Purpose: We hypothesized that long-term protein-calorie malnutrition in humans results in emphysematous changes in the lung parenchyma.
Methods and Materials: CT scans were obtained from 14 subjects with a DSM IV diagnosis of anorexia nervosa (AN). All patients gave their informed consent to take part in this study. Clinical data: sex, age, smoking history, body mass index (BMI), total body fat, hemoglobin (HGB), history of age of onset of AN and duration of malnutrition, and history of respiratory disease were recorded. Pulmonary function data (static and dynamic lung volumes, diffusing capacity and respiratory muscle strength) were measured. CT scans were obtained from three regions of the lung (at the level of the aortic arch, the carina, and the posterior position of the 8th rib) using a Multi-Slice CT scanner (GE Lightspeed Ultra). Images were reconstructed using 1.25, 2.5 and 5 mm CT slice thickness. The mean lung density (g/ml), lung inflation (ml gas/g tissue), and surface area to volume ratio (S/V) were measured using the x-ray attenuation values of the CT images. The CT measures were correlated with the anthropometric and the pulmonary function data measurements and compared to the same data in 16 control subjects.
Results: These data show the AN subjects were not anemic (HGB=12.6±0.9 g/dL) and there were no significant differences in age or pulmonary function between AN and control subjects. There was a significant difference in the mean lung density (0.18±0.04 g/ml vs 0.23±0.03 g/ml, p=0.001), mean lung inflation (5.0±1.5 ml/g vs 3.7±0.7 ml/g, p=0.006) and S/V (13.6±7.0 m2/ml vs 25.1±6.9 m2/ml, p=0.0001) between AN and control subjects. Simple regression analysis showed there was no significant correlation between FEV1, FVC, TLC and maximum expiratory pressure and CT measurements. However, there was a significant correlation between the percent predicted diffusing capacity of the lung for carbon monoxide (DLCO%p, corrected for hemoglobin) and mean lung density (r=0.75) mean lung inflation (r=0.81), S/V (r=0.67) and BMI (r=0.70) (p£0.05) in the AN subjects. A step-wise multiple regression showed the best predictor of DLCO%p was mean lung inflation, S/V and the percentage of lung less 6 ml/g of air (R2=0.86, p=0.01).
Conclusion: There is a significant correlation between the diffusing capacity of the lung and CT measurements of lung structure and body mass index in patients with AN. These data suggest that there are "emphysema-like" changes (density, inflation, S/V) in the underlying structure of the lung in malnourished patients. (J.M. received a grant from GE Medical Systems, Canada.)
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