The concept of liquid breathing by land animals is extremely counterintuitive and virtually oxymoronic. The notion of liquid breathing became possible in the 1940s, however, with the development of a new class of synthetic compounds, the perfluorocarbon liquids. Relatively soon after the development of the perfluorocarbon liquids, it was realized that they possessed a range of physical properties almost ideally suited for liquid breathing.

The “proof of concept” was established in 1996 by Clark and Gollan,<sup>7Clark L.C., Gollan F. Survival of mammals breathing organic liquids equilibrated with oxygen at atmospheric pressure Science 1966 ;  152 : 1755-1756

Cliquez ici pour aller à la section Références</sup> who demonstrated that mice could survive while submerged in an oxygenated perfluorocarbon. Furthermore, after the animals were removed from the liquid, a smooth transition to air breathing occurred as the perfluorocarbon liquid (which possesses a high vapor pressure at body temperature) evaporated from their lungs. Finally, the mice survived long term, without apparent adverse effects. This landmark study stimulated subsequent research into the physiology of perfluorocarbon liquid breathing in normal animals and, subsequently, the potential salutary effect of liquid breathing in animals or humans with lung injury.

Furthermore, the optimum approach to traditional gas mechanical ventilation in patients with acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) remains uncertain and controversial. Particularly over the past decade, there has been increasing concern that the traditional approaches to mechanical ventilation of the ARDS patient may cause a superimposed “iatrogenic” lung injury, and that this ventilator-induced injury may lead to or perpetuate multisystem organ failure through the release of cytokines and other inflammatory mediators from the lung. Such ventilator-induced lung injury may occur, in part, because of repetitive closing and opening of surfactant-deficient and damaged alveoli.<sup>1Amato M.B.P., Barbas C.S.V., Medeiros D.M., et al. Effect of a protective-ventilation strategy on mortality in the acute respiratory distress syndrome N Engl J Med 1998 ;  338 : 347-354 [cross-ref]

Cliquez ici pour aller à la section Références, 40Lachmann B. Open up the lung and keep the lung open Intensive Care Med 1992 ;  18 : 319-321 [cross-ref]

Cliquez ici pour aller à la section Références, 85Verbrugge S.J.C., Lachmann B. Partial liquid ventilation [editorial] Eur Respir J 1997 ;  10 : 1937-1939 [cross-ref]

Cliquez ici pour aller à la section Références</sup> According to this concept, prevention of lung injury may require an “open lung” approach, whereby adequate levels of positive end-expiratory pressure (PEEP) are used to maintain open alveoli at end-expiration in as much of the lung as possible.

The emerging interest in the use of perfluorocarbon liquids to perform “liquid ventilation” is based, in part, on the recognition that this technique potentially fits very well with the new concepts regarding ventilator-induced lung injury in ARDS. Perfluorocarbon liquids may provide a method of maintaining open alveoli (“liquid PEEP”), especially in the most injured, dependent lung zones, which may be otherwise difficult to recruit effectively and safely (e.g., avoiding damage in the less atelectatic, nondependent zones) with traditional “gas PEEP.” There is increasing evidence that perfluorocarbon liquids may substantially ameliorate lung injury through direct anti-inflammatory properties, as well.