The recent article by Thille et al.  1and the accompanying editorial by Rouby2discuss the effects of positive end-expiratory pressure (PEEP) on pulmonary recruitability in patients with adult respiratory distress syndrome (ARDS). Thille et al.  found that alveolar recruitment was similar in pulmonary and extrapulmonary ARDS and concluded that PEEP levels should not be determined based on cause of ARDS.1However, the type of ARDS could not be classified in 37% of the patients in their retrospective study,1an important point that is further discussed in Rouby’s editorial.2In the study by Thille et al. , the response to PEEP was assessed by pressure-volume curves only, and the effect of PEEP on oxygenation is not reported.

More than 30 yr ago, we described the variable effect of PEEP on oxygenation in patients with ARDS.3,4We found that both the short-term and the long-term effects of PEEP on oxygenation response in patients with sepsis were statistically smaller compared with that in patients without sepsis, and we concluded that ARDS associated with sepsis seems to be the result of a more severe pulmonary insult.3In a subgroup of trauma patients, we found again that the improvement in oxygenation after the application of PEEP in patients who developed sepsis was significantly smaller than that of patients without sepsis and without lung contusion.4 

As imperfect as they are by today’s standards, these two very old studies do have relevance to the ongoing discussion about the effectiveness of pulmonary recruitment in ARDS because, in contrast to Thille et al. ’s findings, they support the view that the effectiveness of PEEP does depend on the etiology of ARDS. It is unfortunate that for too many years we have not made much progress in better defining the various subgroups of ARDS. The clinician at the bedside is still left with one option only, namely, apply PEEP and assess its consequences. In fact, the response to PEEP may help in making the diagnosis.

Sheba Medical Center, Tel Aviv University, Tel Hashomer, Israel.

Thille AW, Richard J-C, Maggiore SM, Ranieri VM, Brochard L: Alveolar recruitment in pulmonary and extrapulmonary acute respiratory distress syndrome: Comparison using pressure-volume curve or static compliance. Anesthesiology 2007; 106:212–7
Rouby JJ: Recruitment in pulmonary and extrapulmonary acute respiratory distress syndrome: The end of am? Anesthesiology 2007; 106:203–4
Cotev S, Perel A, Katzenelson R, Eimerl D: The effect of PEEP on oxygenating capacity in acute respiratory failure with sepsis. Crit Care Med 1976; 4:186–92
Perel A, Olshwang D, Eimerl D, Katzenelson R, Cotev S: The variable effect of PEEP in acute respiratory failure associated with multiple trauma. J Trauma 1978; 18:218–21