PULSE OXIMETRY CORRECTION FOR SMOKING EXPOSURE

Pulse oximetry oxygen saturation (SpO(2)) does not distinguish carboxy hemoglobin (COHb) from oxyhemoglobin (O(2)Hb), giving a false impressi on of the apparent degree of oxyhemoglobin saturation in smokers who h ave elevated levels of COHb, We questioned whether accounting for smok ing exposure history could improve description of pulse oximetry by co rrecting for COHb levels, We evaluated smoking history and %SpO(2) as predictors of %O-2,Hb and %COHb by CO-oximetry of arterial blood in 18 actively smoking and 18 age-matched nonsmoking patients in a clinical pilot study. The difference between %SpO(2) and %O(2)Hb was significa ntly greater (p < 0.001) in the smokers (5.6 +/- 3.1) than the nonsmok ers (2.1 +/- 2.1). This difference correlated with %COHb (r(p) = 0.789 ; p < 0.001) and the smoking exposure score (SES, r(p) = 0.621; p < 0. 001), a six-point index we developed based on whether patients mere ac tive smokers, refrained from smoking prior to testing, or were exposed to passive smoking in the home or workplace, The following formula su mmarizes the correction: %O(2)Hb = 0.882[%SpO(2)] - 0.968[SES] + 9.245 (r(p) = 0.841; SES = 2.478; p < 0.001). This pilot study suggests tha t smoking exposure history correlates with COHb levels and that correc tion for smoking exposure improves the accuracy of pulse oximetry.