The impact of undernutrition on lung physiology and respiratory muscle performance is still incompletely investigated. The purpose of this study was to assess the functional consequences of malnutrition on the respiratory system in stable patients with anorexia nervosa (AN).
Pulmonary function tests, maximal inspiratory pressure (Pimax), maximal expiratory pressure (Pemax), and the parameters of control of breathing were obtained in 27 patients with AN (mean [± SD] age, 24 ± 7 years; BMI, 16 ± 1 kg/m2; duration of disease, 6 ± 6 years) and in a group of matched healthy subjects.
Compared with control subjects, significant reductions in the diffusing capacity of the lung for carbon monoxide (Dlco) and lung diffusion capacity corrected for alveolar ventilation (p < 0.001), which progressively worsened with the duration of disease, were found in the AN group. Only the membrane diffusing capacity was reduced in patients with AN (p < 0.05), while pulmonary capillary blood volume was similar to that of control subjects. Lung density measurements based on CT scan analysis were normal in a subgroup of eight patients with AN with low Dlco. Both Pimax and Pemax were decreased in patients with AN (p < 0.001), but the mild-to-moderate impairment to generate force of the respiratory muscles did not progress with time. In these patients with AN, the parameters of control of breathing were in the normal range and were comparable to those of control subjects.
The functional alterations found in patients with AN indicate the presence of the progressive enlargement of peripheral lung units without relevant alveolar septa destruction. In the first 3 years of disease, appreciable weakness of respiratory muscles develops in patients with stable AN without further impairment over time.