due to involvement of chemoreceptors, ph buffers and other physiochemical functionalities). carbon monoxide poisoning disturbs this physiological process hence the venous blood of poisoning patients is bright red akin to arterial blood since the carbonyl/carbon monoxide is retained, whereas deoxygenated hemoglobin is dark red and carbaminohemoglobin has a blue hue. at toxic concentrations, carbon monoxide as carboxyhemoglobin significantly interferes with respiration and gas exchange by simultaneously inhibiting acquisition and delivery of oxygen to cells, and preventing formation of carbaminohemoglobin which accounts for approximately 30% of carbon dioxide exportation. therefore a patient suffering from carbon monoxide poisoning may experience severe hypoxia and acidosis in addition to the toxicities of excess carbon monoxide binding to numerous hemoproteins, metallic and non-metallic targets which affect cellular machinery (such as inhibition of cytochrome c oxidase). toxicokinetics in common air under normal atmospheric conditions, a typical patient's carboxyhemoglobin has a half-life around 300 minutes. this time can be reduced to 90 minutes upon administration of high-flow pure oxygen, and the time is further reduced when oxygen is administered with 5% carbon dioxide as first identified by esther killick. additionally, treatment in a hyperbaric chamber is a more effective manner of reducing the half-life of carboxyhemoglobin to 30 minutes and allows oxygen to dissolve in biological fluids for delivery to tissues. supplemental oxygen takes advantage of le chatelier's principle to quicken the decomposition of carboxyhemoglobin back to hemoglobin: hbco + o2 ⇌ hb + co + o2 ⇌ hbo2 + co carboxyhemoglobin pharmaceuticals as carbon monoxide is now understood to have a therapeutic potential, pharmaceutical efforts have focused on development of carbon monoxide-releasing molecules and selective heme oxygenase inducers. an alternative method for drug delivery consists of carbon monoxide immobilized on polyethylene glycol (peg)-lyated bovine carboxyhemoglobin which is currently in late clinical development. similarly, maleimide peg conjugated human carboxyhemoglobin had previously been the subject of pharmaceutical development.