[Effects of nCPAP therapy on the blood picture in patients with obstructive sleep apnea].

In some patients with obstructive sleep apnea, changes in red blood cell count resembling polycythemia can be observed. If these changes result from the sleep-related breathing disorder, its adequate treatment should in turn induce a decrease of, for instance, hemoglobin concentration. We therefore set out by examining retrospectively the development of hemoglobin concentration under nCPAP in 130 patients with polysomnographically verified obstructive sleep apnea, comparing the values before treatment and after a mean of 12.0 months. During this period, hemoglobin mass concentration dropped from a mean of 153 +/- 13 g/Ls to 148 +/- 11 g/Ls (p < 0.001). Afterwards we prospectively examined in 50 patients the changes in complete blood cell count before and immediately after initiation of nCPAP treatment. It turned out that hemoglobin mass concentration dropped from a mean of 154 +/- 14 g/Ls to 148 +/- 14 g/Ls (p < 0.001), the erythrocyte count from 5.02 +/- 0.42/pl to 4.79 +/- 0.51/pl (p < 0.001), and hematocrit from 45.4 +/- 3.1% to 43.1 +/- 4.3% (p < 0.001) after only one night; no more significant change occurred after that. Increased hemoglobin mass concentrations, erythrocyte counts and hematocrit values can be the result of obstructive sleep apnea. Treatment of this sleep disorder with nCPAP will induce a quick and significant decrease of hemoglobin mass concentration, erythrocyte count, and hematocrit, independent of the initial values. This phenomenon points to the fact that changes in blood cell counts are not caused by a disturbance of erythropoesis but rather by alterations in volume regulation.