📈 Station 8 — Interpretation of Spirometry in Asthma/COPD
🎯 Task
You are provided with a spirometry report and a short respiratory clinical scenario. Interpret the spirometry systematically, identify any ventilatory abnormality, and state how the findings relate to asthma or COPD.
⚡ Model Station Answer What to say in the exam
- Pattern: I would first assess the FEV₁/FVC ratio; a reduced ratio indicates an obstructive ventilatory pattern.
- I would then assess the FEV₁ and FVC and compare pre- and post-bronchodilator values where available.
- Asthma: significant improvement after bronchodilator supports variable expiratory airflow limitation.
- COPD: persistent post-bronchodilator airflow obstruction, particularly with a compatible smoking or exposure history, supports COPD.
- Conclusion: I would correlate the spirometry with the supplied symptoms and clinical history before giving the final interpretation.
🔎 Stepwise Procedure / Approach
- Confirm the report. Check patient details, predicted/reference values and whether measurements are pre- or post-bronchodilator.
- Check test quality. Ensure the report indicates acceptable and reproducible spirometry before interpreting the numbers.
- Start with FEV₁/FVC. Compare the ratio with the report’s lower limit of normal. A reduced ratio indicates airflow obstruction.
- Assess FEV₁. Note the measured value and percentage predicted to estimate the degree of reduction in expiratory airflow.
- Assess FVC. Determine whether it is preserved or reduced. A reduced FVC with a preserved ratio may suggest restriction, but spirometry alone does not confirm restrictive lung disease.
- Check bronchodilator response. Compare pre- and post-bronchodilator FEV₁/FVC and FEV₁ or FVC. In adults, an increase in FEV₁ or FVC of ≥12% and ≥200 mL supports significant variable airflow limitation.
- Correlate with the scenario. Variable symptoms with significant reversibility favor asthma; persistent post-bronchodilator obstruction with chronic smoking/exposure history favors COPD.
- State one final interpretation. Give the ventilatory pattern first, followed by the clinical correlation: for example, “obstructive spirometry with significant reversibility, supporting asthma.”
🖼️ Visual Learning
Spirometry Interpretation — Obstruction, Reversibility and Asthma/COPD Correlation
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🎥 Practical Video
A step-by-step OSCE-focused demonstration covering FEV₁, FVC, FEV₁/FVC and recognition of obstructive versus restrictive spirometry patterns.
📝 Important Viva Questions
Q1. What does FEV₁ represent?
FEV₁ is the volume of air forcibly exhaled during the first second of a forced expiration after maximal inspiration.
Q2. What does FVC represent?
FVC is the total volume of air that can be forcibly exhaled after a maximal inspiration.
Q3. What spirometric finding indicates an obstructive ventilatory pattern?
The key finding is a reduced FEV₁/FVC ratio compared with the appropriate lower limit of normal.
Q4. What bronchodilator response supports the diagnosis of asthma in an adult?
An increase from baseline in FEV₁ or FVC of at least 12% and at least 200 mL supports significant variable expiratory airflow limitation.
Q5. What spirometric criterion supports persistent airflow obstruction in COPD?
A post-bronchodilator FEV₁/FVC below 0.70 in the appropriate clinical context supports the diagnosis of COPD.
Q6. Can a restrictive ventilatory defect be confirmed by spirometry alone?
No. A reduced FVC with a preserved or increased FEV₁/FVC may suggest restriction, but confirmation requires measurement of lung volumes, particularly total lung capacity.
Q7. How do you distinguish asthma from COPD when interpreting spirometry?
Look for variable airflow limitation or significant bronchodilator responsiveness supporting asthma versus persistent post-bronchodilator obstruction supporting COPD, and always correlate with the clinical history.