Nutritional factors in the pathogenesis and therapy of respiratory insufficiency in neuromuscular diseases.

Malnutrition is a serious threat to patients with neuromuscular disease and marginally-compensated respiratory muscle weakness. It causes atrophy of inspiratory muscles, further weakening them. It reduces respiratory drive, potentially aggravating respiratory failure, either directly or indirectly, by promoting atelectasis and pneumonia, and it contributes strongly to such patients' risk of infection, their most common cause of death. In treating such patients, it must be remembered that abrupt increases in nutritional support, particularly with high percentages of carbohydrates, will increase CO2 production, potentially worsening ventilatory failure. Certain selected neuromuscular disease patients benefit from specific nutritional treatments (carnitine for carnitine deficient patients, high-calorie diets for muscular dystrophy and acid-maltase deficiency). Finally, the amino acid, fat, and nucleic acid content of the diet affects the immune response in beneficial or harmful ways, that are just now being elucidate. The potential for useful nutritional interventions in patients with neuromuscular diseases has never looked better, but is not yet fully realized. The challenges for the future will be to work out the beneficial and harmful effects of the various nutrients in the various diseases, to find ways to rapidly identify patients who will benefit, and to determine the safest, least uncomfortable, and most effective methods of delivery of the required nutrients.