Analysis of body water compartments in relation to tissue depletion in clinically stable patients with chronic obstructive pulmonary disease

Tissue depletion often occurs in patients with chronic obstructive pulmonary disease (COPD), even in those that are weight-stable. Limited data are available, however, about changes in body water compartments in chronic wasting diseases such as COPD. The purpose of this study was to measure body composition in severe COPD patients with special attention to fat-free mass (FFM) depletion and the distribution of body water compartments. Total body water (TBW) and extracellular water (ECW) were measured by deuterium and sodium bromide dilution techniques, respectively, in 38 COPD patients (age: 65 +/- 9 y, forced expiratory volume in 1 s: 38 +/- 14% of predicted) in a stable clinical condition. FFM was calculated by assuming a hydration coefficient of 73%. Underweight patients [body mass index (BMI; in kg/m2) < or = 21] were characterized by a significantly lower percentage fat mass than normal-weight patients, but no significant difference was found in the ratio of ECW to intracellular water (ICW)(BMI < or = 21: 0.72 +/- 0.12, BMI > 21: 0.71 +/- 0.16; NS). When the study population was divided into depleted patients (FFM/height2 < or = 15 kg/m2) and nondepleted patients (FFM/height2 > 15 kg/m2), there was no significant difference in the percentage fat mass, but the ECW-ICW ratio was significantly higher in the depleted patients (0.78 +/- 0.16) than in the nondepleted patients (0.66 +/- 0.12, P < 0.05); this was most pronounced in women. In conclusion, it was found that COPD patients with extreme FFM wasting are characterized by an increased ECW-ICW ratio despite a relatively spared fat mass.