Short-term isocapnic hypoxia and coagulation activation in patients with sleep apnea

Hemostatic changes might contribute to the increased risk of cardiovascular and cerebrovascular events in patients with obstructive sleep apnea (OSA). We investigated the effect of a short-term isocapnic hypoxic challenge on coagulation activation markers thrombin/antithrombin III complexes (TAT) and D-dimer in OSA. Thirty-two OSA patients (mean age 48 +/- 11 years) inhaled a gas mixture containing 10% O(2) and 90% N(2) and further adjusted to yield pulse oximetry saturation of 80-85% for 5 minutes. Plasma levels of TAT and D-dimer were measured immediately before and immediately after the hypoxic challenge. The hypoxic challenge provoked a significant increase in TAT (p < 0.001) and in D-dimer (p = 0.037). Mean nocturnal oxygen saturation from the sleep recordings correlated with D-dimer increase (r = -0.37, p = 0.041). Also, OSA patients with a history of hypertensive parents had greater D-dimer increase in response to hypoxia than patients having normotensive parents (p = 0.035). Parental hypertension independently explained 15% of the variance in D-dimer increase after hypoxia (p = 0.035). Oxygen desaturation during sleep may predispose OSA patients, in particular those with a parental history of hypertension, to a hypercoagulable state providing one explanation for the increased risk of atherothrombotic events in this population.