- provides an assessment of alveolar-capillary gas exchange.
- normal gradient is 20 - 65; Gradients > than 400 = severe Resp distress;
- calculation requires: paO2 & PAO2;
- place on 100% O2 for 20 min; PAO2 then = 673 (pCO2 = 47)
- then get @O3.HLX^LABABG[ABG and calc difference; 673 - pO2.
- note: normal Aa grad: = 60-80 mm Hg. normal pO2 on 100% = 600 - 620 mm Hg.
- may also calculate Aa grad on room air, FiO2 = 21%