There is some evidence for a hypercoagulable state in sleep apnea-hipopnea syndrome (SAHS), which could play a role in the increased cardiovascular morbility and mortality. Respiratory alterations (hypoxia, hypoxia- reoxygenation) and sleep fragmentation that these patients suffer during the sleep may induce modifications in clotting-fibrinolisis factors that may be a risk factor for venous thromboembolism (VTE).