The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts


Julien M. Roy, BA, RRT

The facts are that there is a high incidence of malnutrition among our Pulmonary Rehab patients and malnourished patients have an increased susceptibility to infection resulting in an increased mortality and morbidity. Nutrition support helps to meet the caloric needs for respiration and structure and function of respiratory muscles. Hypercapnia which is often normal in COPD patients can be controlled by proper nutritional support. To better understand the need for better nutrition let me give you some pertinent observations to the nutritional care of COPD patients.

* Weight loss occurs in 25% to 65% of patients as a result of inadequate caloric intake due to anorexia, shortness of breath, or gastrointestinal distress and also due to the increased caloric requirements due to the excess work of breathing.

* We often forget that a normal individual require only 36 to 72 calories per day for his work of breathing compare to 430 to 720 calories per day for our average COPD patient in Rehab.

* When caloric intake is decreased, the body cannibalized muscles, including the respiratory muscles, to meet energy needs. As a consequence of malnutrition, the energy content and strength of respiratory muscles decrease.

* Semistarvation depresses hypoxic ventilatory response and as a result of starvation, production of pulmonary phospholipids and surfactant is reduced, and compliance of the lungs decreases.

* Malnutrition lowers resistance to infection, which is a common complication with most of our patients we see in Rehab.

Do I have your attention now! To move further into nutrition lets not overlook gas exchange and the respiratory quotient(RQ). Protein, fat, and carbohydrate are metabolic fuels that are converted into energy (heat) in the body. Fat and carbohydrate are converted completely to carbon dioxide(CO2) and water in the presence of oxygen(O2). The ratio of Co2 produced to O2 consumed is the respiratory quotient (RQ). The RQ produced by carbohydrate is 1.0, fat is 0.7, and protein is 0.8. For a given amount of O2 consumed, more CO2 is produced from metabolism of carbohydrate than fat or protein. Fat yield the lowest RQ least carbon dioxide for the amount of oxygen consumed. Since many of our patients have a tendency to consumed large amounts of carbohydrate like candy, cookies, etc... because it is quick and easy to eat in small amount result in higher RQ leading to increased carbon dioxide leading to increase shortness of breath. Since COPD patient have higher CO2 by nature the role of nutrition or therapy in general is to decrease it as much as possible. A diet high on unsaturated fat and low in carbohydrate will decrease CO2 production and lower RQ leading to diminished ventilatory requirements.

Here are some basic Dietary guidelines for COPD patients:

* Increase fat consumption (unsaturated fat) and decrease carbohydrate intake to reduce CO2 production and lower the respiratory quotient (RQ).

* Meet caloric requirements but do not exceed them, because overfeeding calories increases CO2 production.

* Avoid excessive protein intake because it may increase ventilatory drive in patients who have limited ability to respond.

* Monitor fluid requirements, restricting fluid intake as needed for patients with heart failure.

The recommended daily diet for COPD should be:

- 28% calorie intake from carbohydrates

- 55% calorie intake from Fat

- 12-20% calorie intake from protein

The 44th International Respiratory Congress Abstracts-On-DiskĀ®, November 7 - 10, 1998, Atlanta, Georgia.

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