Ultrasound in the critically ill: Look for lung water!

The use of ultrasound in the intensive care unit (ICU) is growing rapidly because of the problem of radiation hazard, the transportation of critically ill patients, and so on. Most of all, the most prominent area of ICU ultrasound is the lung ultrasound (LUS), with which it is really possible to look at the air inside the lung, previously considered only a kind of obstacle in the evaluation with ultrasound, from another perspective.[1] That is, in the normal lungs, the reverberation artifact caused by the air was referred to as “A-line,” and we are able to define the ultrasonically normal lung with the finding of the “lung sliding.” On the other hand, in pathologic lungs, excluding pneumothorax, and pleural effusion, lungs are filled by water or fluid, not air and able to be distinguished in terms of severity as “air-fluid ratio.” Therefore, the situation that alveolus is still aerated, but interstitium is filled with water is called ultrasonically the “interstitial syndrome” which can be quantified in degree in terms of the “B lines”.[2]