Effectiveness of oxygen therapy in hypoxic polycythemic smokers

Eleven hypoxic (arterial oxygen pressure [PaO2] less than or equal to 61 mm Hg), polycythemic (hematocrit reading greater than or equal to 54 percent) patients were studied to determine the effect of the carboxyhemoglobin level on their response to therapy with supplemental oxygen. Five nonsmokers with a mean carboxyhemoglobin level of 2.8 percent showed an excellent response to therapy with supplemental oxygen, with a decrease in hematocrit reading from 57 percent to 48 percent (P less than 0.0025) as the PaO2 increased from 53 mm Hg to 69 mm Hg (P less than 0.01) and the arterial oxygen saturation (SaO2) increased from 86 percent to 94 percent (P less than 0.0025). Six smokers with a mean carboxyhemoglobin level of 13 percent showed an incomplete response to therapy with supplemental oxygen, with a decrease in hematocrit reading from 62 percent to 57 percent (P less than 0.0025) as the PaO2 increased from 53 mm Hg to 69 mm Hg (P less than 0.0025) and the SaO2 increased from 82 percent to 88 percent (P less than 0.001). In spite of similar values for the PaO2, the smokers had higher hematocrit readings before and during therapy with oxygen (P less than 0.01), presumably due to superimposed desaturation by carboxyhemoglobin. We concluded that polycythemia in hypoxic smokers is due to additive effects of hypoxia and a high carboxyhemoglobin level. The former is responsive to therapy with oxygen, while the latter is not. To achieve a "complete" response to therapy with supplemental oxygen, hypoxic polycythemic smokers should quit smoking.