Nutrition and the respiratory system
Malnutrition and weight loss are among the signs of a poor prognosis in the natural history of patients with COLD.123, 124 Patients whose only source of daily nutrition is 2–31 of 5% dextrose suffer malnutrition and weight loss. This has been documented to be detrimental.SUMMARY
Currently, there are insufficient data to propose the optimum form and amount of nutritional intake. Thus, it is appropriate to suggest moderation in nutritional support of patients with compromised pulmonary reserve. Glucose infusions may be expected to replenish tissue glycogen and, hence, be associated with improved work performance; however, CO2 production is significantly increased. However, an increased RQ may provide a more favorable alveolar Po2 which could be important in patients with COLD during room air breathing. Fat emulsions are commercially available, can minimize CO2 production, and have been shown to be N sparing. However, serum hyperlipemia may compromise pulmonary diffusing capacity. Increasing nitrogen intake can increase ventilatory drive, but this may lead to a feeling of dyspnea and be detrimental in patients unable to increase minute ventilation.SUMMARY
Parenteral nutrition should be guided by whether the goal is to: (a) preserve lean body mass in patients who are in satisfactory nutritional condition but whose return to oral intake is not imminent, or (b) restore lean body mass in patients who have lost greater than 10% of normal body weight. In patients where the intent is maintenance of lean body mass, nutritional support should be designed to attain calorie and nitrogen equilibrium. Practically speaking, this means: (1) energy intake of 1–1.2 χ energy expenditure; (2) nitrogen intake of 200–300 mg/kg. At this institution, 50% of the nonprotein calories are given as fat emulsions. In patients where the goal is restoration of lean body tissue, the nutritional regimen should be designed to achieve a distinctively positive calorie and nitrogen balance. Energy intake is set at 1.4–1.6 χ energy expenditure. Nitrogen intake is between 250–400 mg/kg body weight. One-half of the nonprotein calories are given as lipid.SUMMARY
These recommendations are based upon limited data and indirect evidence. Further studies of nutrition and respiration are needed to construct more definitive guidelines in this important area of clinical care.