Normal Blood Gases : Arterial Blood Gases : Online Medical Help

Arterial Blood Gases Arterial blood gas analysis provides information on the following: 1] Oxygenation of blood through gas exchange in the lungs.  2] Carbon dioxide (CO2) elimination through respiration.  3] Acid-base balance or imbalance in extra-cellular fluid (ECF).   Normal Blood Gases
	Arterial	Venous
pH	7.35 - 7.45	7.32 - 7.42
Not a gas, but a measurement of acidity or alkalinity, based on the hydrogen (H+) ions present. The pH of a solution is equal to the negative log of the hydrogen ion concentration in that solution: pH = - log [H+].
PaO2	80 to 100 mm Hg.	28 - 48 mm Hg
The partial pressure of oxygen that is dissolved in arterial blood. New Born – Acceptable range 40-70 mm Hg.  Elderly: Subtract 1 mm Hg from the minimal 80 mm Hg level for every year over 60 years of age:  80 - (age- 60)  (Note: up to age 90)
HCO3	22 to 26 mEq/liter (21–28 mEq/L)	19 to 25 mEq/liter
The calculated value of the amount of bicarbonate in the bloodstream. Not a blood gas but the anion of carbonic acid.
PaCO2	35-45 mm Hg	38-52 mm Hg
The amount of carbon dioxide dissolved in arterial blood.  Measured.  Partial pressure of arterial CO2.  (Note: Large A= alveolor CO2).  CO2 is called a “volatile acid” because it can combine reversibly with H2O to yield a strongly acidic H+ ion and a weak basic bicarbonate ion (HCO3 -) according to the following equation: CO2 + H2O <--- --> H+  +  HCO3
B.E.	–2 to +2 mEq/liter Other sources:  normal reference range is between -5 to +3.
The base excess indicates the amount of excess or insufficient level of bicarbonate in the system.  (A negative base excess indicates a base deficit in the blood.) A negative base excess is equivalent to an acid excess. A value outside of the normal range (-2 to +2 mEq) suggests a metabolic cause for the abnormality.  Calculated value.  The base excess is defined as the amount of H+ ions that would be required to return the pH of the blood to 7.35 if the pCO2 were adjusted to normal.  It can be estimated by the equation: Base excess = 0.93 (HCO3 - 24.4 + 14.8(pH - 7.4)) Alternatively: Base excess = 0.93×HCO3 + 13.77×pH - 124.58 A base excess > +3 = metabolic alkalosis a base excess < -3 = metabolic acidosis
SaO2	95% to 100%	50 - 70%
The arterial oxygen saturation.