Physiological effects of intravenous fructose 1.6-diphosphate on diaphragmatic function in malnourished patients with COPD

Background. A low body mass index is one of the strongest predictors of mortality in Chronic Obstructive Pulmonary Disease (COPD) patients. Under-nutrition is often associated with skeletal muscle wasting and hypophosphatemia. Aim and Methods. In a pilot, randomised, doubleblind placebo-controlled study, we assessed the physiological effects of phosphorous administration in 17 stable undernourished COPD patients, on diaphragmatic function, breathing pattern, neuromuscular drive (P0.1) and dyspnea score. Fructose 1.6-diphosphate (FDP) or placebo was administered i.v. for 7 consecutive days. Results. FDP administration was associated with a marked increase in inspiratory time (Ti) that induced a significant rise (p<0.05) in the Pressure Time Product of the diaphragm per breath (PTPdi/b). However, since breathing frequency also decreased, the Pressure Time Product per minute of the diaphragm (PTPdi/min), index of diaphragmatic energy expenditure was markedly reduced. The efficiency of the respiratory pump in clearing CO2 was also improved, although not significantly, in the FDP group (p=0.09) as well as the maximal transdiaphragmatic pressure during the sniff manoeuvre (Pdi,sniff). Conclusions. This pilot physiological study showed that phosphorus replacement in undernourished, stable COPD patients, may be associated with a complex modification in respiratory pattern and diaphragmatic functions, leading to a marked although not significant reduction in PTPdi/min.