Nutrition is an important aspect of patient care in acute or chronic critical illness. Appropriate nutritional support during the acute phase of critical illness has the potential to reverse or mitigate adverse consequences of poor nutritional status. The nutritional status of a chronically critically ill patient depends in part on the nutritional therapy given during acute critical illness. Nutrition in chronic critical illness is essential to ensure the restoration of muscle strength and immune status, both of which are necessary to attain optimal patient function and survival.

This issue of Clinics in Chest Medicine centers on the chronically critically ill patient. This article discusses nutritional support in chronic critical illness by using patients with respiratory failure as a model of critically ill patients. Clearly, clinical examples could focus on patients with renal or hepatic failure, but much data exist documenting the adverse effects of poor nutritional status on thoracopulmonary function.<sup>2 Arora N.S., Rochester D.F. Effect of body weight and muscularity on human diaphragm muscle mass, thickness and area J Appl Physiol 1982 ;  52 : 64-70

Haga clic aquí para ir a la sección de Referencias, 50 Kelsen S.G., Ference M., Kapoor S. Effects of prolonged undernutrition on structure and function of the diaphragm J Appl Physiol 1985 ;  58 : 1354-1359

Haga clic aquí para ir a la sección de Referencias, 84 Thurlbeck W.M. Diaphragm and body weight in emphysema Thorax 1978 ;  33 : 483-487  [cross-ref]

Haga clic aquí para ir a la sección de Referencias</sup> In addition, and probably more importantly, a frequent cause of chronic critical illness and admission to special respiratory or long-term care units is ventilator-dependent chronic respiratory failure.<sup>17 Carson S.S., Bach P.B., Brzozowski L. , y al. Outcomes after long-term care Am J Respir Crit Care Med 1999 ;  159 : 1568-1573

Haga clic aquí para ir a la sección de Referencias, 28 Dasgupta A., Rice R., Mascha E. , y al. Four-year experience with a unit for long-term ventilation (respiratory special care unit) at the Cleveland Clinic foundation Chest 1999 ;  116 : 447-455  [cross-ref]

Haga clic aquí para ir a la sección de Referencias, 41 Gracey D.R., Naessens J.M., Viggiano R.W. , y al. Outcome of patients cared for in a ventilator-dependent in a general hospital Chest 1999 ;  107 : 494-499

Haga clic aquí para ir a la sección de Referencias</sup>

Acute and chronic respiratory failure can be classified nutritionally on the basis of nutritional status and metabolic pathways. Each of these categories defines a specific and characteristic metabolic alteration in which nutritional goals and support differ. Nutritional status is defined as the presence or absence of malnutrition, and hypermetabolism as the degree of metabolic activity in a disease state. Clinical examples of this nutritional classification of respiratory failure include patients with severe chronic obstructive pulmonary disease (COPD), representing a malnourished, nonhypermetabolic patient and patients with septic acute respiratory distress syndrome (ARDS) representing a generally well-nourished but extremely hypermetabolic patient. This article discusses nutritional pathophysiology, goals, and support in these two general but diverse types of patients with respiratory failure as a model of nutritional management in chronically critically ill patients. Nutritional assessment, methods of nutrient delivery, monitoring of nutritional therapy, and complications of nutritional support are discussed. Using this nutritional classification of respiratory failure, general principles of nutritional care can be applied to other critically ill patients. Finally, using this approach, the nutritional management of chronically critically ill patients is summarized.