PULSE OXIMETRY IN SEVERE CARBON-MONOXIDE POISONING

Study objectives: To evaluate the accuracy and quantitate the error of pulse oximetry measurements of arterial oxygenation in patients with severe carbon monoxide (CO) poisoning. Design: Retrospective review of patient clinical records, Setting: Regional referral center for hyper baric oxygen therapy, Patients: Thirty patients referred for treatment of acute severe CO poisoning who demonstrated carboxyhemoglobin (COHb ) levels >25%, with simultaneous determinations of arterial hemoglobin oxygen saturation by pulse oximetry (Spo(2)) and arterial blood gas ( ABG) techniques. Measurements and results: COHb levels and measurement s of arterial oxygenation from pulse oximetry, ABG analysis, and labor atory CO oximetry were compared. Spo(2) did not correlate with COHb le vels. Spo(2) consistently overestimated the fractional arterial oxygen saturation. The difference between arterial hemoglobin oxygen saturat ion (Sao,) calculated from ABG analysis and Spo(2) increased with incr easing COHb level. Conclusions: Presently available pulse oximeters ov erestimate arterial oxygenation in patients with severe CO poisoning. An elevated COHb level falsely elevates the Sao, measurements from pul se oximetry, usually by an amount less than the COHb level, confirming a prior observation in an animal model,Accurate assessment of arteria l oxygen content in patients with CO poisoning can currently be perfor med only by analysis of arterial blood with a laboratory CO-oximetry.