Introduction to Respiratory Care/Arterial blood gases

Many methods exist to guide the interpretation of the ABG.

Step 1: Henderseon-Hasselbach equationEdit

[H+] = 24(PaCO2) / [HCO3-]

If the pH and the [H+] are inconsistent, the ABG is probably not valid.

pH Approximate [H+] (mmol/L)
7.00 100
7.05 89
7.10 79
7.15 71
7.20 63
7.25 56
7.30 50
7.35 45
7.40 40
7.45 35
7.50 32
7.55 28
7.60 25
7.65 22

Is there alkalemia of acidemia present?Edit

pH < 7.35  acidemia
pH > 7.45  alkalemia
  • This is usually the primary disorder
  • You will need to check the PaCO2, HCO3- and anion gap
  • An acidosis or alkalosis may be present even if the pH is in the normal range (7.35 – 7.45)

Respiratory vs. MetabolicEdit

CompensationEdit

Increased anion gapEdit

Last modified on 18 March 2012, at 22:33