来自《耶鲁大学开放课程：生物医学工程探索 第13集 第13集》

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  but that's the range of pressures in your circulatory system
  循环系统中血压的范围大概就是
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  from 0 mmHg up to 120 mmHg; roughly
  从零毫米汞柱到一百二十毫米汞柱
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  and we'll see you go outside that range sometimes.
  有时会超过这个范围
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  Now these are pressures
  这就是循环系统内部
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  that are inside our circulatory system so they must be--
  压强的大小 这个压强必须
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  but they're only a fraction of 1 atm, how can that be?
  这不到一大气压 怎么会这样
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  An atm is 760 mmHg,
  一个大气压是七百六十毫米汞柱
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  that's the pressure in this room.
  屋里的压力就这么大
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  If your blood pressure is 120/80 what does that mean?
  如果你的血压是120/80的话会怎样
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  Well, pressure is--we only care about differences in pressure.
  压强是 我们只关注压差
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  It's relative pressure that matters not the absolute pressure.
  相对压力更有意义 而不是绝对压力
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  When you say your blood pressure is 120/80 that means
  说血压为 120/80 的意思是