RT Priority
Continue routine assessment and use this ABG as a baseline comparison for abnormal cases.
Patient 1
A 22-year-old patient is awake and comfortable in post-procedure recovery after brief sedation. The care team reviews an ABG obtained during recovery because the patient briefly required supplemental oxygen earlier.
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Learning Objectives
By the end of this case, learners should be able to interpret the ABG in a complete, clinically useful format.
1. Classify pH
Determine whether the patient is acidotic, alkalotic, or normal.
Determine whether the patient is acidotic, alkalotic, or normal.
2. Identify the primary pattern
Decide whether the disorder is respiratory, metabolic, or absent.
Decide whether the disorder is respiratory, metabolic, or absent.
3. Assess compensation
Determine whether compensation is absent, partial, complete, or not applicable.
Determine whether compensation is absent, partial, complete, or not applicable.
4. Assess oxygenation
Use PaO₂ to classify oxygenation status.
Use PaO₂ to classify oxygenation status.
Clinical Picture
A 22-year-old patient is awake and comfortable in post-procedure recovery after brief sedation. The care team reviews an ABG obtained during recovery because the patient briefly required supplemental oxygen earlier.
RR
16/min
16/min
SpO₂
98% RA
98% RA
HR
78/min
78/min
BP
118/72
118/72
Appearance
Calm, no distress
Calm, no distress
Breath Sounds
Clear bilaterally
Clear bilaterally
ABG Results
pH7.40
PaCO₂40
HCO₃24
PaO₂92
Step 1
Determine the pH Status
The pH is 7.40. How should it be classified?
Step 2
Identify the Primary Pattern
Compare the pH with PaCO₂ and HCO₃. Which component explains the pH pattern?
pH 7.40 | PaCO₂ 40 | HCO₃ 24
Step 3
Evaluate Compensation
Is the opposite system trying to compensate for the primary disorder?
pH 7.40 | PaCO₂ 40 | HCO₃ 24 | PaO₂ 92
Step 4
Assess Oxygenation
The PaO₂ is 92 mm Hg. How would you classify oxygenation?
Reference: Severe 0–39 · Moderate 40–59 · Mild 60–79 · Normal 80–100 mm Hg
Step 5
Build the Complete Interpretation
Select the best final ABG interpretation.
Clinical Connection
Final interpretation: Normal ABG with Normal Oxygenation
No acid-base disorder is present.
Ventilation appears normal based on PaCO₂.
Oxygenation is normal on room air.
Possible Clinical Causes
Healthy baseline ABG
Effective ventilation
Adequate gas exchange
Board Pearl
Start with normal values first. A strong sense of normal makes abnormal patterns much easier to recognize.