Figure 9.

Decision tree of the BLUE protocol. This decision tree, which has been made as simple as possible, may appear complex to some. In actual fact, it simplifies the huge body of knowledge that any physician dealing with respiratory failure should master (anatomy, physiology, pathophysiology, clinical signs, imaging and biological or other paraclinical signs). It is not designed to provide 100% of diagnoses of acute dyspnoea; it has been simplified with a target overall accuracy just over 90% (90.5%). Reproduced and modified from [7] with permission from the publisher.