Consequently, ABT-199 concentration patients have varying degrees of hypoxemia refractory to oxygen administration. This review presents the evolution of definitions of ARDS and their future implications for clinical and experimental research. A definition is a “clear determination of the limits of anything, especially a disease process”.6 In general, definitions circumscribe a condition, providing limits between what is and what is not its essential nature.7 It so happens that sometimes diseases,

and especially syndromes, have imprecise limits, making the diagnosis difficult, as occurs with ARDS. Considering that, despite recent advances in the monitoring and treatment of critically-ill patients with ARDS, mortality remains high for the syndrome,5 especially in more severe cases, it is important to continually improve diagnostic criteria in order to reach a definition that has greater applicability in the clinical setting. Additionally, the review of the disease definition is important for research, for clinicians in daily practice, and for administrators. As for research, GDC-941 it is useful to obtain new information about the pathogenesis of ARDS, seeking connection between basic science and the clinical setting, as therapeutic modalities can be constantly tested

in the basic research environment and sometimes transported into daily practice. Moreover, a more precise definition would allow the comparison PLEKHM2 of findings from several clinical studies with higher degree of certainty.8 Regarding the actual clinical

practice, a precise definition would allow for earlier institution of established and tested therapeutic methods, such as the use of lung-protective ventilation with limited tidal volume and pressure plateau.9 and 10 Additionally, the assessment of individual prognosis would be improved, facilitating the relationship with patients’ relatives and enhancing information given to them. In the field of hospital administration, it is understood that epidemiological studies on ARDS are crucial to provide data on its incidence and frequency, which are useful elements for administrators to allocate the limited resources of the health system for the treatment of these patients. Obviously, these studies are based on a specific definition of the disease,11 and many researchers have raised the possibility that the reported differences regarding the mortality rate of ARDS are primarily due to the variability in its definition.12 Ever since the description of the disease was published by Ashbaugh et al.3 in 1967, several non-standard definitions were used in clinical studies. In 1976, Bone et al.13, when describing the association between DIC and ARDS, used as diagnostic criteria of the syndrome the presence of arterial partial pressure of oxygen (PaO2) ≤ 70 mmHg with a fraction of inspired oxygen (FiO2) ≥ 0.5 and of positive-end expiratory pressure (PEEP), whose value was not specified. In 1982, Pepe et al.