PHGY 312 Lecture Notes - Lecture 7: Fraction Of Inspired Oxygen, Swimming Pool, Blood Gas Tension
24 May 2016
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Content depends on solubility of the gases (co2>>>28x more soluble than o2) Paco2 = (vco2/va) pb, pao2 = (fio2- vo2/va) pb. Po2 is 150 mmhg in the water and the air but solubility is 0. 5% in the water (20. 9% in the air) Pressure, not the content of o2, that allows us to breathe. Carrier of oxygen, hb, increases solubility of oxygen up to 20 times. As h+ increases or rise in temperature, we have an increase in hb unloading. Small species have a high p50 and large species have a low p50. Small needs more o2/unit tissue to have a high p50 helps. In anemia or hemorrhage, hb goes down so the hb curve shifts down. Co has enormous affinity for hb (200x higher) Chemoreceptors cannot detect this, because it"s not a change in pressure, but concentration. The loss of 5 ml = decrease of 60 mmhg, bringing us to po2 of 40 mmhg.
