The concept of "baby lung".
BACKGROUND
The "baby lung" concept originated as an offspring of computed tomography examinations which showed in most patients with acute lung injury/acute respiratory distress syndrome that the normally aerated tissue has the dimensions of the lung of a 5- to 6-year-old child (300-500 g aerated tissue).


CONCLUSIONS
The respiratory system compliance is linearly related to the "baby lung" dimensions, suggesting that the acute respiratory distress syndrome lung is not "stiff" but instead small, with nearly normal intrinsic elasticity. Initially we taught that the "baby lung" is a distinct anatomical structure, in the nondependent lung regions. However, the density redistribution in prone position shows that the "baby lung" is a functional and not an anatomical concept. This provides a rational for "gentle lung treatment" and a background to explain concepts such as baro- and volutrauma.


CONCLUSIONS
From a physiological perspective the "baby lung" helps to understand ventilator-induced lung injury. In this context, what appears dangerous is not the V(T)/kg ratio but instead the V(T)/"baby lung" ratio. The practical message is straightforward: the smaller the "baby lung," the greater is the potential for unsafe mechanical ventilation.
Gattinoni
Luciano
L
Istituto di Anestesia e Rianimazione, Fondazione IRCCS, Ospedale Maggiore Policlinico, Mangiagalli, Regina Elena di Milano, Università degli Studi, Milan, Italy. gattinon@policlinico.mi.it
Pesenti
Antonio
A
D015199:Extracorporeal Membrane Oxygenation; D006801:Humans; D008954:Models, Biological; D011175:Positive-Pressure Respiration / Q000009:adverse effects* / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy*; D014057:Tomography, X-Ray Computed