pH

Arterial blood gas results are used to assess tissue oxygenation, ventilation and acid-base status. Parameters included in a blood gas are: pH, PO₂, PCO₂, base excess, and bicarbonate. PH measures the hydrogen concentration of blood. A Sanz electrode with pH sensitive glass measures the change in hydrogen concentration across the pH sensitive glass membrane.

Reference range for blood pH is 7.35-7.45. Acidemia is present if the pH is less than 7.35 and alkalemia is present if pH is greater than 7.45. Critical values for blood pH are <7.20 and >7.60. 

Specimen requirement is 3 mL of whole blood in a heparinized syringe.  If the specimen cannot be immediately sent to the laboratory it should be placed in wet ice.

For more information on metabolic acidosis, see the article entitled: “Anion Gap.”

Reference

Hopkins E, Sanvictores T, Sharma S, Physiology, Acid Base Balance, StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507807/