Recent studies have demonstrated the importance of nutrition in the care of patients with respiratory disease, particularly those with chronic obstructive pulmonary disease. They make clear the detrimental changes which occur in malnutrition but emphasize that overenthusiastic refeeding can also be harmful. These two opposing considerations indicate the need to accurately determine the interaction between metabolism, ventilation and the effects of nutrients. This interaction involves a number of different factors, including the effects of nutrient administration on whole body metabolism, respiratory muscle function, skeletal muscle function, lung function and central control of ventilation. The preexisting nutritional state and clinical condition also affect the responses that will be obtained. The complexity of this interaction indicates that data from animal models cannot be directly extrapolated to human illness. If these relationships are to be properly understood, the processes involved must be specifically examined in different clinical conditions. This application intends to combine measurements of whole body metabolic changes with measures of ventilatory function to establish the efficacy of varying quantify and composition of nutritional support in different clinical conditions. The use of a non-invasive canopy system will allow simultaneous measurements of gas exchange and breathing pattern without the use of a mouthpiece, facemask and nose clip. Concurrent measurements of diaphragmatic and lung function will allow a determination to be made of whether the observed alterations in breathing pattern represent a primary change in the control of breathing or are due to improved diaphragmatic and pulmonary function. Low-level supine exercise will be employed to determine whether decreases in ventilatory reserve not apparent in studies of resting breathing have occurred. Measurements of nitrogen, potassium, and sodium and water balance will allow an understanding of whether malnourished patients with respiratory disease respond to nutritional support in a manner comparable to patients with an equivalent degree of malnutrition but without respiratory disease. Studies in normal volunteers given different nutrients intakes along with infusions of the 'stress' hormones will help elucidate the factors which mediate the alterations in ventilation occurring in patients with acute respiratory failure following trauma.