HBOT AND CARBON MONOXIDE POISONING

Carbon monoxide (CO) poisoning is a complex event involving more than just the
generation of carboxyhaemoglobin and the subsequent unavailability of haemoglobin
to transport oxygen. CO is a systemic toxin capable of producing hypoxia at the
cellular level in a number of ways. First, CO has an affinity for haemoglobin
approximately 200 to 250 times greater than oxygen’s. Therefore, even in
environments containing only small quantities of CO, haemoglobin rapidly binds CO
and becomes unavailable for the transportation of oxygen. CO also binds to other
haeme pigments such as myoglobin. Second, once bound to haemoglobin, CO
adversely affects the oxygen-haemoglobin dissociation curve, shifting it to the left.
Oxygen already combined with haemoglobin becomes more firmly attached and a
tissue oxygen tension much lower than normal is required before the oxygen is
released, thus leading to tissue hypoxia. Lastly, once in the mitochondria, CO binds
to the cytochrome oxidase enzymes responsible for cellular respiration, especially
cytochrome a,a3
, the terminal enzyme in the electron transport chain. This
inhibits the final step in oxidative phosphorylation – the energy transfer from the
formation of metabolic water required for the production of ATP from ADP. The end
result is oxygen becomes less available to meet the cell’s metabolic needs and death
by cellular anoxia results with the release of cytochrome C and large amounts of
reactive oxygen species as the terminal events. . In fires there may be a complex
mixture of fumes such as carbon monoxide, cyanide and other gases. Cyanide
inhaled in this combination with carbon monoxide and smoke inhalation is a
recommended indication for hyperbaric oxygen therapy, since it could be fatal as a
result of cytotoxic hypoxia, which leads to organ dysfunction and possibly death[.
Hyperbaric oxygen therapy is approved and recommended for the treatment of
selected cases of CO poisoning
HBO therapy has been approved by many authors during the last 30 years and is considered urgent and strongly recommended. The best  results are obtained when HBO therapy is started within 6 hours after intoxication after giving normobaric oxygen as a first aid and follow up of neurological, cardiological and behavioural changes.