Can Restrictive Lung Disease and Hyperinflation Coexist?
Yes, a patient can have both restrictive lung disease and hyperinflation simultaneously, though this represents a complex mixed pattern that requires careful interpretation and measurement of total lung capacity (TLC) to properly characterize the underlying pathophysiology. 1
Understanding the Paradoxical Coexistence
True Mixed Disease vs. Pseudo-Restriction
The coexistence of restriction and hyperinflation occurs through two distinct mechanisms:
True mixed obstruction-restriction is confirmed when TLC is reduced below the 5th percentile AND there is evidence of air trapping with elevated residual volume (RV) or RV/TLC ratio, indicating both processes are genuinely present 1, 2
Pseudo-restrictive pattern occurs more commonly when severe airflow obstruction causes gas trapping that prevents complete exhalation, artificially lowering FVC on spirometry while TLC remains normal or elevated—this mimics restriction but is actually pure obstruction 1, 2
Clinical Scenarios Where Both Truly Coexist
Combined pulmonary fibrosis and emphysema (CPFE) represents the classic example where both pathologies genuinely coexist:
Heavy smokers can develop emphysema in upper lobes (causing hyperinflation) while simultaneously developing interstitial fibrosis in lower lobes (causing restriction) 3
These patients paradoxically show normal or near-normal lung volumes because the hyperinflation from emphysema masks the volume loss from fibrosis 3
Despite preserved volumes, these patients demonstrate severe gas exchange impairment, poor exercise tolerance, and often develop severe pulmonary hypertension 3
The relatively preserved lung volumes dangerously underestimate disease severity and can delay appropriate diagnosis 3
Essential Diagnostic Algorithm
Step 1: Measure TLC Immediately
TLC measurement by body plethysmography is mandatory to differentiate true mixed disease from obstruction with gas trapping 1, 4
If TLC is normal or elevated: the primary problem is obstructive disease with hyperinflation, not true restriction 1
If TLC is reduced below 5th percentile: true restrictive component is present, but check RV/TLC ratio to assess for concurrent air trapping 2, 1
Step 2: Assess Gas Trapping
Elevated RV or RV/TLC ratio above upper limits indicates air trapping and hyperinflation, even when TLC is reduced 2
In severe obstruction, FRC, RV, TLC and RV/TLC all tend to increase due to decreased lung elastic recoil and dynamic mechanisms 2
Step 3: Obtain High-Resolution CT
HRCT is essential to identify the structural basis for mixed patterns, including emphysema distribution, fibrotic changes, and their anatomic relationship 5, 2
Look specifically for upper lobe emphysema with lower lobe fibrosis in smokers, which characterizes CPFE syndrome 3
Step 4: Measure DLCO
Reduced DLCO helps differentiate parenchymal causes and predicts mortality in both restriction and obstruction 4, 5
Severely reduced DLCO despite preserved volumes strongly suggests CPFE 3
Critical Pitfalls to Avoid
Never diagnose restriction based on reduced FVC alone without measuring TLC, as this pattern frequently represents submaximal effort, early airway closure, or gas trapping rather than true restriction 2, 1, 4
Do not assume normal lung volumes exclude serious disease in patients with dyspnea and smoking history—CPFE can present with deceptively normal spirometry and volumes despite severe functional impairment 3
Recognize that hyperinflation in restrictive disease worsens outcomes by increasing elastic load on inspiratory muscles, contributing to dyspnea, and putting muscles at mechanical disadvantage 2
Clinical Implications
For Obstructive Disease with Hyperinflation
Hyperinflation measured as inspiratory capacity (IC)/TLC is an independent predictor of respiratory and all-cause mortality in COPD 2
Dynamic hyperinflation increases with exercise, increasing mechanical load while reducing inspiratory muscle advantage 6, 7
Bronchodilator therapy remains the cornerstone even with mild obstruction, as symptomatic improvement often results from reducing hyperinflation 1, 6
For True Mixed Disease
Treatment must target both components: bronchodilators for obstruction and disease-specific therapy for the restrictive component 1
In CPFE, the combination portends worse prognosis than either disease alone, with high risk of pulmonary hypertension and mortality 3
Lung transplant evaluation should be considered early in appropriate candidates with CPFE given the aggressive natural history 3