A woman with resolved alveolitis, normal CT, hyperinflated lung volumes, near‑normal diffusing capacity, and spirometry showing FEV1 53% predicted and FVC 85% predicted—what is the likely obstructive diagnosis and what management steps are recommended?

Obstructive Lung Disease with Air-Trapping

This patient has obstructive lung disease, most likely COPD or asthma with air-trapping, not a restrictive defect. The spirometry shows FEV1 53% predicted and FVC 85% predicted, yielding an FEV1/FVC ratio of approximately 62%, which is below the 5th percentile and diagnostic of obstruction. 1

Why This Is Obstruction, Not Restriction

• The FEV1/FVC ratio < 70% (approximately 62% in this case) definitively establishes airflow obstruction according to European Respiratory Society criteria. 1

• The reduced FVC (85% predicted) does NOT indicate restriction—it reflects incomplete exhalation due to early airway closure and gas-trapping, a hallmark of obstructive disease. 1, 2

• The hyperinflated lung volumes on examination confirm air-trapping, which is characteristic of obstruction (emphysema or severe asthma), not restriction. 1

• True restriction requires TLC < 5th percentile measured by body plethysmography; spirometry alone cannot diagnose restriction, and a reduced FVC with low FEV1/FVC almost always represents obstruction with gas-trapping. 1, 3

Critical Diagnostic Steps

1. Confirm the Obstructive Pattern

• Measure total lung capacity (TLC), residual volume (RV), and RV/TLC ratio by body plethysmography to document hyperinflation and exclude coexisting restriction. 1, 3

• Expected findings: TLC normal or elevated, RV and RV/TLC elevated (>5th percentile), confirming pure obstruction with air-trapping. 1, 2

• If TLC is also reduced (< 5th percentile), this would indicate a rare mixed obstructive-restrictive defect (e.g., combined pulmonary fibrosis and emphysema), but the hyperinflated volumes and normal CT make this unlikely. 1, 4

2. Assess Reversibility

• Perform post-bronchodilator spirometry to determine if the obstruction is reversible (asthma) or fixed (COPD). 1, 5, 6

• Reversibility is defined as an increase in FEV1 or FVC ≥ 12% AND ≥ 200 mL after inhaled short-acting bronchodilator (e.g., albuterol 400 mcg). 1, 5, 6

• Significant reversibility suggests asthma; lack of reversibility points to COPD, though many COPD patients show partial bronchodilator response. 1, 2

3. Measure Diffusing Capacity (DLCO)

• DLCO and transfer coefficient (KCO) help differentiate emphysema from chronic bronchitis or asthma. 1

• Reduced DLCO and KCO indicate emphysema; normal or elevated KCO suggests chronic bronchitis or asthma without parenchymal destruction. 1

• Near-normal diffusing capacity in this patient argues against significant emphysema despite hyperinflation, raising the possibility of asthma or chronic bronchitis. 1

Most Likely Diagnosis

Given the resolved alveolitis, normal CT, hyperinflation, near-normal DLCO, and moderate obstruction (FEV1 53%), the most likely diagnosis is:

• Asthma with chronic air-trapping, especially if bronchodilator reversibility is present. 1, 2

• Chronic bronchitis (COPD phenotype) if reversibility is absent and there is a significant smoking history. 1

• Post-inflammatory airway remodeling from the prior alveolitis, leading to fixed or partially reversible obstruction. 2

Management Algorithm

Step 1: Initiate Bronchodilator Therapy

• Start a long-acting muscarinic antagonist (LAMA) such as tiotropium 5 mcg once daily via inhaler as first-line therapy for symptomatic COPD or persistent asthma. 7

• Add a long-acting beta-agonist (LABA) such as olodaterol 5 mcg once daily if symptoms persist; combination LAMA/LABA (e.g., tiotropium/olodaterol) provides superior bronchodilation and symptom relief compared to monotherapy. 7

• For patients with asthma features (variability, atopy, eosinophilia), add inhaled corticosteroids (ICS) in combination with LABA. 1

Step 2: Assess Response at 4–12 Weeks

• Repeat spirometry and assess symptom improvement (dyspnea, exercise tolerance, rescue inhaler use). 7, 5

• Significant improvement in FEV1 (≥ 12% and ≥ 200 mL) or symptoms confirms asthma or COPD with reversible component; continue and optimize bronchodilator therapy. 1, 5

• Lack of improvement suggests fixed obstruction (COPD); continue LAMA/LABA and consider pulmonary rehabilitation. 1, 7

Step 3: Monitor for Exacerbations and Progression

• Annual spirometry to track FEV1 decline and adjust therapy. 1, 5

• Smoking cessation is mandatory if the patient smokes; it is the only intervention proven to slow FEV1 decline in COPD. 1

• Vaccinations (influenza, pneumococcal, COVID-19) to reduce exacerbation risk. 1

Common Pitfalls to Avoid

• Do not diagnose restriction based on reduced FVC alone—this is the most common error in spirometry interpretation. A reduced FVC with low FEV1/FVC almost always reflects obstruction with air-trapping, not restriction. 1, 3, 8

• Do not assume normal CT excludes significant airway disease—small airway obstruction and air-trapping can occur without visible parenchymal abnormalities on CT. 2

• Do not withhold bronchodilators in "mild" obstruction (FEV1 > 50%)—symptomatic patients benefit from LAMA/LABA therapy regardless of FEV1, and early treatment may prevent progression. 7

• Do not rely on peak expiratory flow (PEF) in advanced obstruction—PEF may be only moderately reduced even when FEV1 is severely impaired, leading to underestimation of disease severity. 1

• Do not overlook poor effort as a cause of proportionally reduced FEV1 and FVC—review the flow-volume loop for reproducibility and adequate effort before concluding obstruction. 1