Introduction to Respiratory Care/Arterial blood gases
Many methods exist to guide the interpretation of the ABG.
Step 1: Henderseon-Hasselbach equation
edit[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?
editpH < 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)