Liquid breathing

Liquid breathing is a postulated form of respiration in which a normally air-breathing organism breathes an oxygen-rich liquid (such as a perfluorocarbon), rather than breathing air.

Approaches

Total liquid ventilation

Total liquid ventilation (TLV) is completely filling liquid in the lungs, the necessity for the liquid filled tube system contains pumps and heater and membrane oxygenator to deliver and remove tidal volume aliquots of conditioned perfluorocarbon to the lungs.

Partial liquid ventilation

Partial liquid ventilation (PLV) is a technique in which a PFC is instilled into the lung to a volume approximating functional residual capacity (approximately 40% of TLC (Total Lung Capacity)). This mode of liquid ventilation is technically more viable than total liquid ventilation as it can utilize technology currently in place in neonatal intensive care units (NICU) worldwide. The influence of PLV on oxygenation, carbon dioxide removal and lung mechanics has been investigated in several animal studies using different models of lung injury.

Proposed uses

Diving

In diving, the pressure inside the lungs must effectively equal the pressure outside the body, otherwise the lungs collapse. Since external and internal pressures must be equal, the required gas pressure increases with depth to match the increased external water pressure, rising to around 13 bar at 400 feet (120m), and around 500 bar on the oceans' abyssal plains. These high pressures may have adverse effects on the body, especially when quickly released (as in a too-rapid return to the surface), including air emboli and decompression sickness (colloquially known as "the bends").

Space travel

Liquid immersion provides a way to reduce the physical stress of G forces. Forces applied to fluids are distributed as omnidirectional pressures. Because liquids cannot be practically compressed, they do not change density under high acceleration such as performed in aerial maneuvers or space travel. A person immersed in liquid of the same density as tissue has acceleration forces distributed around the body, rather than applied at a single point such as a seat or harness straps. This principle is used in a new type of G-suit called the Libelle G-suit, which allows aircraft pilots to remain conscious and functioning at more than 10 G acceleration by surrounding them with water in a rigid suit. An astronaut totally immersed in liquid, with liquid inside all body cavities, will feel little effect from extreme G forces because the forces on a liquid are distributed equally, and in all directions simultaneously. However effects will be felt because of density differences between different body tissues, so an upper acceleration limit still exists.

To be continued...

References:

1. Kylstra JA (1977). The Feasibility of Liquid Breathing in Man. Report to the US Office of Naval Research. Durham, NC: Duke University.
2. Shaffer, T.H., M.R. Wolfson, and L.C. Clark: State of art review : Liquid ventilation. Pediatr. Pulmonol. 14:102 109, 1992.
3. Libros R, CM Philips, MR Wolfson, and TH Shaffer: A perfluorochemical loss/restoration(L/R) system for tidal liquid ventilation. Biomed Instrum & Technol. 34(5): 351-360, 2000.
4. Heckman, JL, J Hoffman, TH Shaffer, and MR Wolfson: Software for real-time control of a tidal liquid ventilator. Biomedical Instrumentation & Technology 33(3):268-276, 1999.