It goes: the pressure gradient against a conc"n gradient, gas in solution, total volume of gas in blood depends on its solubility in accordance with. 100 mm hg: 1 gram of hb carries betw 1. 34 1. 39 ml o2, w/ [hb] = 15 gm/100 ml blood, blood increases o2 content to 20 ml o2 per 100 ml blood (67x increase). Varate/qrate differences for example) causes very little change in blood. Causes decr in pto2 (larger p gradient into tissues). Drops below 40 mm hg, and makes a big difference b/c it"s at steep part of curve. 12 of otis h/o: pao2 initially decreases at start of inspiration. This is due to 3 mechanisms: alveolar tidal volume is usually much less than frc so gas tension changes are buffered, bf through lung increases during inspiration so increase in. Pao2 is attenuated by higher rate of transfer into blood for a perfusion-limited gas.