Bradford A
Department of Physiology, Royal College of Surgeons in Ireland, St. Stephen's Green, Dublin 2, Ireland.
Curr Pharm Des. 2007;13(26):2668-72. doi: 10.2174/138161207781662966.
Although somewhat controversial, there is good evidence that long-distance travel in general is a risk factor for venous thromboembolism, even in the absence of other risk factors. This is probably due to effects consequent to prolonged sitting but air travel in particular may be associated with risk factors other than this. One likely factor is hypoxia caused by the low ambient pressure of aircraft cabins. There is an association between venous thromboembolism and the hypoxia of altitude, chronic respiratory disease, neonatal hypoxia, sleep apnoea and experimentally-induced hypoxia. Platelet number and/or function are altered in all of these circumstances. Platelet aggregation is pivotal to venous thromboembolism and hypoxia alters platelet number and function. The early-onset thrombocytosis caused by hypoxia may be due to increased release of platelets from megakaryocytes and the late-onset thrombocytopaenia may be due to decreased platelet production and/or stem cell competition between erythrocytes and megakaryocytes. Hypoxia-induced platelet activation and aggregation may be due to increased circulating catecholamine levels but it is not known whether hypoxia can affect platelets directly. There is a need for further studies on the possible involvement of hypoxia-induced changes in platelet number and function in air travel-related venous thromboembolism.
尽管存在一定争议，但有充分证据表明，一般而言长途旅行是静脉血栓栓塞的一个风险因素，即使不存在其他风险因素也是如此。这可能是由于长时间坐着导致的影响，但特别是航空旅行可能还与除此之外的其他风险因素有关。一个可能的因素是机舱内环境压力低所导致的缺氧。静脉血栓栓塞与高原缺氧、慢性呼吸道疾病、新生儿缺氧、睡眠呼吸暂停以及实验诱导的缺氧之间存在关联。在所有这些情况下，血小板数量和/或功能都会发生改变。血小板聚集对于静脉血栓栓塞至关重要，而缺氧会改变血小板数量和功能。缺氧引起的早期血小板增多症可能是由于巨核细胞释放血小板增加所致，而晚期血小板减少症可能是由于血小板生成减少和/或红细胞与巨核细胞之间的干细胞竞争所致。缺氧诱导的血小板活化和聚集可能是由于循环中儿茶酚胺水平升高，但尚不清楚缺氧是否能直接影响血小板。有必要进一步研究缺氧引起的血小板数量和功能变化在与航空旅行相关的静脉血栓栓塞中可能所起的作用。
