NETT Criteria for Lung Volume Reduction Surgery
The NETT eligibility criteria for surgical lung volume reduction include: FEV1 ≤45% predicted, TLC ≥100% predicted, RV ≥150% predicted, room air PaCO2 ≤60 mmHg, and PaO2 ≥45 mmHg, with patients having upper-lobe predominant emphysema and low exercise capacity showing the greatest survival benefit 1.
Key Inclusion Criteria
The National Emphysema Treatment Trial established specific physiological parameters for LVRS candidacy 1:
- Spirometry: FEV1 ≤45% predicted
- Lung volumes: TLC ≥100% predicted and RV ≥150% predicted
- Gas exchange: Room air resting PaCO2 ≤60 mmHg and PaO2 ≥45 mmHg
- Emphysema distribution: Heterogeneous pattern, particularly upper-lobe predominant disease
Critical Exclusion Criteria (High-Risk Group)
Patients with FEV1 ≤20% predicted AND either DLCO ≤20% predicted OR homogeneous emphysema on HRCT are at significantly increased risk of mortality following LVRS and should not undergo this procedure 2. This high-risk subgroup demonstrated higher mortality than medical management in the original NETT trial 2.
Optimal Candidate Profile
The strongest evidence for survival benefit comes from patients with 2, 3:
- Upper-lobe predominant emphysema (confirmed on CT and perfusion scan)
- Low postrehabilitation exercise capacity
This specific subgroup showed improved 5-year survival compared to medical management. Patients with high exercise capacity showed improvements in health status and exercise capacity but no survival advantage 2.
Important Clinical Nuances
Emphysema distribution pattern is the most critical selection factor 4. Upper lobe heterogeneous emphysema on chest CT and lung perfusion scan strongly predicts better outcomes, with mean FEV1 improvement of 73.2% versus only 37.9% for lower lobe or diffuse patterns 4.
Common Pitfalls to Avoid
- Do not rely solely on FEV1 or DLCO cutoffs without considering emphysema distribution pattern
- Homogeneous emphysema is a contraindication even if other parameters are acceptable
- The presence of hypercapnia >60 mmHg excludes candidacy 4
Emerging Evidence on Expanded Criteria
Recent data suggests that carefully selected "beyond-criteria" patients (those meeting 2+ expanded criteria including age ≥75, BMI <18.5, sPAP >35 mmHg, or prior thoracic interventions) may have comparable outcomes to standard-criteria patients when evaluated by experienced multidisciplinary teams 5. However, the original NETT high-risk criteria (FEV1 ≤20% with DLCO ≤20% or homogeneous disease) remain absolute contraindications 6.