Pushing the Envelope of Hypoxemia: Blood Oxygen Depletion in Elephant Seals

海象是海豹和海狮中首屈一指的潜水员；它通常会屏住呼吸20分钟，潜入超过400米的深度。这个项目调查了让这只海豹做出如此非凡潜水的生理学。特别是，据推测，这些海豹可以承受极低的氧气水平，这使得它们在潜水时几乎完全耗尽了血液中的氧气。这种对低氧水平的极端耐受超出了任何哺乳动物的承受能力，远低于试图在没有补充氧气的情况下攀登珠穆朗玛峰的人类的氧气水平。为了验证这一假设，海豹将配备背包式氧气记录器，当海豹潜水时，它将提供血液中氧气压力的轮廓。预计到潜水结束时，血液中的氧气水平将接近于零，正是这种对血液氧气的近乎完全的利用，才使象海豹能够像它们一样潜水。这项研究将确定这些海豹将自己推到的生理极限。这与它们在水下成功找到猎物的能力有关，也与它们在可能因过度捕捞和全球变暖而发生变化的环境中的整体生态有关。此外，允许海豹耐受如此低的氧气水平的机制可能与我们理解和治疗人类组织暴露在氧气不足或血液流动不足(低氧血症或缺血)的各种病理状态有关。最后，除了让学生直接参与研究外，该项目还将开发一个教育网站，提供有关深潜鲸、海豹、企鹅和海龟的行为和生理信息。

The elephant seal is the premier diver among seals and sea lions; it routinely holds its breath for 20 minutes as it dives to depths greater than 400 meters. This project investigates the physiology that allows this seal to make such remarkable dives. In particular, it is hypothesized that these seals can withstand extremely low levels of oxygen, and that this allows them to almost completely deplete their blood of oxygen during diving. Such extreme tolerance to low levels of oxygen is beyond that found in any mammal, and well below the oxygen levels found in humans attempting to climb Mt Everest without supplemental oxygen. In order to examine this hypothesis, seals will be equipped with backpack oxygen recorders which will provide a profile of the oxygen pressure in the blood as the seal dives. It is expected that the oxygen levels in the blood will be near zero by the end of the dive, and that it is this nearly complete utilization of the blood oxygen which allows elephant seals to dive as well as they do. This study will establish the physiological limits to which these seals push themselves. This is relevant to their ability to successfully find prey underwater and to their overall ecology in an environment that may be changing due to over fishing and global warming. In addition, the mechanisms which allow the seals to tolerate such low oxygen levels may be relevant to our understanding and treatment of various pathological states in humans in which tissues are exposed to inadequate oxygen or blood flow (hypoxemia or ischemia). Lastly, in addition to involving students directly in the research, this project will develop an educational website which will provide behavioral and physiological information on deep-diving whales, seals, penguins, and sea turtles.