Our data support the hypothesis that improved oxygen delivery is important for weight gain in patients with emphysema. We found that there was no correlation between weight gained after LVRS and improvement in pulmonary mechanics. However, an increased Dlco did correlate with weight gain. Patients who gained weight could have increased Dlco simply from increases in hemoglobin as a result of improved nutrition. This does not appear to be the case because there was slight fall in hemoglobin (14.1 ± 0.2 to 13.7 ± 0.2 g/dL), with 57% of patients having a lower hemoglobin level 1 year post-LVRS. The fall in hemoglobin could reflect improved oxygenation in some of these patients. In addition, there was no correlation between changes in hemoglobin and changes in body weight (data not shown). We speculate that improvement in Dlco may be a result of opening of pulmonary vessels compressed by hyperinflated lung. This increase in available pulmonary capillary bed could result in an enhanced ability to augment cardiac output during exercise. Improvements in oxygen delivery would decrease tissue oxygen debt and allow for increased lean body mass. However, in our study, the Dl/Va did not change after surgery (data not shown), which would argue that the improvement in Dlco is not a result of simple capillary recruitment. Consequently, proving or refuting this notion awaits a more formal assessment of changes in oxygen delivery (both at rest and during exercise) and weight change after LVRS. canadian neighbor pharmacy
Our data demonstrate that weight gains 1 year after LVRS were greater in women than men. There are relatively few studies that compare the metabolic response to severe COPD in men and women. In a cross-sectional analysis of exercise testing at specific levels of airway obstruction, Carter et al found that men demonstrated progressive reductions in body weight and maximal oxygen uptake, oxygen pulse, and maximum exercise ventilation, even with mild airway obstruction. Women maintained these variables until the disease reached moderate or severe levels. Carter et al also estimated that cardiac output at peak exercise was maintained in women with mild disease. These data and those from the present study suggest that the physiologic response to airway obstruction may be different in men and women. This could be due to hormonal differences or differences in resting energy expenditure, perhaps as a result of sex-specific respiratory muscle recruitment. Because very few studies to date have compared the physiologic responses in men and women with emphysema, our data emphasizes the need to consider sex as a variable for future studies examining the metabolic consequences of severe airway obstruction.