TABLE 4.

COMPARISON OF INVESTIGATIONAL LUNG VOLUME REDUCTION TECHNIQUES

Technique	Mechanism	PRCT Data	Procedure Type	Procedure Reversible?	Affected by Collateral Ventilation
One-way endobronchial valves (EBVs) implanted in airway	Promotes regional atelectasis by blocking inspiration but allowing expiration	After EBV, mean FEV1 increased 6.8% (60 ml) and mean 6MWD increased 2.55 (9.3 m) compared with control	Bronchoscopy	Yes	Yes
Self-activating coils placed in airway	Atelectasis induced by assuming preformed coiled shape: bends airway and collapses surrounding lung tissue	No	Bronchoscopy	Yes	No
Targeted destruction of emphysematous tissue	BioLVR: Regional instillation of biological agents that collapse and remodel emphysematous regionsBTVA heats and destroys targeted emphysematous tissue	No	Bronchoscopy	No	No
Bypass tract airway stenting	Endobronchial stents placed into emphysematous tissue to enhance deflation	Pending	Bronchoscopy	Yes	No
Transpleural ventilation	Modified tubes placed externally into emphysematous tissue to enhance external deflation	No	Minithoracotomy	Yes	No

Definition of abbreviations: 6MWD = 6-minute-walk distance; BTVA = bronchoscopic thermal vapor ablation; BioLVR = Biological lung volume reduction; PRCT = prospective randomized controlled trial.