Table 1.

Atmospheric/ambient pressures under different baric conditions and corresponding oxygen tensions in alveoli, arteries, extracellular fluids of tissues, and mitochondria. ATA = atmospheres absolute; AP = atmospheric pressure; PO₂ = partial pressure of oxygen; PAO₂ = partial pressure of oxygen in alveoli; PaO₂ = partial pressure of oxygen in arteries; PtO₂ = partial pressure of oxygen in tissues; PmO₂ = partial pressure of oxygen in mitochondria. * Estimations through extrapolations.

Atmospheric/Ambient		Oxygen Tension of Inspired Air, PO2	Oxygen Tension in Alvoli, PAO2	Oxygen Tension in Arteries, PaO2	Oxygen Tension in Tissues, PtO2	Oxygen Tension in Mitochondria, PmO2
Pressure (AP) mmHg		mmHg	mmHg	mmHg	mmHg	mmHg
2.5 ATA, AP 1875
15 m diving, 100% O2 breathing		1875	1284 *	1274	250–500 [58,59]	80–125 *
		236	162 *	152	30–60 *
5 m diving, 100% O2 breathing		1125	771 *	761 (59)	150–304 *	50–76 *
1.3 ATA, AP 988 air breathing		207	158 *	148 [60,61]	30–60 *	10–15 *
3 m diving, 100% O2 breathing		975	668 *	658	130–263 *	45–65 *
Sea level (1.0 ATA), AP 760 mmHg
Air breathing [62,63,64] 20–50 y		160	102–110	97–99	20–40	7.5–11
	>64 y	-”-	-”-	82–93	16–37 *
100% O2 breathing [63,64]		760	674	516	207 *	77 *
Dead Sea * −457 m AP 802 mmHg		167	114	104	42	15
Air