A spirometry report shows FVC of 3.2 L (predicted 4.5 L), FEV1 of 2.6 L (predicted 3.7 L), FEV1/FVC ratio of 81%, TLC reduced on plethysmography. DLCO is reduced. This pattern is most consistent with:

• A COPD (obstructive pattern with air trapping)
• B Asthma (obstructive pattern reversible with bronchodilator)
• C Respiratory muscle weakness (restrictive pattern with normal DLCO corrected for VA)
• D Interstitial lung disease (restrictive pattern with impaired gas transfer) ✓

Explanation

Reduced FVC, preserved or elevated FEV1/FVC ratio (>70%), and reduced TLC confirm a restrictive pattern. Reduced DLCO indicates impaired alveolar-capillary gas transfer, as seen in interstitial fibrosis where thickened membranes impede diffusion. Respiratory muscle weakness produces restriction but DLCO/VA (corrected for alveolar volume) is typically normal. COPD is obstructive with reduced FEV1/FVC and increased TLC/RV due to air trapping. Asthma shows reversible obstruction.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.