Siemens Rapidlab 1200 Operator's Manual page 54

1-34
Using this formula, a hydrogen ion concentration of 1 x 10
Because pH is the negative logarithm, its value is inversely proportional to the actual
hydrogen ion concentration in a sample. Therefore, as the hydrogen ion concentration
decreases, the pH value increases. As the hydrogen ion concentration increases, the pH
value decreases.
The normal pH range of human blood is 7.35–7.45.
The Henderson-Hasselbalch equation describes how pH expresses the interaction of acid
and base in blood:
=
pH
where K is the dissociation constant, which describes the ability to release hydrogen ions.
Because K, and thus pK, is a constant, this equation can be used to demonstrate that pH is
proportional to the acid-base concentrations in blood:
α
pH
Therefore, if base increases without a corresponding increase in acid, the pH rises, and if
acid increases without a corresponding increase in base, the pH decreases.
pH is clinically significant as a means of determining acid-base disturbances. Acid-base
disorders can result in several pathologic conditions. Acidosis (low pH) stems from either
respiratory failure (high pCO
acidosis, uremia, severe diarrhea, hypoaldosteronism, renal tubular disease, drug effects,
or poisoning from several specific agents). Alkalosis (high pH) stems from
hyperventilation (low pCO
gastric drainage, drug effects, hyperadrenocorticism, potassium depletion, or excessive
alkali intake). Extreme abnormalities of pH reflect a potentially life-threatening
pathophysiologic state that must be corrected promptly.
02087462 Rev. V
Rapidlab 1200 Operator's Guide: System Overview and Intended Use
base
+
pK log
acid
base
acid
2
) or from metabolic causes (including excessive vomiting,
2
) or from metabolic causes (including ketoacidosis, lactic
-7
mol/L has a pH value of 7.
6,7