Physiology versus evidence based guidance for critical care practice

Overview: The way of ventilating the ARDS lung deeply changed over the last 30 years, primarily due to a better understanding of physiological mechanisms involved in the mechanical ventilation, as heart and lung interaction and generation of ventilator induced lung injury. All this led to a "gentle lung ventilation" which, although proposed years before, became evident only after a large randomized trial. Understanding mechanisms is the basis of the medical reasoning. The lack of application of physiological sound approaches just "because evidence is lacking" may be of disadvantage for a single patient. We lost, as an example, 30 years of potential benefit of prone position, evident from a physiological perspective, just because "clinical evidence" was not available. Take home message Evidence is the final step of a long journey. Lack of evidence of promising and physiologically sound approach should not discourage the application in the single patient.