Nutrition and Lung Disease

Abstract

“Let thy food be thy medicine and thy medicine be thy food.” Hippocrates (460–377 B.C.) Like Hippocrates, we realize that the nutrition we give patients is more than a source of calories. Unlike Hippocrates, we can consult an increasing body of literature that helps us address those areas where disease and nutrition intersect. This issue of Nutrition in Clinical Practice focuses on the delivery of nutrition to improve outcomes in patients with acute and chronic pulmonary illnesses. The reviews here examine many different strategies and outline the strengths and weaknesses of the supporting science. Like Hippocrates, we have yet much to learn and we must realize that his “primum non nocere” dictum also applies to nutrition science. For instance, immunonutrition appears to lower infectious complications in surgical patients, but may increase mortality in patients with sepsis. The blue dye practice for aspiration detection during enteral feeding was widely embraced before its poor specificity and potential for harm were appreciated, leading to an FDA Public Health Advisory. The discovery of such unexpected findings highlights the continued importance of randomized controlled trials to evaluate the efficacy and safety of nutritional interventions before we accept them as general practice. The safe and optimal provision of nutrition to patients with lung disease remains a challenge, and it is often unclear what nutritional approach is best. Optimizing nutrition in chronic lung diseases has mostly focused on preventing and treating malnourishment common to diseases such as emphysema and cystic fibrosis. Common diseases such as asthma are not often associated with malnutrition; we don’t have evidence that they benefit from specific dietary approaches. Chronic obstructive pulmonary disease (COPD) is the fourth largest cause of death in the United States, and a large subset of patients with moderate-to-severe COPD are underweight and malnourished, as Mallampalli points out in her review. No specific hormonal or nutritional regimen has been successful enough in these patients to be of routine use. The severity of underlying disease in COPD and the high metabolic rate needed to respire with diseased lungs currently precludes substantial benefit from dietary intervention in most patients. Yet the importance of the disease mandates continued investigation. The utility of specific formulas to minimize carbon dioxide production and thereby aid weaning in mechanically ventilated COPD patients also is poor. Such formulas should be used selectively. Olson and Schwenk show how an organized approach, advocacy, and clinical experience can minimize the malnutrition associated with cystic fibrosis, even in the absence of large trials. Yet it is difficult to control the diet of chronically ill patients. The potential benefit of dietary strategies is often negated by what patients will (or won’t) eat in their own homes. The provision of nutrition to acutely ill patients, many of whom are in intensive care units, creates unique challenges and is an area where the most impact may occur from specific nutritional strategies. Studies have shown that enteral nutrition is better than the parenteral route in acutely ill patients. However, scientific investigations have not always clarified the optimal timing, composition, delivery location, and means of avoiding complications when administering enteral nutrition, thus resulting in a wide variation in delivery practices. Most of this work has been done in adults and, as Carlson points out, the nutritional care of infants with lung disease has yet to be guided by large clinical trials. Once the decision is made to provide enteral nutrition, the first questions encountered are what type of tube should be used. Guidroz and Chaudhary discuss the advantages and disadvantages of many of the different tube types used for maintaining enteral access. Historically, placement of these tubes was preferentially trans-nasal, but appreciation of nasal tubes as risk factors for sinusitis now results in many trans-oral insertions, at least in intubated patients. Guidroz and Chaudry point out the many ways to initiate and maintain Correspondence: James P. Maloney, MD, Medical College of Wisconsin, 9200 West Wisconsin, Milwaukee, WI 53226. Electronic mail may be sent to jmaloney@mail.mcw.edu.