What Is Liquid Breathing?

Liquid ventilation is a ventilation technology in which oxygen-carrying liquid is infused into the lungs through organs to replace gas for oxygen and carbon dioxide exchange. Different from the principle of conventional gas exchange, LV technology uses the oxygen-carrying liquid to form a liquid-liquid interface at the alveolar membrane.

Liquid ventilation

In the last century, Winternith et al. Found that infusion of physiological saline solution into the lungs can restore lung function, and Neegard found that saline-filled lungs can eliminate the air-liquid interface of the alveoli, thereby reducing alveolar surface tension. Kylstra tried to immerse the animal in a high-pressure oxygenated salt solution and found that the animal can breathe in liquids and return to normal breathing after the experiment. Based on this research, the concept of LV was proposed. However, high pressure saline perfusion of the lung can maintain normal arterial blood oxygen partial pressure, but it is often accompanied by carbon dioxide retention. In addition, a large amount of saline lavage will wash out alveolar surfactants, so this method is still difficult to be applied clinically. Later, some people used oil as a medium, but it was discarded because of its high viscosity, limited oxygen carrying capacity, and low volatility.

In 1966 Clark et al. Found that perfuorocarbons (PFCs) have the advantages of high solubility in oxygen and carbon dioxide, stable properties, do not react with living tissues, small intermolecular interactions, and low surface tension, and are excellent media for LV. Through extensive experimental research, Greenspan et al. Successfully applied total liquid ventilation (TLV) technology to the clinic for the first time in 1989. In order to overcome the disadvantages of complicated TLV operation, Fuhrman et al. Proposed a simpler and more effective liquid ventilation method, namely partial liquid ventilation (PLV), through improvement. This method makes LV technology possible in clinical applications.

A large number of studies have shown that the therapeutic effects of LV include the following aspects: better oxygen-carrying and carbon dioxide capacity, which plays a role in gas transport in the lung; anti-inflammatory effect; positive end-expiratory pressure of liquid , PEEP), reopen the collapsed alveoli, reduce alveolar tension, and reduce dead space; Due to the gravity of PFCs, the blood flow in the upper and lower areas of the lungs is redistributed, especially the blood flow in the sagging area is reduced, thereby Improve lung ventilation / blood flow ratio.

The possible pathophysiological mechanisms for LV to play its role are: promote the production of endogenous alveolar surfactants; facilitate the discharge of alveolar and small airway secretions; stabilize the cell membrane and inhibit the release of inflammatory mediators, thereby inhibiting lung tissue The inflammatory response prevents or reduces lung injury.