Table 4.1-1. Parameters of arterial blood gas analysisa

Symbol

Definition

Normal range

pH

Negative logarithm of hydrogen ion concentration

7.35 to 7.45

PaCO2

Arterial level of carbon dioxide

32 to 45 mm Hg (4.27-6.00 kPa)

HCO3curr

Current plasma bicarbonate level

21 to 27 mmol/L

HCO3std

Standard plasma bicarbonate level

24 (21-25) mmol/L

BE

Base excess in blood

−2.3 to +2.3 mEq/L

PaO2

Arterial oxygen level

75 to 100 mm Hgb (10.00-13.33 kPa)

ctCO2

Total plasma content of carbon dioxide

22 to 28 mmol/L

47.0% to 60.5% (volume)

SaO2

Oxygen saturation of hemoglobin in arterial blood

95% to 98%b

a Blood drawn without contact with air.

b When interpreting PaO2 and SaO2, always record the fraction of inspired oxygen (FiO­2). The normal ranges given here are for respiration with atmospheric air at sea level (an oxygen concentration of 20.9%, which corresponds to an FiO­2 of 0.209). When a healthy individual is breathing 100% oxygen (FiO­2 = 1.0), PaO2 may be as high as ~600 mm Hg and SaO2 may reach 100%.