Nutritional and pulmonary function assessment in chronic obstructive pulmonary disease: Effects of nutritional supplementation.

Introduction Weight loss or malnutrition occurs commonly in patients with severe chronic obstructive pulmonary disease (COPD) and those with malnutrition have been shown to have a greater rate of deterioration of lung function and a higher mortality.1–4 Malnourished COPD patients have been shown to have more respiratory muscle weakness and a more reduced maximal exercise capacity compared with wellnourished COPD patients with comparable severity of airways obstruction.5,6 The work of respiration is much increased in patients with severe COPD and this accounts for their marked increase in O2 cost of ventilation to levels several times higher than in normal subjects.7 The mechanism of malnutrition in COPD is not clear but the main basis is believed to be an inadequate dietary intake to meet the increased energy expenditure from respiratory work. Consequently, many investigators have attempted to increase the dietary intake of COPD patients by adding nutritional supplement to their normal diet in order to improve their weight, respiratory muscle strength, exercise capacity, and ultimately prognosis.5,8–11 Results, however, have not been encouraging and most studies of the giving of nutritional supplement to ambulatory patients with COPD have failed to deliver the anticipated benefit. In addition, instead of using only anthropometric measures as markers of malnutrition, which most studies have adopted, we used the resources of the Body Composition Laboratory of the Monash Medical Centre, Melbourne, Australia, with the techniques of in vivo neutron activation analysis (IVNAA) for measuring total body protein (TBP), and bioelectrical impedance analysis (BIA) for measuring body water and fat content. The aim of this study is to assess the body composition in subjects with severe COPD and low body weight. The effect of nutritional supplementation was reviewed. A prospective, randomized, double-blind and placebocontrolled study was conducted which considered changes of nutritional and respiratory parameters in malnourished patients with severe COPD in response to nutritional supplementation for 6 weeks. The use of a placebo is unusual in this type of study and this in turn allowed a double-blind design. Sophisticated methods of assessing body composition including in vivo neutron activation analysis (IVNAA) to measure total body protein (TBP) and bioelectric impedance analysis (BIA) to measure body water and fat content were applied to accurately assess body composition.