What is the interpretation of spirometry findings showing a Forced Expiratory Volume (FEV1) to Forced Vital Capacity (FVC) ratio of 81% post-Ventolin (albuterol), with an FVC of 67% and FEV1 of 69%, and a Peak Expiratory Flow (PEF) of 76%?

Spirometry Interpretation: Restrictive Pattern with Normal Post-Bronchodilator FEV1/FVC Ratio

These spirometry findings demonstrate a restrictive ventilatory pattern characterized by proportionally reduced lung volumes (FVC 67%, FEV1 69%) with a preserved post-bronchodilator FEV1/FVC ratio of 81%, which rules out obstructive airway disease. 1

Primary Pattern Analysis

The FEV1/FVC ratio of 81% is above the threshold for obstruction and indicates normal airway caliber relative to lung volume. 1

• The post-bronchodilator FEV1/FVC ratio of 81% exceeds the 70% threshold used to define obstruction and is well above the lower limit of normal for most age groups 1
• Both FEV1 (69% predicted) and FVC (67% predicted) are proportionally reduced, falling below 80% predicted 1
• The PEF of 76% is also reduced but less severely than the volume parameters 1

Restrictive vs. Poor Effort Pattern

This pattern most likely represents either true restriction or submaximal effort, which cannot be definitively distinguished without lung volume measurements. 1

Key Diagnostic Consideration:

• 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 1
• A reduced FVC with normal FEV1/FVC ratio suggests restriction only when confirmed by TLC measurement below the 5th percentile of predicted 1
• A reduced VC by itself does not prove a restrictive ventilatory defect—it is associated with a low TLC no more than half the time 1

Alternative Explanations:

• Patchy collapse of small airways early in exhalation can produce this pattern with normal TLC but increased RV 1
• Slow flow preventing complete exhalation to residual volume 1
• Submaximal inspiratory or expiratory efforts during testing 1

Clinical Significance and Symptom Burden

Despite being classified as "mild" by spirometric criteria, patients with this restrictive pattern report significant respiratory symptoms and impaired quality of life comparable to COPD patients. 2

• Patients with spirometrically-defined restrictive defects (FEV1/FVC >0.70, FVC <80%) report more phlegm, dyspnea, and wheezing than healthy controls 2
• Quality of life scores are similar to those with obstructive patterns compatible with COPD 2
• The population prevalence of this pattern is approximately 12.7% with significant geographical variation 2

Bronchodilator Response Assessment

The post-bronchodilator values indicate no significant reversible airflow obstruction, as the FEV1/FVC ratio remains normal after albuterol administration. 1, 3

• Post-bronchodilator testing is essential to confirm the absence of reversible obstruction 1
• The preserved ratio after bronchodilator rules out asthma and COPD as primary diagnoses 4
• Maximum bronchodilator effect typically occurs at 1 hour post-administration with effects lasting 3-6 hours 3

Recommended Next Steps

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. 1

Diagnostic Algorithm:

1. Obtain lung volume measurements (TLC, RV, RV/TLC ratio) 1

   • TLC <5th percentile confirms true restrictive defect 1
   • Normal TLC with increased RV suggests peripheral airway dysfunction 1
   • Normal TLC with normal RV suggests poor effort or technique 1

2. Review flow-volume curve morphology 1

   • Convex pattern supports restriction 1
   • Concave pattern at end of maneuver suggests incomplete exhalation 1

3. Consider measurement of slow vital capacity (inspiratory or expiratory) 1

   • May provide more accurate FEV1/VC ratio if peripheral airway collapse is present 1

4. Assess for underlying causes if true restriction confirmed 1

   • Interstitial lung disease
   • Chest wall disorders
   • Neuromuscular disease
   • Obesity (high BMI is independently associated with restrictive pattern) 2

Common Pitfalls to Avoid

• Do not diagnose restriction based on spirometry alone without TLC measurement 1
• Do not use single-breath TLC estimates (such as VA from DLCO testing) to confirm restriction, as these systematically underestimate TLC 1
• Do not dismiss this pattern as clinically insignificant—patients experience substantial symptom burden 2
• Ensure adequate coaching and effort during testing, as poor technique is the most common cause of this pattern 1