The basic requirement for gas exchange in terrestrial animals is a moist surface or
membranes for gases like oxygen and carbon dioxide to move across. In terrestrial
vertebrates like mammals, this is done through their well-developed respiratory system
with lungs. Their lungs contain microscopic air sacs of alveoli surrounded by blood
vessels used to transport gases for gas exchange(Cliffsnotes,n.d). Mammals can’t
breathe liquid as they do not have gills like fish do. But liquid ventilation may enable
them to breathe through a special liquid medium if the surface tension at the air-liquid
interface of their lungs is increased, like in acute lungs injuries(Kaiser, Kelly,
Busch,2003).
The idea of applying liquid to lungs first appeared in the basic research for treatment of
poison gas inhalation in WW1, which involves applying saline solutions to the lungs of
dogs. Subsequently, the discovery that mammals could breathe through a liquid
medium was founded by Kysltra and his colleagues in the 1960s. In their experiment,
breathing in liquid was studied to increase the escape depth from a submerged
submarine. Mice were immersed in physiological salt solutions and subject to increased
pressures to allow sufficient oxygen to dissolve into the solution. However, the mice all
died within minutes of respiratory acidosis as the work of breathing is very great, so
scientists later uses a medium that could dissolve large amounts of respiratory gases at
atmospheric pressures and is save for the animals- perfluorocarbons (PFCs)(Kaiser,
Kelly, Busch,2003).
Liquid ventilation works by inhaling oxygenated PFC into the lungs or introducing them
intravenously into the circulation. PFC increases oxygen supply to the tissues and acts
as an oxygen reservoir when it is in the circulation with the hemoglobin in RBCs by
releasing its oxygen first, allowing the RBCs to remain partially oxygenated before it
reaches the hypoxic tissues. Although there is no indication that the transport of
dissolved CO2 by PFCs interacts with the CO2 transport mechanism that takes place in
hemoglobin and plasma, clinical and experimental results show the tendency of faster
acid balance recovery when PFCs are in circulation(CABRALES, VÁZQUEZ.,
NEGRETE, INTAGLIETTA,2007).
In terms of application, PFCs rather than nitrogen as the inert carrier of oxygen and
carbon dioxide offers a theoretical benefit as a treatment of acute lung injuries, as well
as a potential for clinical applications in liquid-assisted ventilation in the future(Tawfic,
Kausalya, 2011).
Citation:
Cliffsnotes, Mechanisms for gas exchange[Online]
Available
from:https://www.cliffsnotes.com/study-guides/biology/biology/gas-exchange/mechanis
ms-for-gas-exchange
Accessed: 2nd October 2021
U. Kaisers, K. P. Kelly, T. Busch, Liquid ventilation, BJA: British Journal of Anaesthesia,
Volume 91, Issue 1, July 2003, Pages 143–151
Available from: https://doi.org/10.1093/bja/aeg147
Accessed: 2nd October 2021
Tawfic, Q. A., & Kausalya, R. (2011). Liquid ventilation. Oman medical journal, 26(1),
4–9.
Available from: https://doi.org/10.5001/omj.2011.02
Accessed: 3rd October 2021
CABRALES, P., VÁZQUEZ, B.Y.S., NEGRETE, A.C. and INTAGLIETTA, M. (2007),
Perfluorocarbons as gas transporters for O2, NO, CO and volatile anesthetics.
Transfusion Alternatives in Transfusion Medicine, 9: 294-303.
Available from:https://doi.org/10.1111/j.1778-428X.2007.00085.x
Accessed: 3rd October 2021