Spirometry Interpretation of Restrictive Patterns

Primary Pattern Analysis

The European Respiratory Society suggests that a post-bronchodilator FEV1/FVC ratio of 81% is above the threshold for obstruction and indicates normal airway caliber relative to lung volume 1, 3
A post-bronchodilator FEV1/FVC ratio exceeding 70% is used to define non-obstruction, with the given ratio of 81% being well above the lower limit of normal for most age groups 1, 3
Both FEV1 (69% predicted) and FVC (67% predicted) are proportionally reduced, falling below 80% predicted, indicating a restrictive pattern 1, 2
The PEF of 76% is also reduced but less severely than the volume parameters, suggesting some degree of airway involvement or poor effort 1

The European Respiratory Society indicates that this pattern most likely represents either true restriction or submaximal effort, which cannot be definitively distinguished without lung volume measurements 1, 2, 4
When FEV1 and FVC are concomitantly decreased with a normal or elevated FEV1/FVC ratio, this pattern most frequently reflects failure to inhale or exhale completely, as suggested by the European Respiratory Society 1, 2, 5
A reduced FVC with normal FEV1/FVC ratio suggests restriction only when confirmed by TLC measurement below the 5th percentile of predicted, according to the European Respiratory Society 2, 4

Measurement of total lung capacity (TLC) by body plethysmography is mandatory to confirm true restriction and distinguish it from poor effort or peripheral airway dysfunction, as recommended by the European Respiratory Society 2, 4, 3
Obtaining lung volume measurements (TLC, RV, RV/TLC ratio) helps in confirming true restrictive defect if TLC is <5th percentile, or suggests peripheral airway dysfunction if TLC is normal with increased RV, or poor effort if TLC and RV are normal 2, 4, 3

The European Respiratory Society advises against diagnosing restriction based on spirometry alone without TLC measurement, as this can lead to misdiagnosis 2, 4, 3
It is also recommended not to use single-breath TLC estimates to confirm restriction, as these systematically underestimate TLC, according to the European Respiratory Society 2, 4
Ensuring adequate coaching and effort during testing is crucial, as poor technique is the most common cause of this pattern, as emphasized by the European Respiratory Society 1, 2, 5