RT Priority
Support airway and breathing, monitor work of breathing, and recognize that Kussmaul respirations are compensation—not the primary problem.
Patient 4
A 19-year-old patient with type 1 diabetes arrives with abdominal pain, nausea, fruity breath, and deep rapid breathing. Blood glucose is very elevated and dehydration is suspected.
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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 19-year-old patient with type 1 diabetes arrives with abdominal pain, nausea, fruity breath, and deep rapid breathing. Blood glucose is very elevated and dehydration is suspected.
RR
30/min, deep
30/min, deep
SpO₂
99% RA
99% RA
HR
126/min
126/min
BP
96/58
96/58
Appearance
Ill, dry mucous membranes
Ill, dry mucous membranes
Breath Sounds
Clear; Kussmaul pattern
Clear; Kussmaul pattern
ABG Results
pH7.25
PaCO₂28
HCO₃12
PaO₂96
Step 1
Determine the pH Status
The pH is 7.25. 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 7.25 | PaCO₂ 28 | HCO₃ 12
Step 3
Evaluate Compensation
Is the opposite system trying to compensate for the primary disorder?
pH 7.25 | PaCO₂ 28 | HCO₃ 12 | PaO₂ 96
Step 4
Assess Oxygenation
The PaO₂ is 96 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: Partially Compensated Metabolic Acidosis with Normal Oxygenation
The primary issue is metabolic acid buildup or bicarbonate loss.
The patient is compensating by hyperventilating to blow off CO₂.
Oxygenation is normal, even though the patient looks very sick.
Possible Clinical Causes
Diabetic ketoacidosis
Lactic acidosis
Renal failure
Severe diarrhea with bicarbonate loss
Toxin ingestion
Board Pearl
In metabolic acidosis, the lungs compensate by decreasing PaCO₂ through increased ventilation.