Supplemental oxygen is indicated when normal oxygenation is impaired because of pulmonary injury, which may result from aspiration (chemical pneumonitis) or inhalation of toxic gases. The Po2 should be maintained at 70– 80 mm Hg or higher if possible.
Supplemental oxygen usually is given empirically to patients with altered mental status or suspected hypoxemia.
Oxygen (100%) is indicated for patients with carbon monoxide poisoning to increase the conversion of carboxyhemoglobin and carboxymyoglobin to hemoglobin and myoglobin, respectively, and to increase the oxygen saturation of the plasma and subsequent delivery to tissues.
Hyperbaric oxygen may be beneficial for patients with severe carbon monoxide poisoning, although the clinical evidence is mixed. Potential indications include history of a loss of consciousness, metabolic acidosis, age older than 36 years, pregnancy, carboxyhemoglobin level greater than 25%, and cerebellar dysfunction (eg, ataxia; see Table II–19).
Hyperbaric oxygen has also been advocated for the treatment of poisoning with carbon tetrachloride, cyanide, and hydrogen sulfide and for severe methemoglobinemia, but the experimental and clinical evidence is scanty.