Hypoxia, nitrogen balance and body weight

Recent clinical studies have shown that acute exacerbations of chronic obstructive pulmonary disease (COPD) are characterised by disturbances in the balance between dietary intake and energy expenditure 1, 2 as well as by a negative nitrogen balance 3. Since weight loss prior to and during hospitalisation for an acute exacerbation has been related to poor outcome in terms of mortality and readmission rate 4, 5, it is important to prevent or treat this complication. It is yet unclear to what extent factors contributing to weight loss, during acute disease exacerbations, are similar to stable disease. Elevated energy requirement of physical activity has been implicated during stable disease 6 but is unlikely to be an important factor during acute disease, when the activity level is probably very low. Hypoxia is otherwise implicated as a potential trigger of reduced dietary intake and metabolic alterations during acute exacerbations, while in stable disease, there is no strong relationship between resting arterial oxygen tension and nutritional status. Hypobaric hypoxia, as applied in high-altitude studies, clearly induces weight loss and is an interesting human model to investigate the influence of acute hypoxia. There is evidence that the altitude limit for the maintenance of body weight in …