The effects of lung volume reduction treatment on diffusing capacity and gas exchange.

Lung volume reduction (LVR) treatment in patients with severe emphysema has been shown to have a positive effect on hyperinflation, expiratory flow, exercise capacity and quality of life. However, the effects on diffusing capacity of the lungs and gas exchange are less clear. In this review, the possible mechanisms by which LVR treatment can affect diffusing capacity of the lung for carbon monoxide (D LCO) and arterial gas parameters are discussed, the use of D LCO in LVR treatment is evaluated and other diagnostic techniques reflecting diffusing capacity and regional ventilation (V')/perfusion (Q') mismatch are considered.A systematic review of the literature was performed for studies reporting on D LCO and arterial blood gas parameters before and after LVR surgery or endoscopic LVR with endobronchial valves (EBV). D LCO after these LVR treatments improved (40 studies, n=1855) and the mean absolute change from baseline in % predicted D LCO was +5.7% (range -4.6% to +29%), with no real change in blood gas parameters. Improvement in V' inhomogeneity and V'/Q' mismatch are plausible explanations for the improvement in D LCO after LVR treatment.