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

海象是海豹和海狮中最好的潜水员;当它潜入400米深的时候，它通常会屏住呼吸20分钟。 这个项目调查的生理学，使这种海豹作出如此显着的潜水。特别是，据推测，这些海豹可以承受极低的氧气水平，这使得他们几乎完全耗尽他们的血液中的氧气在潜水。 这种对低氧水平的极端耐受性超过了任何哺乳动物，并且远低于试图在没有补充氧气的情况下攀登珠峰峰的人类的氧气水平。 为了检验这一假设，海豹将配备背包氧气记录器，它将提供海豹潜水时血液中氧气压力的分布。 预计在潜水结束时，血液中的氧气水平将接近于零，正是这种几乎完全利用血液中的氧气的方式使海象能够像它们那样潜水。 这项研究将建立这些海豹推动自己的生理极限。 这与它们在水下成功寻找猎物的能力以及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，允许密封耐受这种低氧水平的机制可能与我们对人体各种病理状态的理解和治疗有关，在这些病理状态下，组织暴露于氧气或血流不足（低氧血症或缺血）。 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，提供有关深潜鲸鱼、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.