Functional changes during nutritional repletion in patients with lung disease.

In conclusion, the weight loss in COPD is associated with hypermetabolism. Under these circumstances, caloric intake may be insufficient to meet increased metabolic demands, thereby contributing to progressive weight loss. This is in contrast to depleted surgical patients who have energy expenditures 5% below predicted. There is an increased VE in patients receiving a high-carbohydrate diet, secondary to an increased VCO2 that is similar to that seen in patients with neither COPD nor weight loss. Neither diet composition, whether high-carbohydrate or high-fat, nor refeeding have any effect on PaCO2. However, ventilatory drive does appear to be influenced by nutritional repletion. There was an increased sensitivity to PaCO2, independent of diet composition, during a high caloric intake. Respiratory and skeletal muscle function increased, particularly strength, endurance, and work efficiency, indicating that the increased metabolic demand can be well tolerated. It should be noted, however, that refeeding the COPD patient must be done as a preventive measure at the start of weight loss. Patients with long-term weight loss and end-stage COPD appear unable to tolerate any increase in metabolic demand; consequently, they cannot improve respiratory and skeletal muscle function through refeeding.