Potential effects of nutritional state on pulmonary function in cystic fibrosis

There are a number of observations which suggest that malnutrition and decreasing pulmonary function are parallel phenomena in chronic lung disease. Causality for either has not been established. A potential link between the two may be the diminishing function of respiratory muscles which accompanies weight loss. Data from adult patients with chronic obstructive lung disease are presented which suggest that respiratory muscle fibers progressively atrophy, not hypertrophy, in the face of increasing airway obstruction. This lack of compensation is probably nonspecific since nonrespiratory muscles demonstrate the same trend. This observation may explain some of the impaired respiratory muscle function which has been documented in patients with chronic lung disease. There are no morphologic data available for older patients with cystic fibrosis, but the processes which impair muscle function may prove to be similar in both groups of patients. The effect of malnutrition on respiratory muscle fiber size remains to be determined.