ABG report explain in short
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ABG arterial blood gas interpretation normal values 2025
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Here is a short, clear explanation of an ABG report:
ABG (Arterial Blood Gas) Report - Explained
An ABG is a blood test taken from an artery (usually the radial artery at the wrist). It measures how well your lungs and kidneys are maintaining the balance of oxygen, carbon dioxide, and acid-base status in your blood.
Key Parameters & Normal Values
| Parameter | Full Name | Normal Range | What It Tells You |
|---|---|---|---|
| pH | Acidity/Alkalinity | 7.35 - 7.45 | Overall acid-base balance of blood |
| PaO2 | Partial pressure of Oxygen | 80 - 100 mmHg | How much oxygen is dissolved in blood |
| PaCO2 | Partial pressure of CO2 | 35 - 45 mmHg | Respiratory component; CO2 is an acid |
| HCO3- | Bicarbonate | 22 - 26 mEq/L | Metabolic (kidney) component |
| SaO2 | Oxygen saturation | >95% | % of hemoglobin carrying oxygen |
| BE | Base Excess | -2 to +2 mEq/L | Excess or deficit of base in blood |
How to Interpret: 4-Step Approach
Step 1 - Check pH
- pH < 7.35 = Acidosis (blood too acidic)
- pH > 7.45 = Alkalosis (blood too alkaline)
Step 2 - Find the Cause
| Disorder | pH | PaCO2 | HCO3- |
|---|---|---|---|
| Respiratory Acidosis | ↓ | ↑ (>45) | Normal |
| Respiratory Alkalosis | ↑ | ↓ (<35) | Normal |
| Metabolic Acidosis | ↓ | Normal | ↓ (<22) |
| Metabolic Alkalosis | ↑ | Normal | ↑ (>26) |
Step 3 - Check for Compensation
The body tries to correct pH imbalance:
- Lungs compensate for metabolic problems (fast, within minutes-hours)
- Kidneys compensate for respiratory problems (slow, takes 2-5 days)
If both PaCO2 and HCO3- are abnormal in opposite directions, compensation is occurring. If within the normal pH range (7.35-7.45), it is fully compensated; if still outside normal range, it is partially compensated.
Step 4 - Assess Oxygenation
- PaO2 < 80 mmHg = Hypoxemia (low oxygen)
- PaO2 < 60 mmHg = Severe hypoxemia - requires immediate oxygen therapy
Common Clinical Examples
| Condition | pH | PaCO2 | HCO3- |
|---|---|---|---|
| COPD / Hypoventilation | ↓ | ↑ | ↑ (compensated) |
| Anxiety / Hyperventilation | ↑ | ↓ | Normal |
| Diabetic Ketoacidosis (DKA) | ↓ | ↓ (compensated) | ↓↓ |
| Vomiting / NG suction | ↑ | ↑ (compensated) | ↑↑ |
Quick Memory Aid
- PaCO2 = Respiratory acid (lungs control it - breathe out CO2)
- HCO3- = Metabolic base (kidneys control it)
- If pH and PaCO2 move in opposite directions = respiratory problem
- If pH and HCO3- move in the same direction = metabolic problem
Sources: Murray & Nadel's Textbook of Respiratory Medicine; Tintinalli's Emergency Medicine
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