive, the idea of extubating a patient who has just failed a trial of spontaneous breathing may appear odd and may be difficult to accept. Two randomized trials, subsequent to a few observational studies, have recently been performed to test whether or not early extubation followed by immediate noninvasive ventilation may be an effective and safe alternative to standard weaning techniques in stable patients who fail the first T-piece trial (8, 9). Both studies find that this new approach is successful in maintaining adequate gas exchange and, compared with a conventional weaning technique, the new approach shortens the duration of invasive mechanical ventilation. In one of the two studies, noninvasive ventilation also reduces the time spent in the intensive care unit, avoids nosocomial pneumonia, and improves survival (8). A third randomized trial assessing the efficacy of noninvasive ventilation in facilitating the weaning process is presented in this issue of the AJRCCM (pp. 70–76) (10). Based on a solid and compelling design, this investigation confirms all the positive findings of the two previous investigations and, in addition, shows a reduction in overall hospital stay and need for tracheotomy. In addition to confirming previous results, the new study has a few peculiar features. First, the patients enrolled had, for three consecutive days, failed a T-tube trial, and therefore were more likely candidates for prolonged weaning. In fact, the average duration of mechanical ventilation in the control group, who underwent conventional weaning, was 20.1 days, as opposed to 16.7 (8) and 11.1 (9) days in the two previous studies. Only 14% of the patients who received noninvasive ventilation required intubation, as opposed to 27% of the patients receiving conventional weaning, showing that in expert hands this technique is not only effective, but also relatively safe. Indeed, this rate of failure does not exceed that encountered when noninvasive ventilation is administered to prevent endotracheal intubation during an episode of acute hypercapnic respiratory failure (5, 6). It is, however, important to remark that noninvasive ventilation has specific contraindications which considerably restrict its use, as indicated by the fact that 30% of all the eligible patients in this study met the exclusion criteria. Second, different from the two previous trials, which only included patients with chronic obstructive pulmonary disease (8) or other chronic respiratory disorders (9), Ferrer and coworkers (10) recruited every stable patient who had failed a spontaneous breathing trial through an orotracheal tube for three consecutive days, regardless of the underlying disease. Despite this lack of selectivity, however, almost 80% of the patients were affected by chronic pulmonary disorders. Although the prevalence of disease states may vary among units, this finding is consistent with the view that patients who experience difficult weaning are most likely to have a chronic respiratory disorder (11) and especially chronic obstructive pulmonary disease (12), a statement somewhat challenged by the results of a large prospective multicenter cohort study recently published (1). It remains to be determined whether or not the benefits of noninvasive ventilation for weaning can be extended to other patient groups. Undoubtedly, the study by Ferrer and coworkers (10) adds considerable evidence in favor of the use of noninvasive ventilation to facilitate weaning. Considering that difficult-to-wean patients have higher morbidity and mortality and consume a substantial amount of health care resources, these results could lead many of those who have so far considered noninvasive ventilation ineffective or unsafe to change their mind and reevaluate its potential. Although a relatively straightforward technique, noninvasive ventilation has several specific features that must be taken into account to avoid negative and disappointing results (13). As the use for weaning purposes is one of the most challenging and demanding applications for noninvasive ventilation, and requires a skilled and well trained staff, it is definitely not advisable to start with this specific application for implementing the technique in a unit. There is not a unique reason why weaning failure occurs, and many factors not strictly related to the ventilator management may contribute to it (14). Noninvasive ventilation is not the ultimate solution to the problem of weaning, but may be valuable for certain patients without contraindication and predominantly for those with chronic respiratory disease. It is just another brick in the wall. REFERENCES
This article has been cited by other articles:
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
