A comparison of single breath and re-breathe diffusing capacity in emphysema patients and controls.

In emphysema patients, gas dilutional alveolar volume is underestimated by a 10s single breath maneuver at total lung capacity (TLC) compared with re-breathing at functional residual capacity (FRC); corresponding underestimation of single breath diffusing capacity (DLCO) in emphysema has not been demonstrated. The purpose of this study was to quantify the degree to which re-breathe DLCO at FRC (DLCO(RB)) differs from single breath DLCO at TLC (DLCO(SB)) in emphysema. In 37 consecutively recruited patients with moderate to severe emphysema (FEV1/FVC 40%±10% predicted), DLCO(RB) as % predicted of 91 controls without cardiopulmonary disease was 79%±24%, significantly greater than % predicted DLCO(SB) (44%±19%; p<0.

Quantification of single-breath underestimation of lung volume in emphysema.

The extent to which a single breath measurement represents available gas dilutional as well as compressible thoracic volume in emphysema patients has not been quantified. We therefore measured single breath (TLCSB) and rebreathe helium dilution (TLCRB), and plethysmographic lung volume (TLCpleth), in fifty-five outpatients with clinical and radiographic emphysema, and in twenty-one normal controls. Among emphysema patients, TLCSB increasingly underestimated both TLCpleth and TLCRB as FEV1% predicted decreased (p for interaction=0.