How do you find the dissolved O2 content give plasma PO2 and Hb content?

PO2 can be estimate of dissolve O2,PO2 keep the oxygen on hemoglobin so if there is increase affinity of oxygen then required PO2 willbe low.each HB carry 20vol% O2 per 100ml of blood in a 100% saturation.if the dissolve oxygen become less then PO2 also become less in order to deliver more dissolve form to tissues.actua;;u ddissolve O2 at 100mmhg of PO2 is 0.3vol%/100ml of blood