There are several pieces of evidence showing occurrence of pulmonary edema (PE) 
in healthy subjects in extreme conditions consisting of extreme psychophysical 
demand in normal environment and psychophysical performances in extreme 
environment. A combination of different mechanisms, such as mechanical, 
hemodynamic, biochemical, and hypoxemic ones, may underlie PE leading to an 
increase in lung vascular hydrostatic pressure and lung vascular permeability 
and/or a downregulation of the alveolar fluid reabsorption pathways. PE can be 
functionally detected by closing volume measurement and lung diffusing capacity 
test to different gases or directly visualized by multiple imaging techniques. 
Among them chest ultrasonography can detect and quantify the extravascular lung 
water, creating "comet-tail" ultrasound artefacts (ULCs) from water-thickened 
pulmonary interlobular septa. In this paper the physiopathological mechanisms of 
PE, the functional and imaging techniques applied to detect and quantify the 
phenomenon, and three models of extreme conditions, that is, ironman athletes, 
climbers and breath-hold divers, are described.