© 2003 American Thoracic Society
Recruitment maneuvers during lung protective ventilation in acute respiratory distress syndromeTo the Editor:In a recent report, Villagrá and colleagues (1) examined the efficacy of recruitment maneuvers in a group of acute respiratory distress syndrome (ARDS) patients during protective ventilation. When reading this paper I was concerned by the original conception of "protective ventilation" advocated by these authors. It is usually admitted that protective ventilation is a strategy that limits airway pressure to avoid alveolar overdistension. A recent example of this strategy can be found in a large cooperative study (2), where patients subjected to a protective approach had a limited airway pressure (plateau pressure: 25 ± 7 cm H2O at Day 1, 26 ± 7 at Day 2, 26 ± 7 at Day 3). In the same study, a second group of patients was subjected to a traditional approach without airway pressure limitation (plateau pressure: 33 ± 9 cm H2O at Day 1, 34 ± 9 at Day 2, 37 ± 9 at Day 3), to compare mortality. With a plateau pressure of 32 ± 5 cm H2O, and a mean airway pressure of 20 cm H2O, airway pressures in patients with ARDS treated by Villagra and colleagues are closer to this second group (1), and one may wonder what exactly is protective in Villagrá and colleagues' strategy. Unfortunately, these authors did not give the mortality of their patients, which could be a strong argument demonstrating "protection," in a group where predicted mortality can be calculated as 26% (APACHE II: 17 ± 7) (1).
University Hospital Ambroise Paré Boulogne Cedex, France REFERENCES
From the Authors:We thank Dr. Jardin for his comments and interest regarding our study (1). Protective lung ventilation in patients with ARDS is a strategy devoted to minimizing both overdistention and cyclic collapse and reopening of alveolar regions. Consequently, we designed our protocol according to the method proposed by Amato and colleagues (2). Lung protection requires appropriate inspiratory driving pressure (< 20 cm H2O) to reduce inspiratory stretching and moderate/high levels of positive end-expiratory pressure (PEEP) to avoid end-expiratory alveolar collapse. These two variables were independently associated with better survival (2). In our study (1), PEEP was set at 3 cm H2O above the lowest inflection point (LIP) observed in the inspiratory part of the respiratory system pressure–volume curve. Therefore, our ventilatory approach using low tidal volume (7.2 ± 1.2 ml/kg), low driving pressure (18.5 cm H2O), high PEEP (14 ± 1.3 cm H2O), and a mean plateau pressure in the upper recommended limit (32 cm H2O) should be considered a protective ventilatory strategy rather than a deleterious one. The ARDS Network study (3) also proved the beneficial effect on survival of low tidal volume (6 ml/kg) compared with high tidal volume (12 ml/kg). Since the design and objectives of the ARDS Network study and ours were different, it is difficult to draw clinical conclusions based on differences between ventilatory strategies.Mortality in our series of ARDS patients was 65% (1). Mortality rates in ARDS range from 31 to 71% in different studies (2–4). Significant differences in mortality rates among studies may be attributed to differences in type and strength of study designs, and to the wide variety of definitions used for this syndrome (4). Therefore, it is only possible to calculate predicted mortality using the APACHE II score if the number of patients is large and a variety of etiologies and underlying diseases is included in the analysis. Since a small number of ARDS patients were included in our physiologic study (1), it would be statistically inappropriate to predict mortality from the APACHE II score at admission (5).
Hospital de Sabadell, Corporació Parc Taulí Sabadell, Spain REFERENCES
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