Nano Gets Closer

NCBI has reproduced a bunch of bio books on line. Check this section from one of the nanotech volumes (I've edited out a lot of detail):

One very simple nanorobot that I designed a few years ago is the artificial mechanical red cell, which I call a "respirocyte." ... It is a spherical nanorobot made of 18 billion atoms. These atoms are mostly carbon atoms arranged as diamond in a porous lattice structure inside the spherical shell.

The respirocyte is essentially a tiny pressure tank that can be pumped full of up to 9 billion oxygen and carbon dioxide molecules. These gases can be released from the tiny tank in a controlled manner. The gases are stored onboard at pressures up to about 1000 atmospheres.
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What if you added 1 liter of respirocytes into your bloodstream? You could then hold your breath for nearly 4 hours if sitting quietly at the bottom of a swimming pool. Or if you were sprinting at top speed, you could run for at least 15 minutes before you had to take a breath!
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Respirocytes mimic the action of the natural hemoglobin-filled red blood cells. But a respirocyte can deliver 236 times more oxygen per unit volume than a natural red cell. ... (The operating pressure of the natural red blood cell is the equivalent of only about 0.51 atm, of which only about 0.13 atm is deliverable to tissues.) ...