RT Priority
Assess the cause of tachypnea, monitor oxygenation, and avoid assuming anxiety until dangerous causes are considered.
Patient 3
A 34-year-old patient presents to urgent care with sudden shortness of breath, chest tightness, and tingling around the mouth after a stressful event. She is anxious and breathing rapidly.
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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 34-year-old patient presents to urgent care with sudden shortness of breath, chest tightness, and tingling around the mouth after a stressful event. She is anxious and breathing rapidly.
RR
32/min
32/min
SpO₂
97% RA
97% RA
HR
118/min
118/min
BP
132/78
132/78
Appearance
Anxious, speaking quickly
Anxious, speaking quickly
Breath Sounds
Clear bilaterally
Clear bilaterally
ABG Results
pH7.52
PaCO₂28
HCO₃24
PaO₂88
Step 1
Determine the pH Status
The pH is 7.52. 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 7.52 | PaCO₂ 28 | HCO₃ 24
Step 3
Evaluate Compensation
Is the opposite system trying to compensate for the primary disorder?
pH 7.52 | PaCO₂ 28 | HCO₃ 24 | PaO₂ 88
Step 4
Assess Oxygenation
The PaO₂ is 88 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: Uncompensated Respiratory Alkalosis with Normal Oxygenation
The main pattern is excessive ventilation causing low CO₂.
Oxygenation is normal, so the problem is ventilation pattern rather than oxygen transfer.
Clinical context matters: anxiety is one possibility, but always assess for serious causes of tachypnea.
Possible Clinical Causes
Anxiety or panic with hyperventilation
Pain
Fever or sepsis early response
Pulmonary embolism
Excessive ventilator rate
Board Pearl
Respiratory alkalosis means CO₂ is too low. Think hyperventilation.