Table 1

Relative effects of changes in Pao2, haemoglobin (Hb), and cardiac output (Qt) on oxygen delivery (Do2)

Fio2Pao2 (kPa)Sao2 (%)Hb (g/l)Dissolved O2 (ml/l)Cao2 (ml/l)Qt (l/min)Do2 (ml/min)Do2 (% change)‡
Do2= Cao2 × Qt ml/min, Cao2 = (Hb × Sao2 × 1.34) + (Pao2 × 0.23) ml/l where Fio2 = fractional inspired oxygen concentration; Pao2, Sao2, Cao2 = partial pressure, saturation and content of oxygen in arterial blood; Qt = cardiac output. 1.34 ml is the volume of oxygen carried by 1 g of 100% saturated Hb. Pao2 (kPa) × 0.23 is the amount of oxygen in physical solution in 1 l of blood, which is less than <3% of total Cao2 for normal Pao2 (ie <14 kPa). *Normal 75 kg subject at rest. †Patient with hypoxaemia, anaemia, reduced cardiac output, and evidence of global tissue hypoxia. ‡Change in Do2 expressed as a percentage of the preceding value.
Normal*0.2113.0961303.01705.39000
Patient†0.21 6.075 701.4 724.0288– 68
↑Fio20.35 9.092 702.1 884.0352+ 22
↑↑Fio20.6016.598 703.8 964.0384+ 9
↑Hb0.6016.5981053.81424.0568+48
↑Qt0.6016.5981053.81426.0852+50