[Malnutrition and chronic obstructive bronchopathies].

Abstract

A knowledge of the relationship between nutrition and the respiratory system applied in chronic airflow obstruction (BCO) enables a better understanding of the increased frequency (30 to 50%) of protein-energy malnutrition (MEP) in this population. The physiology of the wasting in chronic airflow obstruction seems to relate to hypermetabolism (HMB) which is not compensated by an increased alimentary intake. The HMB is linked to a rise in the work of the respiratory muscles whose efficiency is altered by intrathoracic hyperinfiltration and also the consequences of MEP on the mass and function of the respiratory muscles. In the animal MEP induced by alimentary restrictions leads to a model of pulmonary emphysema and to the diminution of the synthesis of surfactant. This emphysema seems to be principally due to an alteration of the process of protein synthesis and to a diminution of lysyl-oxydase activity. The nutrients (utilised notably by the venous route) have their own pharmacological role, and in addition they have an effect on the natural equilibrium of the energy and nitrogen balance. Lipids (rich in polyunsaturated fatty acids) intervene in the synthesis of prostaglandins, and exercise some effects on the inflammatory process and the activity in the bronchial and vascular smooth muscles. Based on this fact they have been used for their anti-inflammatory role at the pulmonary level in the treatment of mucoviscidosis. The administration of amino acids changes ventilation by acting on the central neuro-muscular command mechanism (VT/TI). The perfusion of amino acids enables a restoration of the chemo-sensitivity to oxygen and to CO2 abolished by the prolonged restricted diet. Finally the partial pressure of oxygen ought to be interpreted with respect to meal times because an oral dose of glucose can provoke an increase in the PaO2 of around 10 mmHg for healthy subjects and those with BCO. A preventive and therapeutic attitude vis a vis BCO should take account of the relationship between nutrition and the respiratory system in parallel with a correction of hypoxaemia in order to avoid the development of wasting.